Biaxial liquid crystal electro-optic devices
An electro-optical device including a biaxial liquid crystal having a primary and secondary director is provided. A change in orientation of at least one of the directors due to an applied electric field produces a change in the optical state of the device. Response times are increased dramatically over uniaxial nematic based liquid crystal devices, offering improved performance and efficiency.
1. An electro-optical device comprising first and second substrates, each of said first and second substrates coated with an alignment layer, and a liquid crystal material positioned between said substrates, said liquid crystal material comprising a biaxial nematic liquid crystal having a first principal director n and a secondary director m, wherein a change in the optical properties of said device are effected by reorienting at least one of said m and n.
2. An electro-optical device according to claim 1 , wherein said biaxial nematic liquid crystal comprises a bent-core liquid crystal.
3. An electro-optical device according to claim 2 , wherein said bent-core liquid crystal comprises at least one of
where R 1 and R 2 independently comprise a straight chain alkyl or substituted alkyl having from 5 to 20 carbon atoms.
4. An electro-optical device according to claim 3 , wherein R 1 comprises —OC 8 H 17 and R 2 comprises —C 12 H 25 .
5. An electro-optical device according to claim 1 , further comprising first and second polarizers, wherein said polarizers are at right angles to each other.
6. An electro-optical device according to claim 1 , wherein said biaxial nematic liquid crystal comprises at least one of
7. An electro-optical device according to claim 1 , wherein n lies along the average long axis of the liquid crystal.
8. An electro-optical device according to claim 1 , wherein m is perpendicular to n.
9. An electro-optical device according to claim 1 , further comprising a voltage source for applying an electric field between said first and second substrates.
10. An electro-optical device according to claim 9 , wherein n and m are parallel to said substrates at zero applied voltage.
11. An electro-optical device according to claim 10 , wherein at least one of n and m reorients perpendicularly to said substrates at a specified applied voltage.
12. An electro-optical device according to claim 1 , wherein said device is capable of switching between first and second optical states at least twice as fast as a uniaxial nematic liquid crystal based electro-optical device.
13. A biaxial retardation film comprising first and second transparent electrodes, and a liquid crystal material positioned between said electrodes, said liquid crystal material comprising a biaxial nematic liquid crystal having a first principal director n and a secondary director m, wherein n and m are perpendicular to each other and parallel to said electrodes at an applied electric field of zero.
14. A biaxial retardation film according to claim 13 , wherein at least one of said n and m directors can be reoriented by the application of an electric field.
15. A biaxial retardation film according to claim 13 , wherein both n and m can be reoriented independently by the application of an electric field using different tunable frequencies.
16. A biaxial retardation film according to claim 13 , wherein said biaxial nematic liquid crystal comprises a bent-core liquid crystal.
17. A biaxial retardation film according to claim 16 , wherein said bent-core liquid crystal comprises at least one of
where R 1 and R 2 independently comprise a straight chain alkyl or substituted alkyl having from 5 to 20 carbon atoms.
18. A biaxial retardation film according to claim 13 , wherein R 1 comprises —OC 8 H 17 and R 2 comprises —C 12 H 25 .
19. A biaxial retardation film according to claim 13 , wherein said biaxial liquid crystal comprises at least one of
20. A method of forming an electro-optical device comprising depositing a liquid crystal material between first and second substrates, each of said first and second substrates coated with an alignment layer, said liquid crystal material comprising a biaxial nematic liquid crystal having a first principal director n and a secondary director m, wherein a change in the optical properties of said device are effected by reorienting at least one of said m and n.
21. The electro-optical device according to claim 1 , wherein both n and m can be reoriented independently by the application of an electric field using different tunable frequencies.
22. The method according to claim 20 , wherein both n and m can be reoriented independently by the application of an electric field using different tunable frequencies.