Wide Viewing Angle and Broadband Circular Polarizers for Transflective Liquid Crystal Displays

• US 20080309854A1
• Filed: 06/15/2007
• Published: 12/18/2008
• Est. Priority Date: 06/15/2007
• Status: Abandoned Application

• Current Assignee: InnoLux Corporation, University of Central Florida Research Foundation Inc. (State University System of Florida)
• Original Assignee: InnoLux Corporation
• Inventors: Li, Wang-Yang, Lu, Ruibo, Ge, Zhibing, Wu, Shin-Tson, Wei, Chung-Kuang, Wu, Thomas Xinzhang, Jiao, Meizi
• Application Number:
  US11/763,839
• Publication Number:
  US 20080309854A1
• Time in Patent Office: Days
• US Class Current: 349/98
• CPC Class Codes: G02F 1/133541 Circular polarisers
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2203/09 transflective
• CPC Class Codes: G02F 2413/04 Number of plates greater than or equal to 4
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation
• CPC Class Codes: G02F 2413/13 Positive birefingence
• CPC Class Codes: G02F 2413/14 Negative birefingence

Abstract

Apparatus, devices, systems, and methods for wide viewing angle and broadband circular polarizers in transflective displays. A liquid crystal display configuration can include two stacked circular polarizers, each having a linear polarizer, a half-wave plate and a quarter-wave plate wherein two linear polarizers are crossed to each other, two half-wave plates are made of uniaxial A plates with opposite optical birefringence (one positive and one negative type), and two quarter-wave plates are made of uniaxial A plates with opposite optical birefringence (one positive and one negative type). The configurations can generate wide viewing angles and broadband properties and are suitable for display applications that require circular polarizers.

Claims

1. A liquid crystal display device comprising:

a first transparent substrate;

a second transparent substrate;

a liquid crystal cell having a liquid crystal layer sandwiched between the first and the second transparent substrates;

a first circular polarizer disposed behind a viewer'"'"'s side of the liquid crystal layer;

wherein the first polarizer further includes a first linear polarizer, a first half-wave plate, a first quarter-wave plate;

a second circular polarizer disposed on the viewer'"'"'s side of the liquid crystal layer;

wherein the second polarizer includes a second linear polarizer, a second half-wave plate, and a second quarter-wave plate;

at least one optical retardation compensator disposed between the first circular polarizer and the second circular polarizer;

wherein the first half-wave plate and the first quarter-wave plate are positioned between the inner surface of the first linear polarizer and the liquid crystal layer, having the first half-wave plate closer to the first polarizer than the first quarter-wave plate; and

the second half-wave plate and the second quarter-wave plate are positioned between the inner surface of the second linear polarizer and the liquid crystal layer, having the second half-wave plate closer to the second polarizer than the second quarter-wave plate;

wherein the first half-wave plate and the second half-wave plate are made of uniaxial A plates with opposite optical birefringence; and

the first quarter-wave plate and the second quarter-wave plate are made of uniaxial A plates with opposite optical birefringence; and

a switching means applied to the liquid crystal layer for switching the phase retardation of the liquid crystal layer between a zero and a half-wave plate value for attaining different gray levels.

2. The display of claim 1 wherein the first linear polarizer and the second linear polarizer include dichroic polymer films that have transmission axis perpendicular to each other.

3. The display of claim 2, wherein the dichroic polymer films include:

a polyvinyl-alcohol-based film.

4. The display of claim 1, wherein the first half-wave plate in the first circular polarizer that is away from the viewer includes a positive uniaxial A plate, the first quarter-wave plate includes a negative uniaxial A plate, the second half-wave plate includes a negative uniaxial A plate, and the second quarter-wave plate includes a positive uniaxial A plate.

5. The display of claim 4, wherein the positive and negative uniaxial A plates include:

at least one of a polymer layer or a homogenous liquid crystal film.

6. The display of claim 1 wherein the first half-wave plate in the first circular polarizer that is away from the viewer includes a negative uniaxial A plate, the first quarter-wave plate includes a positive uniaxial A plate;

the second half-wave plate includes a positive uniaxial A plate and the second quarter-wave plate includes of negative uniaxial A plate.

7. The display of claim 6, wherein the positive and negative uniaxial A plates include:

at least one of a polymer layer or a homogenous liquid crystal film.

8. The display of claim 4, wherein the optic axis of the second half-wave plate is set at an angle from −

30°

to −

5°

with respect to the transmission axis of the second linear polarizer, that is closer to the viewer;

the second quarter-wave plate has its optic axis set at from approximately −

15°

to approximately +35°

with respect to the transmission axis of the second linear polarizer, correspondingly;

the first half-wave plate has its optic axis angle set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer; and

the first quarter-wave plate has its optic axis angle at an angle from approximately −

15°

to approximately +35°

with respect to the transmission axis of the second linear polarizer, with respect to the transmission axis of the second linear polarizer.

