Low power consumption transflective liquid crystal displays

• US 8,698,716 B2
• Filed: 05/18/2010
• Issued: 04/15/2014
• Est. Priority Date: 05/18/2010
• Status: Active Grant

• Current Assignee: John Gilmore
• Original Assignee: Pixel Qi Corporation
• Inventors: Lu, Ruibo, Jepsen, Mary Lou
• Primary Examiner(s): Moorad, Waseem
• Application Number:
  US12/782,574
• Publication Number:
  US 20110285684A1
• Time in Patent Office: 1,428 Days
• Field of Search: None
• US Class Current: 345/87
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n

Abstract

Techniques are provided to drive a normally white or mixed mode LCD with low voltages and low power consumption. A sub-pixel in the LCD may comprise a reflective part and a transmissive part. The cell gap for a liquid crystal layer in the sub-pixel may provide at least a half-wave phase retardation. A driving voltage range with a maximum voltage at a low value may be used to drive the reflective part and the transmissive part of the sub-pixel to various levels of brightness.

Claims

1. A transflective liquid crystal display comprising a plurality of sub-pixels, each sub-pixel comprising:

a reflective part, comprising;

first portions of a first retardation film, a first polarizing layer, a bottom substrate layer, a top substrate layer, and a common electrode portion, wherein the top substrate layer is opposite to the bottom substrate layer;

a reflective layer adjacent to the bottom substrate layer;

a reflective-part liquid crystal layer portion of a liquid crystal layer between the bottom substrate layer and the top substrate layer;

a transmissive part, comprising;

second portions of the first retardation film, the first polarizing layer, the bottom substrate layer, the top substrate layer, and the common electrode portion;

a transmissive-part liquid crystal layer portion of the liquid crystal layer between the bottom substrate layer and the top substrate layer;

wherein a transmissive-part cell gap of the transmissive-part liquid crystal layer portion is configured as a plate of at least a half-wavelength or more in a voltage-off state of the transmissive-part liquid crystal layer portion;

wherein said each sub-pixel is normally-white at a voltage-off state.

2. The transflective liquid crystal display according to claim 1, wherein the transmissive-part liquid crystal layer portion is configured to be driven to a transmissive display state by 1.0 volt at maximum to 2.7 volts at maximum.

3. The transflective liquid crystal display according to claim 1, wherein the reflective-part liquid crystal layer portion is configured to be driven to a reflective display state by 1.0 volt at maximum to 2.7 volts at maximum.

4. The transflective liquid crystal display according to claim 1, wherein the reflective-part liquid crystal layer portion comprises liquid crystal molecules that are homogeneously aligned along a second direction in the voltage-off state of the reflective-part liquid crystal layer portion.

5. The transflective liquid crystal display according to claim 1, wherein the transmissive part further comprises a portion of a second retardation film.

6. The transflective liquid crystal display according to claim 1, wherein the reflective part further comprises an over-coating layer adjacent to one of the bottom substrate layer and the top substrate layer, wherein the over-coating layer is between the bottom substrate layer and the top substrate layer, and wherein a reflective-part cell gap of the reflective-part liquid crystal layer portion is a plate of a half-wavelength or more in a voltage-off state of the reflective-part liquid crystal layer portion.

7. The transflective liquid crystal display according to claim 1, wherein a reflective-part cell gap of the reflective-part liquid crystal layer portion is equal to the transmissive-part cell gap.

8. The transflective liquid crystal display according to claim 1, wherein the reflective-part liquid crystal layer portion is configured to be driven to a reflective display state by a first voltage and wherein the transmissive-part liquid crystal layer portion is configured to be driven to a transmissive display state by the first voltage.

9. The transflective liquid crystal display according to claim 1, wherein the reflective-part liquid crystal layer portion is configured to be driven to a reflective display state by a first voltage and wherein the transmissive-part liquid crystal layer portion is configured to be driven to a transmissive display state by a second, different, voltage.

10. The transflective liquid crystal display according to claim 1, wherein the sub-pixel further comprises at least one color filter that covers at least a portion of the transmissive part sub-pixel.

11. The transflective liquid crystal display according to claim 10, wherein the sub-pixel is a part of a composite pixel, and wherein the composite pixel comprises another sub-pixel that is configured to express a different color than the sub-pixel.

12. The transflective liquid crystal display according to claim 1, wherein a normal direction of the bottom substrate layer is parallel to the first direction or to the second direction.

13. The transflective liquid crystal display according to claim 1, wherein the sub-pixel further comprises one or more orientation films and wherein one or more of the first direction and the second direction are along a rubbing direction of at least one of the one or more orientation films.

14. The transflective liquid crystal display according to claim 1, wherein optical birefringence of the liquid crystal layer is electrically controllable.

15. The transflective liquid crystal display according to claim 1, wherein the first retardation film has an azimuth angle of θ

_h, wherein the transmit-part liquid crystal layer portion has an azimuth angle of θ

_q, and wherein the azimuth angles satisfy one of;

60≦

4θ

_h−

2θ

_q≦

120, or −

120≦

4θ

_h−

2θ

_q≦

−

60.

