LCD panel having improved response

• US 8,294,850 B2
• Filed: 03/31/2009
• Issued: 10/23/2012
• Est. Priority Date: 03/31/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Cheng, Zhong, John Z., Xu, Ming, Gu, Mingxia
• Primary Examiner(s): Stahl, Mike
• Application Number:
  US12/415,848
• Publication Number:
  US 20100245723A1
• Time in Patent Office: 1,302 Days
• Field of Search: None
• US Class Current: 349/88
• CPC Class Codes: C09K 19/586 Optically active dopants; chiral dopants
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/134372 for fringe field switching [FFS] where the common electrode is not patterned
• CPC Class Codes: G02F 1/13775 Polymer-stabilized liquid crystal layers
• CPC Class Codes: G02F 1/1396 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell G02F1/141 takes precedence

Abstract

A liquid crystal display (LCD) having a liquid crystal layer is provided. In one embodiment, the liquid crystal layer includes a nematic liquid crystal material having liquid crystal molecules in an untwisted state. A chiral dopant is dispersed within the liquid crystal layer and configured to bias the liquid crystal molecules toward a twisted state. Furthermore, a polymer network is disposed among the liquid crystal molecules and configured to bias the liquid crystal molecules toward the untwisted state. Various additional devices and methods are also provided.

Claims

1. A liquid crystal display (LCD) panel, comprising:

a liquid crystal layer disposed between two substrates, the liquid crystal layer including;

a nematic liquid crystal material comprising a plurality of liquid crystal molecules in an untwisted state;

a right-handed chiral dopant dispersed within the nematic liquid crystal material and configured to bias the plurality of liquid crystal molecules in a right-handed direction while maintaining the liquid crystal molecules in the untwisted state; and

a polymer network disposed among the plurality of liquid crystal molecules and configured to bias the liquid crystal molecules toward the untwisted state.

2. The LCD panel of claim 1, wherein the LCD panel comprises a fringe field switching (FFS) LCD panel.

3. The LCD panel of claim 1, wherein the right-handed chiral dopant is less than about 1% of the liquid crystal layer by weight.

4. The LCD panel of claim 1, wherein the polymer network is less than about 10% of the liquid crystal layer by weight.

5. The LCD panel of claim 1, wherein a ratio of a thickness of the liquid crystal layer between the two substrates to a pitch of the right-handed chiral dopant is less than about 1.

6. The LCD panel of claim 1, wherein a ratio of a thickness of the liquid crystal layer between the two substrates to a pitch of the right-handed chiral dopant is between about 0.01 to 0.8.

7. An electronic device, comprising:

one or more input structures;

a storage structure encoding one or more executable routines;

a processor capable of receiving inputs from the one or more input structures and of executing the one or more executable routines when loaded in a memory; and

a liquid crystal display (LCD) capable of displaying an output of the processor, wherein the LCD includes;

a pixel electrode;

a common electrode disposed adjacent to a first side of the pixel electrode; and

a liquid crystal layer disposed adjacent to a second side of the pixel electrode, the second side being substantially opposite from the first side, wherein the liquid crystal layer comprises a plurality of liquid crystal molecules in an untwisted state;

wherein the plurality of liquid crystal molecules are configured to twist in response to an electrical field generated between the pixel electrode and the common electrode, and wherein the liquid crystal layer comprises a chiral dopant configured to bias the plurality of liquid crystal molecules toward a twisted state while permitting the plurality of liquid crystal molecules to remain in the untwisted state until the electrical field is applied.

8. The electronic device of claim 7, wherein the chiral dopant enables reduction of a response time of the LCD at a given driving voltage.

9. The electronic device of claim 7, wherein the chiral dopant enables reduction of a driving voltage of the LCD while maintaining a response time of the LCD.

10. The electronic device of claim 7, comprising a polymer network disposed within the liquid crystal layer.

11. The electronic device of claim 10, wherein the polymer network is configured to reduce a response time of the LCD.

12. A display panel comprising:

a liquid crystal layer having a thickness and a plurality of liquid crystal molecules configured to transition between an untwisted state that inhibits transmission of light through the display panel and a twisted state that facilitates transmission of light through the display panel, wherein the liquid crystal layer includes an amount of chiral dopant sufficient to bias the liquid crystal molecules toward the twisted state but less than that which would effect rotation of the liquid crystal molecules toward the twisted state in the absence of an electrical field.

13. The display panel of claim 12, wherein the chiral dopant is less than about 0.20% of the liquid crystal layer by weight.

14. The display panel of claim 12, wherein the chiral dopant is between about 0.05% and 0.75% of the liquid crystal layer by weight.

15. The display panel of claim 12, wherein a ratio of the thickness to a pitch of the chiral dopant is between about 0.05 and 0.55.

16. A liquid crystal display (LCD) panel comprising:

a liquid crystal layer having a plurality of liquid crystal molecules configured to transition between an untwisted state that inhibits transmission of light through the LCD panel and a twisted state that facilitates transmission of light through the LCD panel, wherein the liquid crystal layer includes an amount of chiral dopant sufficient to bias the liquid crystal molecules toward the twisted state but less than that which would effect rotation of the liquid crystal molecules toward the twisted state in the absence of an electrical field, and a polymer network configured to bias the liquid crystal molecules toward the untwisted state.

17. The LCD panel of claim 16, wherein the polymer network is less than about 20% of the liquid crystal layer by weight.

18. The LCD panel of claim 16, wherein the polymer network is between about 1% and 15% of the liquid crystal layer by weight.

19. The LCD panel of claim 16, wherein the chiral dopant is configured to reduce a response time of the LCD panel.

20. The LCD panel of claim 16, wherein the polymer network increases the tolerance of the LCD panel to mechanical distortion.

21. A method of manufacturing a fringe field switching (FFS) liquid crystal display (LCD) panel, the method comprising:

forming a liquid crystal layer, wherein forming the liquid crystal layer comprises;

disposing nematic liquid crystal material between a plurality of alignment layers, wherein the nematic liquid crystal material comprises a plurality of liquid crystal molecules in an untwisted state;

dispersing an amount of chiral dopant within the nematic liquid crystal material sufficient to bias the plurality of liquid crystal molecules toward a twisted state while maintaining the liquid crystal molecules in the untwisted state, wherein the chiral dopant is configured to reduce a response time of the FFS LCD panel; and

forming a polymer network within the liquid crystal layer, wherein the polymer network is also configured to reduce the response time of the FFS LCD panel.

22. The method of claim 21, wherein the chiral dopant is dispersed within the nematic liquid crystal material prior to disposing the nematic liquid crystal material between the plurality of alignment layers.

23. The method of claim 21, wherein forming the polymer network comprises dispersing a pre-polymer solution within the liquid crystal layer prior to disposing the nematic liquid crystal material between the plurality of alignment layers.

24. The method of claim 23, wherein forming the polymer network comprises polymerizing the pre-polymer solution after dispersing the chiral dopant within the nematic liquid crystal material.

25. The method of claim 21, wherein disposing the nematic liquid crystal material between the plurality of alignment layers comprises disposing the nematic liquid crystal material on a first alignment layer and disposing a second alignment layer on the nematic liquid crystal material.