Field Sequential Color Ferroelectric Liquid Crystal Display Cell

• US 20140118650A1
• Filed: 11/01/2013
• Published: 05/01/2014
• Est. Priority Date: 11/01/2012
• Status: Active Grant

• Current Assignee: Hong Kong University of Science and Technology
• Original Assignee: Hong Kong University of Science and Technology
• Inventors: CHIGRINOV, Vladimir Grigorievich, KWOK, Hoi Sing, SRIVASTAVA, Abhishek Kumar, MA, Ying
• Granted Patent: US 9,366,934 B2
• Time in Patent Office: Days
• US Class Current: 349/41
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G09G 2300/0404 Matrix technologies
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 3/36 using liquid crystals

Abstract

A field sequential color (FSC) ferroelectric liquid crystal (FLC) display cell, part of an FSC display, is provided. The FSC FLC display cell includes: two polarizers; an FLC layer, positioned between the two polarizers, the FLC layer comprising FLCs with helix pitch less than the thickness of the FLC layer; and a voltage source, configured to apply an electrical driving voltage to the FLC layer, the electrical driving voltage applied to the FLC layer having an amplitude greater than a threshold voltage for helix unwinding, and wherein the voltage source is further configured to apply electrical driving voltages to light emitting diodes (LEDs) of the FSC display to illuminate pixels of the FSC display. The pixels are illuminated in an FSC manner The FLC layer is configured to provide a defect-free layer of FLC under the electrical driving voltage applied to the FLC layer.

Claims

1. A field sequential color (FSC) ferroelectric liquid crystal (FSC) display cell, part of an FSC display, comprising:

two polarizers;

an FLC layer, positioned between the two polarizers, the FLC layer comprising FLCs with helix pitch less than the thickness of the FLC layer; and

a voltage source, configured to apply an electrical driving voltage to the FLC layer, the electrical driving voltage applied to the FLC layer having an amplitude greater than a threshold voltage for helix unwinding, and wherein the voltage source is further configured to apply electrical driving voltages to light emitting diodes (LEDs) of the FSC display to illuminate pixels of the FSC display, wherein the pixels are illuminated in an FSC manner;

wherein the FLC layer is configured to provide a defect-free layer of FLC under the electrical driving voltage applied to the FLC layer.

2. The display cell of claim 1, wherein the display cell is configured to provide electro-optical modulation with saturated bright and dark states, wherein the electrical driving voltage applied to the FLC layer has an applied voltage frequency of 5 kHz or less and an electric field amplitude of 5V/μ

m or less.

3. The display cell of claim 1, wherein the FLC layer is positioned between two substrates, and wherein the FLC layer further comprises smectic layers perpendicular to the substrates.

4. The display cell of claim 1, wherein the display cell is configured to provide a contrast ratio greater than or equal to approximately 10000:

1 when the electrical driving voltage applied to the FLC layer has a frequency of 5 kHz.

5. The display cell of claim 1, further comprising three subframes, each subframe corresponding to a color, wherein the display cell is configured to generate at least 8-bit gray levels in each subframe.

6. The display cell of claim 1, wherein the FSC display is configured to provide a viewing angle of at least approximately 80 degrees from a position normal to the FSC display, and wherein transmittance of the FSC display at 70°

from the normal position is at least approximately 60% of transmittance of the FSC display at the normal position.

7. The display cell of claim 1, wherein the display cell is configured to provide a range of colors corresponding to a color triangle greater than or equal to approximately 130% of a standard National Television System Committee (NTSC) color triangle with respect to a CIE 1931 color space when the electrical driving voltage applied to the FLC layer is less than or equal to approximately 3.5 volts/um.

8. The display cell of claim 1, wherein the voltage source comprises a matrix of thin film transistors (TFTs).

9. The display cell of claim 1, further comprising a pair of substrates covered with conducting layers, wherein the substrates comprise glass and/or plastic.

10. The display cell of claim 1, further comprising aligning layers, wherein the aligning layers include a photoalignment layer, a rubbed polyimide layer, and/or an alignment layer produced by oblique evaporation.

11. The display cell of claim 1, wherein an anchoring energy of an alignment layer of the display cell is less than an elastic energy of a helix of an FLC in the FLC layer.

12. The display cell of claim 1, wherein the two polarizers are crossed.

13. A field sequential color (FSC) ferroelectric liquid crystal (FSC) display cell, part of an FSC display, comprising:

a polarizer and a reflective layer;

an FLC layer, positioned between the polarizer and the reflective layer, the FLC layer comprising FLCs with helix pitch less than the thickness of the FLC layer; and

a voltage source, configured to apply an electrical driving voltage to the FLC layer, the electrical driving voltage applied to the FLC layer having an amplitude greater than a threshold voltage for helix unwinding, wherein the pixels are illuminated in an FSC manner by an external source; and

wherein the FLC layer is configured to provide a defect-free layer of FLC under the electrical driving voltage applied to the FLC layer.