Gray scale inversion reduction or prevention in liquid crystal displays

Patent metadata

Field	Value
Publication number	US-10108049-B2
Application number	US-79462310-A
Country	US
Kind code	B2
Filing date	Jun 4, 2010
Priority date	Jun 4, 2010
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

Devices and methods related to high-contrast liquid crystal displays (LCDs) are provided. For example, such an electronic device may include an LCD with two liquid crystal alignment layers not symmetric to one another and upper and lower polarizing layers respectively above and below the alignment layers. Light transmittance through the plurality of pixels may increase monotonically with gray scale voltage. The display may operate using a gray scale level 0 voltage higher than a minimum gray scale level 0 voltage capability of the display. Additionally or alternatively, liquid crystal molecular alignment axes of the two alignment layers may be offset from one another by an angle other than a multiple of 180 degrees. Additionally or alternatively, a first polarizing axis of the upper polarizing layer or a second polarizing axis of the lower polarizing layer, or both, may be neither parallel nor perpendicular to one of the liquid crystal molecular alignment axes.

First claim

What is claimed is:

1. An electronic device comprising:
a liquid crystal display having a plurality of pixels with a liquid crystal material disposed between two liquid crystal alignment layers not symmetric to one another, and having upper and lower polarizing layers respectively above and below the two liquid crystal alignment layers, wherein light transmittance through the plurality of pixels increases monotonically as gray scale voltages increase and wherein:
the liquid crystal display is configured to operate using a gray scale level 0 voltage that is higher than a minimum gray scale level 0 voltage capability of the liquid crystal display; or
liquid crystal molecular alignment axes of the two liquid crystal alignment layers are offset from one another by an offset angle other than a multiple of 180 degrees; or
at least one of a first polarizing axis associated with the upper polarizing layer and a second polarizing axis associated with the lower polarizing layer is substantially nonparallel and substantially non-perpendicular to one of the liquid crystal molecular alignment axes of the two liquid crystal alignment layers to prevent or reduce gray scale inversion, wherein gray scale inversion causes light transmittance not to increase monotonically with all gray scale voltages, that would otherwise occur if the at least one of the first polarizing axis and the second polarizing axis were parallel or perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis; or
any combination thereof,

wherein the at least one of the first polarizing axis and the second polarizing axis substantially non-parallel and substantially non-perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis is offset from being parallel or perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis by an angle configured to cause the pixel to transmit a reduced amount of light in the absence of an electric field than that which would be transmitted by the pixel if both the first polarizing axis and the second polarizing axis were parallel or perpendicular to the first liquid crystal molecular alignment axis and the second liquid crystal molecular alignment axis in the absence of the electric field.

2. The electronic device of claim 1 , wherein at least one of the two liquid crystal alignment layers of the liquid crystal display is substantially non-planar.

3. The electronic device of claim 1 , wherein a first of the two liquid crystal alignment layers of the liquid crystal display is substantially planar and a second of the two liquid crystal alignment layers of the liquid crystal display is substantially non-planar, wherein a liquid crystal director azimuthal angle of the liquid crystal material is substantially aligned to a first liquid crystal molecular alignment axis associated with the first of the two liquid crystal alignment layers but is misaligned to a second liquid crystal molecular alignment axis associated with the second of the two liquid crystal alignment layers.

4. An electronic display comprising:
a pixel comprising:
a lower polarizing layer configured to polarize light on a first polarizing axis;
a lower liquid crystal alignment layer disposed above the lower polarizing layer and configured to generally align liquid crystal molecules along a first liquid crystal molecular alignment axis in the absence of an electric field;
liquid crystal layer disposed above the lower liquid crystal alignment layer that includes the liquid crystal molecules;
an upper liquid crystal alignment layer disposed above the liquid crystal layer and configured to generally align liquid crystal molecules along a second liquid crystal molecular alignment axis in the absence of an electric field, wherein the second liquid crystal molecular alignment axis is equal to or 180 degrees different from the first liquid crystal molecular alignment axis; and
an upper polarizing layer disposed above the upper liquid crystal alignment layer and configured to polarize light on a second polarizing axis;
wherein at least one of the first polarizing axis and the second polarizing axis is substantially non-parallel and substantially non-perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis to prevent or reduce gray scale inversion, wherein gray scale inversion causes light transmittance not to increase monotonically with all gray scale voltages, that would otherwise occur if the at least one of the first polarizing axis and the second polarizing axis were parallel or perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis,

wherein the at least one of the first polarizing axis and the second polarizing axis substantially non-parallel and substantially non-perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis is offset from being parallel or perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis by an angle configured to cause the pixel to transmit a reduced amount of light in the absence of an electric field than that which would be transmitted by the pixel if both the first polarizing axis and the second polarizing axis were parallel or perpendicular to the first liquid crystal molecular alignment axis and the second liquid crystal molecular alignment axis in the absence of the electric field.

5. The electronic display of claim 4 , wherein the at least one of the first polarizing axis and the second polarizing axis substantially non-parallel and substantially non-perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis is offset from being parallel or perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis by an angle less than five degrees.

6. The electronic display of claim 4 , wherein the at least one of the first polarizing axis and the second polarizing axis substantially non-parallel and substantially non-perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis is offset from being parallel or perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis by an angle of greater than 0.3 degrees and less than 1 degree.

7. The electronic display of claim 4 , wherein the lower liquid crystal alignment layer comprises protrusions into the liquid crystal layer and wherein, when the liquid crystal display is configured to operate in an O-mode, the first polarizing axis is offset from being parallel to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis in a direction toward being more parallel to the protrusions.

8. The electronic display of claim 4 , wherein the lower liquid crystal alignment layer comprises protrusions into the liquid crystal layer and wherein, when the liquid crystal display is configured to operate in an O-mode, the second polarizing axis is offset from being perpendicular to the first liquid crystal molecular alignment axis or the second liquid crystal molecular alignment axis in a direction toward being more perpendicular to the protrusions.

9. The electronic display of claim 4 , wherein the lower liquid crystal alignment layer comprises protrusions into the liquid crystal layer and wherein, when the liquid crystal display is con

Assignees

• Dorjgotov Enkhamgalan
• Ge Zhibing
• Xu Ming
• Chen Cheng
• Park Young Bae
• Zhong John Z
• Chen Wei
• Gettemy Shawn Robert
• Apple Inc

Inventors

• Dorjgotov Enkhamgalan
• Ge Zhibing
• Xu Ming
• Chen Cheng
• Park Young Bae
• Zhong John Z
• Chen Wei
• Gettemy Shawn Robert

Classifications

• G02F2001/133776

  Physics · mapped topic

• G02F1/133784 Primary

  by rubbing · CPC title

• G02F1/1337

  Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers · CPC title

• G09G3/36 Primary

  using liquid crystals · CPC title

• G02F1/133776

  having structures locally influencing the alignment, e.g. unevenness · CPC title