9. The display of claim 6, wherein the optic axis of the second half-wave plate is set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer, that is closer to the viewer;

the second quarter-wave plate has its optic axis set at from approximately −

15°

to approximately +35°

with respect to the transmission axis of the second linear polarizer, correspondingly;

the first half-wave plate has its optic axis angle set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer; and

the first quarter-wave plate has its optic axis angle at an angle from approximately −

15°

to approximately +35°

with respect to the transmission axis of the second linear polarizer, with respect to the transmission axis of the second linear polarizer.

10. The display of claim 4, wherein the optic axis of the half-wave plate is set at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer that is closer to the viewer, the second quarter-wave plate has its optic axis set at from approximately −

35°

to approximately +15°

with respect to the transmission axis of the second linear polarizer, correspondingly, the first half-wave plate has its optic axis angle at an angle from approximately −

+5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer, and the first quarter-wave plate has its optic axis angle set at an angle from approximately −

35°

to approximately +15°

with respect to the transmission axis of the second linear polarizer, with respect to the transmission axis of the second linear polarizer.

11. The display of claim 6, wherein the optic axis of the half-wave plate is set at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer that is closer to the viewer, the second quarter-wave plate has its optic axis set at from approximately −

35°

to approximately +15°

with respect to the transmission axis of the second linear polarizer, correspondingly, the first half-wave plate has its optic axis angle at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer, and the first quarter-wave plate has its optic axis angle set at an angle from approximately −

35°

to approximately +15°

with respect to the transmission axis of the second linear polarizer, with respect to the transmission axis of the second linear polarizer.

12. The display of claim 1, wherein the first half-wave plate includes a positive uniaxial A plate, the first quarter-wave plate includes a positive uniaxial A plate, the second half-wave plate includes a negative uniaxial A plate, and the second quarter-wave plate includes a negative uniaxial A plate.

13. The display of claim 12, wherein the positive and negative uniaxial A plates include:

at least one of a polymer layer or a homogenous liquid crystal film.

14. The display of claim 1 wherein the first half-wave plate includes a negative uniaxial A plate, the first quarter-wave plate includes a negative uniaxial A plate;

the second half-wave plate includes a positive uniaxial A plate and the second quarter-wave plate includes a positive uniaxial A plate.

15. The display of claim 14, wherein the positive and negative uniaxial A plates include:

at least one of a polymer layer or a homogenous liquid crystal film.

16. The display of claim 12, wherein the optic axis of the second half-wave plate is set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer that is closer to the viewer, the second quarter-wave plate has its optic axis set at from approximately −

15°

to approximately +35°

with respect to the transmission axis of the first linear polarizer that is away from the viewer correspondingly, the first half-wave plate has its optic axis angle set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer, and the first quarter-wave plate has its optic axis angle at an angle from approximately −

15°

to approximately +35°

with respect to the transmission axis of the first linear polarizer, with respect to the transmission axis of the second linear polarizer.

17. The display of claim 14, wherein the optic axis of the second half-wave plate is set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer that is closer to the viewer, the second quarter-wave plate has its optic axis set at from approximately −

15°

to approximately +35°

with respect to the transmission axis of the first linear polarizer that is away from the viewer correspondingly, the first half-wave plate has its optic axis angle set at an angle from approximately −

30°

to approximately −

5°

with respect to the transmission axis of the second linear polarizer, and the first quarter-wave plate has its optic axis angle at an angle from approximately −

15°

to approximately +35°

with respect to the transmission axis of the first linear polarizer, with respect to the transmission axis of the second linear polarizer.

18. The display of claim 12, wherein the optic axis of the second half-wave plate is set at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer that is closer to the viewer, the second quarter-wave plate has its optic axis set at from approximately −

35°

to approximately +15°

with respect to the transmission axis of the first linear polarizer that is away from the viewer correspondingly, the first half-wave plate has its optic axis angle set at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer, and the first quarter-wave plate has its optic axis angle set at an angle from approximately −

35°

to approximately +15°

with respect to the transmission axis of the first linear polarizer, with respect to the transmission axis of the second linear polarizer.

