Field sequential color ferroelectric liquid crystal display cell

Patent metadata

Field	Value
Publication number	US-9366934-B2
Application number	US-201314070149-A
Country	US
Kind code	B2
Filing date	Nov 1, 2013
Priority date	Nov 1, 2012
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

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.

First claim

The invention claimed is:

1. A ferroelectric liquid crystal (FLC) display cell, 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;
a first electrode, positioned on one side of the FLC layer;
a second electrode, positioned on an opposing side of the FLC layer; and
a voltage source, configured to apply a driving voltage so as to generate an electric field in a direction perpendicular to the plane of the FLC layer via the first and second electrodes, wherein the driving voltage is applied via a pulse width modulation driving scheme, and wherein an amplitude of the driving voltage is greater than a threshold voltage for helix unwinding;
wherein the FLC layer is configured to provide a defect-free layer of FLC and to generate gray scales by being switched between a bright state and a dark state under application of the driving voltage via the pulse width modulation driving scheme;
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.

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 driving voltage corresponds to an applied voltage frequency of 5 kHz or less and an electric field amplitude of 5V/μm 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 , 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.

5. The display cell of claim 1 , wherein the display cell is configured to provide a viewing angle of at least approximately 80 degrees from a position normal to the display cell, and wherein transmittance of the display cell at 70° from the normal position is at least approximately 60% of transmittance of the display cell at the normal position.

6. 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/μm.

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

8. The display cell of claim 1 , further comprising:
a pair of substrates, wherein the substrates comprise glass and/or plastic, and wherein the first and second electrodes comprise respective conducting layers on the respective substrates.

9. 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.

10. 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.

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

12. A ferroelectric liquid crystal (FLC) display cell, 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;
a first electrode, positioned on one side of the FLC layer;
a second electrode, positioned on an opposing side of the FLC layer; and
a voltage source, configured to apply a driving voltage so as to generate an electric field in a direction perpendicular to the plane of the FLC layer via the first and second electrodes, wherein the driving voltage is applied via a pulse width modulation driving scheme, and wherein an amplitude of the driving voltage is greater than a threshold voltage for helix unwinding;
wherein the FLC layer is configured to provide a defect-free layer of FLC and to generate gray scales by being switched between a bright state and a dark state under application of the driving voltage via the pulse width modulation driving scheme;
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.

Assignees

• Univ Hong Kong Science & Techn

Inventors

• Srivastava Abhishek Kumar
• Ma Ying
• Chigrinov Vladimir Grigorievich
• Kwok Hoi Sing

Classifications

• G02F1/13306

  Circuit arrangements or driving methods for the control of single liquid crystal cells (G02F1/132, G02F1/133382 take precedence) · CPC title

• G02F1/141 Primary

  using ferroelectric liquid crystals · CPC title

• G09G2310/0235

  Field-sequential colour display · CPC title

• G09G2300/0404

  Matrix technologies · CPC title

• G09G3/36

  using liquid crystals · CPC title