16. The transflective liquid crystal display according to claim 1, wherein the reflective part comprises a reflective electrode, wherein the transmissive part comprises a transmissive electrode, and wherein the sub-pixel comprises a switching element that is configured to control whether the reflective electrode is electrically connected to the transmissive electrode.

17. The transflective liquid crystal display according to claim 1, wherein the reflective part comprises a reflective electrode, wherein the transmissive part comprises a transmissive electrode, wherein the common electrode is located on a first side of the liquid crystal layer, and wherein the transmissive electrode and the reflective electrode are located on a second opposing side of the liquid crystal layer.

18. The transflective liquid crystal display according to claim 1, wherein the sub-pixel further comprises a light recycling film between the bottom substrate layer and a backlight unit that redirects backlight from the reflective part to the transmissive part.

19. The transflective liquid crystal display according to claim 18, wherein the light recycling film is configured to turn incident light of any polarized state into redirected light with a particular polarization state.

20. The transflective liquid crystal display according to claim 1, wherein the transmissive part liquid crystal layer portion comprises homogeneously aligned liquid crystal molecules.

21. A computing device, comprising:

one or more processors;

a transflective liquid crystal display comprising a plurality of sub-pixels, each sub-pixel comprising;

a reflective part, comprising;

first portions of a first retardation film, a first polarizing layer, a bottom substrate layer, a top substrate layer, and a common electrode portion, wherein the top substrate layer is opposite to the bottom substrate layer;

a reflective layer adjacent to the bottom substrate layer;

a reflective-part liquid crystal layer portion of a liquid crystal layer between the bottom substrate layer and the top substrate layer;

a transmissive part, comprising;

second portions of the first retardation film, the first polarizing layer, the bottom substrate layer, the top substrate layer, and the common electrode portion;

a transmissive-part liquid crystal layer portion of the liquid crystal layer between the bottom substrate layer and the top substrate layer;

wherein a transmissive-part cell gap of the transmissive-part liquid crystal layer portion is configured as a plate of at least a half-wavelength or more in a voltage-off state of the transmissive-part liquid crystal layer portion;

wherein said each sub-pixel is normally-white at a voltage-off state.

22. The computer device according to claim 21, wherein the transmissive-part liquid crystal layer portion is configured to be driven to a transmissive display state by 1.0 volt at maximum to 2.7 volts at maximum.

23. The computer device according to claim 21, wherein the reflective-part liquid crystal layer portion is configured to be driven to a reflective display state by 1.0 volt at maximum to 2.7 volts at maximum.

24. The computer device according to claim 21, wherein the reflective-part liquid crystal layer portion comprises liquid crystal molecules that are homogeneously aligned along a second direction in the voltage-off state of the reflective-part liquid crystal layer portion.

25. The computer device according to claim 21, wherein the transmissive part further comprises a portion of a second retardation film.

26. The computer device according to claim 21, wherein the reflective part further comprises an over-coating layer adjacent to one of the bottom substrate layer and the top substrate layer, wherein the over-coating layer is between the bottom substrate layer and the top substrate layer, and wherein a reflective-part cell gap of the reflective-part liquid crystal layer portion is a plate of a half-wavelength or more in a voltage-off state of the reflective-part liquid crystal layer portion.

27. The computer device according to claim 21, wherein a reflective-part cell gap of the reflective-part liquid crystal layer portion is equal to the transmissive-part cell gap.

28. The computer device according to claim 21, wherein the sub-pixel further comprises a light recycling film between the bottom substrate layer and a backlight unit that redirects backlight from the reflective part to the transmissive part.

29. A method of fabricating a transflective liquid crystal display, comprising:

providing a plurality of pixels, a pixel comprising;

a reflective part, comprising;

first portions of a first retardation film, a first polarizing layer, a bottom substrate layer, a top substrate layer, and a common electrode portion, wherein the top substrate layer is opposite to the bottom substrate layer;

a reflective layer adjacent to the bottom substrate layer;

a reflective-part liquid crystal layer portion of a liquid crystal layer between the bottom substrate layer and the top substrate layer;

a transmissive part, comprising;

second portions of the first retardation film, the first polarizing layer, the bottom substrate layer, the top substrate layer, and the common electrode portion;

a transmissive-part liquid crystal layer portion of the liquid crystal layer between the bottom substrate layer and the top substrate layer;

wherein a transmissive-part cell gap of the transmissive-part liquid crystal layer portion is configured as a plate of at least a half-wavelength or more in a voltage-off state of the transmissive-part liquid crystal layer portion;

wherein said each sub-pixel is normally-white at a voltage-off state.

30. The method according to claim 29, wherein the transmissive-part liquid crystal layer portion is configured to be driven to a transmissive display state by 1.0 volt at maximum to 2.7 volts at maximum.

31. The method according to claim 29, wherein the reflective-part liquid crystal layer portion is configured to be driven to a reflective display state by 1.0 volt at maximum to 2.7 volts at maximum.