Fast Switchable and High Diffraction Efficiency Grating Ferroelectric Liquid Crystal Cell

• US 20130169909A1
• Filed: 12/21/2012
• Published: 07/04/2013
• Est. Priority Date: 12/29/2011
• Status: Active Grant

• Current Assignee: Hong Kong University of Science and Technology
• Original Assignee: Hong Kong University of Science and Technology
• Inventors: Hu, Wei, Lu, Yanqing, Xu, Fei, Kwok, Hoi Sing, Srivastava, Abhishek Kumar, Chigrinov, Vladimir Grigorievich
• Granted Patent: US 9,575,366 B2
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133753 with different alignment orientations or pretilt angles on a same surface, e.g. for grey scale or improved viewing angle
• CPC Class Codes: G02F 1/133757 with different alignment orientations
• CPC Class Codes: G02F 1/133788 by light irradiation, e.g. linearly polarised light photo-polymerisation
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

A liquid crystal cell structure is provided. The liquid crystal cell structure includes: two polarizers; and a liquid crystal diffractive light modulating cell placed between the two polarizers. The cell includes: two transparent substrates treated by photoalignment; and a ferroelectric liquid crystal layer disposed between the two transparent substrates with current conducting layers, the ferroelectric liquid crystal layer comprising ferroelectric liquid crystals. The two transparent substrates treated by photoalignment are configured to provide multiple alignment domains in the ferroelectric liquid crystals with a planar surface orientation. Adjacent domains of the multiple alignment domains are oriented at an angle with respect to each other.

Claims

1. A liquid crystal cell structure, comprising:

two polarizers; and

a liquid crystal diffractive light modulating cell placed between the two polarizers, the cell comprising;

two transparent substrates treated by photoalignment; and

a ferroelectric liquid crystal layer disposed between the two transparent substrates with current conducting layers, the ferroelectric liquid crystal layer comprising ferroelectric liquid crystals;

wherein the two transparent substrates treated by photoalignment are configured to provide multiple alignment domains in the ferroelectric liquid crystals with a planar surface orientation; and

wherein adjacent domains of the multiple alignment domains are oriented at an angle with respect to each other.

2. The liquid crystal cell structure of claim 1, wherein the ferroelectric liquid crystals are electrically suppressed helix ferroelectric liquid crystals with helix pitch smaller than the thickness of the ferroelectric liquid crystal layer.

3. The liquid crystal cell structure of claim 1, wherein the ferroelectric liquid crystals are deformed helix ferroelectric liquid crystals.

4. The liquid crystal cell structure of claim 1, wherein the ferroelectric liquid crystals are surface stabilized ferroelectric liquid crystals.

5. The liquid crystal cell structure of claim 1, wherein the two transparent substrates treated by photoalignment comprise photoalignment material, the photoalignment material being sulfonic azo-dye SDI.

6. The liquid crystal cell structure of claim 1, wherein the two polarizers are crossed.

7. The liquid crystal cell structure of claim 2, wherein the liquid crystal diffractive light modulating cell has a response time less than 10 μ

s and a contrast of more than 4200;

1 at electric field less than 10 volts/μ

m.

8. The liquid crystal cell structure of claim 2, wherein the liquid crystal diffractive light modulating cell shows electro-optical modulation with saturated bright and dark states up to an applied voltage frequency of 5 kHz.

9. The liquid crystal cell structure of claim 1, wherein the first order diffraction efficiency of the cell structure is higher than 99%.

10. The liquid crystal cell structure of claim 1, where the alignment directions for two alignment domains are arranged at any angle greater than the tilt angle of the ferroelectric liquid crystals.

11. The liquid crystal cell structure of claim 1, wherein the ferroelectric liquid crystals have a pre-tilt angle on the surface to avoid the chevron defects.

12. The liquid crystal cell structure of claim 1, wherein the diffraction grating with said liquid crystal diffractive light modulating cell is of a transmission type.

13. The liquid crystal cell structure of claim 1, wherein the diffraction grating with said liquid crystal diffractive light modulating cell is of a reflective type.

14. A liquid crystal cell structure, comprising:

two polarizers; and

a liquid crystal diffractive light modulating cell placed between the two polarizers, the cell comprising;

two transparent substrates treated by photoalignment; and

an anti-ferroelectric liquid crystal layer disposed between the two transparent substrates with current conducting layers, the ferroelectric liquid crystal layer comprising ferroelectric liquid crystals;

wherein the two transparent substrates treated by photoalignment are configured to provide multiple alignment domains in the ferroelectric liquid crystals with a planar surface orientation; and

wherein adjacent domains of the multiple alignment domains are oriented at an angle with respect to each other.

15. A liquid crystal cell structure, comprising:

two polarizers; and

a liquid crystal diffractive light modulating cell placed between the two polarizers, the cell comprising;

two transparent substrates treated by photoalignment; and

a ferrielectric liquid crystal layer disposed between the two transparent substrates with current conducting layers, the ferroelectric liquid crystal layer comprising ferroelectric liquid crystals;

wherein the two transparent substrates treated by photoalignment are configured to provide multiple alignment domains in the ferroelectric liquid crystals with a planar surface orientation; and

wherein adjacent domains of the multiple alignment domains are oriented at an angle with respect to each other.