Wide viewing angle transflective liquid crystal displays

• US 7,589,808 B2
• Filed: 06/15/2007
• Issued: 09/15/2009
• Est. Priority Date: 06/15/2007
• Status: Expired due to Fees

• Current Assignee: InnoLux Corporation, University of Central Florida Research Foundation Inc. (State University System of Florida)
• Original Assignee: Chi Mei Optoelectronics (InnoLux Corporation), University of Central Florida Research Foundation Inc. (State University System of Florida)
• Inventors: Li, Wang-Yang, Ge, Zhibing, Wu, Shin-Tson, Wei, Chung-Kuang, Wu, Thomas Xinzhang
• Primary Examiner(s): KIM, ELLEN E
• Application Number:
  US11/763,894
• Publication Number:
  US 20080309853A1
• Time in Patent Office: 823 Days
• Field of Search: 349/96, 349/113, 349/114, 349/187
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133548 Wire-grid polarisers
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

Apparatus, methods and systems for a transmissive liquid crystal display including a plurality of pixel circuits, each pixel circuit including a reflective region and a transmissive region. The reflective region includes a polarization dependent reflector for reflecting ambient light. The reflective and transmissive regions include an initially homogeneously aligned liquid crystal layer sandwiched between a first and a second substrate. Each pixel further includes at least one first transparent electrode as the common electrode and at least one second transparent electrode as the pixel electrode both formed on one of the same first and second substrates, wherein substantial fringe fields with rich horizontal electric fields are generated in the liquid crystal layer when voltage is applied to the pixel electrode, making the liquid crystal molecules rotate mainly in the horizontal direction to achieve wide viewing angle.

Claims

1. A transflective liquid crystal display device comprising:

a plurality of pixel circuits sandwiched between a first substrate and a second substrate, each pixel circuit comprising;

a reflective region comprising a first portion of a liquid crystal layer and a polarization dependent reflector that transmits light having a first polarization and reflects light having a second polarization;

a transmissive region comprising a second portion of the liquid crystal layer;

at least one transparent common electrode formed on the inner surface of one of the first and second substrate; and

at least one transparent pixel electrode formed on an outer surface of the same substrate as the common electrode, the at least one common electrode and at least one

pixel electrode insulated by a passivation layer therebetween;

the liquid crystal molecules in the reflective and transmissive regions are substantially aligned along a direction parallel to the first and second substrate when no voltage is applied to the at least one common and at least one pixel electrodes, and horizontal electric fields that are substantially parallel to the first and second substrate are generated in the liquid crystal layer to rotate liquid crystal molecules substantially in a plane parallel to the first and second substrate, when a high voltage is applied to the pixel electrode.

2. The display of claim 1 wherein the common electrode is a plane electrode.

3. The display of claim 1 wherein the pixel electrode comprises:

at least two electrode strips that are parallel to each other having an electrode width between approximately 1 μ

m and approximately 6 μ

m and a gap between adjacent strips between approximately 1 μ

m and approximately 10 μ

m.

4. The display of claim 3 wherein a shape of each of the at least two pixel electrode strips is selected from a group consisting of straight, curved, and piecewise linear shapes.

5. The display of claim 3 wherein the electrode width and the gap between adjacent pixel electrode strips are approximately equal in the reflective region and transmissive region.

6. The display of claim 3 wherein the electrode width and the gap between adjacent pixel electrode strips in the reflective region is different than the electrode width and gap between adjacent pixel electrode strips in the transmissive region.

7. The display of claim 1 wherein the at least one common electrode and at least one pixel electrode are made of one of an indium tin oxide, indium zinc oxide, and gallium zinc oxide material.

8. The display of claim 1 wherein the passivation layer is one of a silicon dioxide and silicon nitride material.

9. The display of claim 1, further comprising:

a first linear polarizer on an outer surface of the first substrate; and

a second linear polarizer on an outer surface of the second substrate, wherein the first and the second linear polarizer extend over the transmissive and reflective regions.

10. The display of claim 9 wherein the first linear polarizer has a transmission axis perpendicular to the transmission of the second linear polarizer.

11. The display of claim 9 wherein the first linear polarizer is located adjacent to a viewer than the second linear polarizer and the polarization dependent reflector has a reflective axis perpendicular to the transmission axis of the first linear polarizer.

12. The display of claim 9 wherein the polarization dependent reflector comprises:

a wire grid polarizer.

13. The display of claim 12 wherein the reflection axis of the polarization dependent reflector is perpendicular to the transmission axis of one of the first linear polarizer that is closer to the viewer.

14. The display of claim 1 wherein the polarization dependent reflector comprises:

a wire grid polarizer.

15. The display of claim 1 wherein the liquid crystal layer sandwiched between the first and second substrates has a rubbing direction parallel to the transmission axis of the first linear polarizer.

16. The display of claim 1 wherein the liquid crystal layer sandwiched between the first and second substrates has a rubbing direction perpendicular to the transmission axis of the first second polarizer.

17. The display of claim 1 wherein the liquid crystal layer comprises:

a negative dielectric anisotropic liquid crystal material.

18. The display of claim 1 wherein the liquid crystal layer comprises:

a positive dielectric anisotropic liquid crystal material.

19. The display of claim 17 wherein the pixel electrode comprises:

at least two pixel electrode strips each having a lengthwise strip direction that forms a cross angle within a range of approximately 45° and

approximately 90°

with respect to a lengthwise direction of a rubbing axis of the negative dielectric anisotropic liquid crystal material.

20. The display of claim 18 wherein the pixel electrode comprises:

at least two pixel electrode strips each having a lengthwise strip direction that forms a cross angle within a range between 0° and

approximately 45°

with respect a lengthwise direction of a rubbing axis of the positive dielectric anisotropic liquid crystal material.