Standing helix ferroelectric liquid crystal display cell

• US 10,451,948 B2
• Filed: 01/20/2016
• Issued: 10/22/2019
• Est. Priority Date: 01/20/2015
• Status: Active Grant

• Current Assignee: Hong Kong University of Science and Technology
• Original Assignee: Hong Kong University of Science and Technology
• Inventors: Pozhidaev, Evgenii P., Kiselev, Alexei D., Srivastava, Abhishek K., Chigrinov, Vladimir G., Kwok, Hoi Sing
• Primary Examiner(s): Crockett, Ryan
• Application Number:
  US15/544,995
• Publication Number:
  US 20180017833A1
• Time in Patent Office: 1,371 Days
• Field of Search: None
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/133742 for homeotropic alignment
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 1/1418 using smectic liquid crystals, e.g. based on the electroclinic effect
• CPC Class Codes: G02F 2201/124 interdigital
• CPC Class Codes: G02F 2203/06 Polarisation independent

Abstract

A standing helix ferroelectric liquid crystal display cell includes: two transparent substrates (102A, 102B); a ferroelectric liquid crystal layer (104) comprising ferroelectric liquid crystals in a standing helix configuration, the ferroelectric liquid crystal layer (104) being disposed between the two transparent substrates (102A, 102B), the ferroelectric liquid crystals having a helix axis perpendicular to the two substrates (102A, 102B) and chiral smectic liquid crystal helix pitch shorter than a wavelength of a polarized light normally impinging at least one of the two transparent substrates (102A, 102B); and inter-digital electrodes (105), disposed in plane with the two transparent substrates (102A, 102B), configured to apply an electric field to the ferroelectric liquid crystal layer (104) that provides a driving voltage below a critical voltage for helix unwinding.

Claims

1. A standing helix ferroelectric liquid crystal display cell, comprising:

two transparent substrates;

a ferroelectric liquid crystal layer comprising ferroelectric liquid crystals in a vertically-aligned standing helix configuration, the ferroelectric liquid crystal layer being disposed between the two transparent substrates, the ferroelectric liquid crystals having a helix axis perpendicular to the two transparent substrates and chiral smectic liquid crystal helix pitch shorter than a wavelength of polarized light normally impinging on at least one of the two transparent substrates;

inter-digital electrodes, disposed in plane with the two transparent substrates, configured to apply an electric field to the ferroelectric liquid crystal layer that provides a driving voltage below a critical voltage for helix unwinding; and

an alignment layer disposed on at least one of the two transparent substrates, configured to provide the vertical alignment for the ferroelectric liquid crystals.

2. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the two transparent substrates comprise glass or plastic.

3. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the inter-digital electrodes comprise patterned transparent conductive layers.

4. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the alignment layer comprises stearic acid chromium salt dissolved in a solvent.

5. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the driving voltage is provided using active or passive addressing.

6. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the ferroelectric liquid crystals have an equilibrium state characterized by an undistorted helix while the driving voltage is not applied, wherein the equilibrium state is configured to be polarization independent to light propagating along the helix axis.

7. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein application of the driving voltage provides continuous modulation of light that is hysteresis free and insensitive to the driving voltage polarity.

8. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the ferroelectric liquid crystal layer is configured, based on the helix pitch, to avoid effects of polarization plane rotation, diffraction and scattering on light passing along the helix axis.

9. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein at least one of the inter-digital electrodes is configured to apply an electric field parallel to the two transparent substrates.

10. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein frequency of the driving voltage is within a range from 10 Hz to 5 kHz.

11. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the ferroelectric liquid crystal display cell is configured to provide a transmissive mode.

12. The standing helix ferroelectric liquid crystal display cell according to claim 1, wherein the ferroelectric liquid crystal display cell is configured to provide a reflective mode.

13. A field sequential color display, comprising a standing helix ferroelectric liquid crystal display cell, the standing helix ferroelectric liquid crystal display cell comprising:

two transparent substrates;

a ferroelectric liquid crystal layer comprising ferroelectric liquid crystals in a vertically-aligned standing helix configuration, the ferroelectric liquid crystal layer being disposed between the two transparent substrates, the ferroelectric liquid crystals having a helix axis perpendicular to the two transparent substrates and chiral smectic liquid crystal helix pitch shorter than a wavelength of polarized light normally impinging on at least one of the two transparent substrates;

inter-digital electrodes, disposed in plane with the two transparent substrates, configured to apply an electric field to the ferroelectric liquid crystal layer that provides a driving voltage below a critical voltage for helix unwinding; and

an alignment layer disposed on at least one of the two transparent substrates, configured to provide the vertical alignment for the ferroelectric liquid crystals;

wherein the field sequential color display is configured to generate a color image by integration of images in fast switching distinct color fields.

14. The field sequential color display according to claim 13, comprising:

at least three distinct color fields.

15. The field sequential color display according to claim 13, wherein the field sequential color display is configured to generate optical gray scale based on analog addressing for the distinct color fields.

16. The field sequential color display according to claim 13, wherein the field sequential color display is configured to generate optical gray scale based on digital addressing for the distinct color fields.