19. The display of claim 14, wherein the optic axis of the second half-wave plate is set at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer that is closer to the viewer, the second quarter-wave plate has its optic axis set at from approximately −

35°

to approximately +15°

with respect to the transmission axis of the first linear polarizer that is away from the viewer correspondingly, the first half-wave plate has its optic axis angle set at an angle from approximately +5°

to approximately +30°

with respect to the transmission axis of the second linear polarizer, and the first quarter-wave plate has its optic axis angle set at an angle from approximately −

35°

to approximately +15°

with respect to the transmission axis of the first linear polarizer, with respect to the transmission axis of the second linear polarizer.

20. The display of claim 1, wherein the at least one optical retardation compensator is laminated between the liquid crystal layer and one of the first and second circular polarizers.

21. The display of claim 20, wherein the optical retardation compensator includes:

a negative C film.

22. The display of claim 20, wherein the optical retardation compensator includes:

a negative C film having a total phase retardation value (dΔ

n) between approximately −

400 nm to approximately −

250 nm.

23. The display of claim 1 wherein the liquid crystal cell is a transmissive liquid crystal cell.

24. The display of claims 23, wherein the liquid crystal layer is selected from a group consisting of:

a vertically aligned cell, electrically controlled birefringence cell, and an optically compensated birefringence cell.

25. The display of claim 1 wherein the liquid crystal cell is a transflective liquid crystal display.

26. The display of claim 25, wherein the transflective display includes:

a first transparent substrate;

a second transparent substrate;

a liquid crystal cell;

a first circular polarizer, wherein the first polarizer further includes a first linear polarizer, a first half-wave plate, a first quarter-wave plate;

a second circular polarizer, wherein the second polarizer includes a second linear polarizer, a second half-wave plate, and a second quarter-wave plate; and

the second circular polarizer located closer to the front side of the display than the first circular polarizer; and

pixel circuits between the first and second substrates, each of the pixel circuits having a transmissive portion and a reflective portion, wherein the reflective portion includes a reflector for reflecting the external light, and the transmissive portion includes a transmitter to modulate light generated by an internal light source.

27. The display of claim 25, wherein the transflective display includes:

a first transparent substrate;

a second transparent substrate;

a first circular polarizer, wherein the first polarizer further comprises of a first linear polarizer, a first half-wave plate, a first quarter-wave plate;

a second circular polarizer, wherein the second polarizer comprises of a second linear polarizer, a second half-wave plate, and a second quarter-wave plate; and

the second circular polarizer located closer to the front side of the display than the first circular polarizer;

a liquid crystal layer, in which a portion of the liquid crystal layer is used to modulate light when the display is operating in a transmissive mode, and the same portion of the liquid crystal layer is used to modulate light when the display is operating in a reflective mode, and

28. The display of claim 26, wherein the first half-wave plate and the first quarter-wave plate are positioned between the inner surface of the first linear polarizer and the liquid crystal layer having the first half-wave plate closer to the first linear polarizer, and the second half-wave plate and the second quarter-wave plate are positioned between the inner surface of the second linear polarizer and the liquid crystal layer having the second half-wave plate closer to the second linear polarizer, and the first half-wave plate and the second half-wave plate are made of uniaxial A plates and are configured with opposite optical birefringence, and the first quarter-wave plate and the second quarter-wave plate are made of uniaxial A plates and are configured with opposite optical birefringence.

29. The display of claim 27, wherein the first half-wave plate and the first quarter-wave plate are positioned between the inner surface of the first linear polarizer and the liquid crystal layer having the first half-wave plate closer to the first linear polarizer, and the second half-wave plate and the second quarter-wave plate are positioned between the inner surface of the second linear polarizer and the liquid crystal layer having the second half-wave plate closer to the second linear polarizer, and the first half-wave plate and the second half-wave plate are made of uniaxial A plates and are configured with opposite optical birefringence, and the first quarter-wave plate and the second quarter-wave plate are made of uniaxial A plates and are configured with opposite optical birefringence.

30. A liquid crystal display device comprising:

a first broadband circular polarizer;

a second broadband circular polarizer, the first broadband circular polarizer being stacked on the second broadband circular polarizer;

a liquid crystal cell; and

an optical retardation compensator, wherein the liquid crystal cell and the optical retardation compensator are sandwiched between the first and the second broadband circular polarizers.

31. The liquid crystal display device of claim 30, wherein each of the first and the second broadband circular polarizers includes:

a linear polarizer;

a half-wave plate and

a quarter-wave plate, wherein the half-wave plate is between the linear polarizer and the quarter-wave plate, and the two half-wave plates are made of uniaxial A films with opposite optical birefringence and the two quarter-wave plates are made of uniaxial A films with opposite optical birefringence.

32. The liquid crystal display device of claim 30, further comprising:

a switching means applied to the liquid crystal layer for switching the phase retardation compensator between a zero and a half-wave plate value for attaining different gray levels.