Liquid crystal device and method thereof
The invention provides a liquid crystal device and method thereof. Subsequent to applying a first electrical voltage on a liquid crystal to induce a reorientation of the liquid crystal, a second electrical voltage with proper polarity is applied on the liquid crystal to assist the relaxation of the reorientation that was induced by the first electrical voltage. The “switch-off” phase of the liquid crystal can therefore be accelerated or temporally shortened, and the device can exhibit better performance such as fast response to on/off signals. The invention can be widely used LCD, LC shutter, LC lens, spatial light modulator, telecommunication device, tunable filter, beam steering device, and electrically driven LC device, among others.
1. A method for accelerating the reorientation of the liquid crystal in a liquid crystal cell comprising:
(1) applying a first electrical voltage on the liquid crystal to polarize the liquid crystal in an “ON” state and induce a memory polarization of the liquid crystal, the first electrical voltage being applied from a first electrical voltage generator,
(2) removing the first electrical voltage to induce a time of dielectric relaxation of the liquid crystal from the reorientation induced by the first electrical voltage, and
(3) applying a second electrical voltage on the polarized liquid crystal to assist the relaxation, the second electrical voltage being applied from a second electrical voltage generator, wherein the second electrical voltage is applied during the time of dielectric relaxation of the liquid crystal and acts on the memory polarization to accelerate reorientation of the liquid crystal to an “OFF” state.
2. The method according to claim 1 , in which the liquid crystal is dielectrically dispersive.
3. The method according to claim 1 , in which the liquid crystal comprises a nematic liquid crystal.
4. The method according to claim 1 , in which the liquid crystal cell is selected from homeotropic cell, planar cell, and high pretilt cell.
5. The method according to claim 1 , in which the first electrical voltage is a pulse.
6. The method according to claim 1 , in which the liquid crystal has a negative dielectric anisotropy Δ∈, and the polarity of the first electrical voltage and the polarity of the second electrical voltage are the same.
7. The method according to claim 1 , in which the liquid crystal has a positive dielectric anisotropy Δ∈, and the polarity of the first electrical voltage and the polarity of the second electrical voltage are opposite.
8. The method according to claim 1 , in which the time span between the step of removing the first electrical voltage and the step of applying the second electrical voltage is substantially zero.
9. The method according to claim 1 , in which the liquid crystal is a nematic liquid crystal with negative dielectric anisotropy Δ∈.
10. The method according to claim 9 , in which the liquid crystal comprises a mixture of MLC-7026-100 and 2F-3333.
11. The method according to claim 1 , in which the liquid crystal is a nematic liquid crystal with positive dielectric anisotropy Δ∈.
12. The method according to claim 11 , in which the liquid crystal comprises a mixture of 5CB and 2F-3333.
13. The method according to claim 1 , in which the step of removing the first electrical voltage and starting of the application of the second electrical voltage is accomplished with the back edge of the first electrical voltage pulse.
14. The method according to claim 13 , in which the back edge is an instantaneous back edge or an exponentially decaying back edge.
15. A liquid crystal device comprising:
a liquid crystal cell, a first electrical voltage generator, and a second electrical voltage generator, wherein said first electrical voltage generator generates a first electrical voltage which applies on the liquid crystal to polarize the liquid crystal in an “ON” state and induce a memory polarization of the liquid crystal; and
said second electrical voltage generator generates a second electrical voltage which applies on the liquid crystal during a time of dielectric relaxation of the liquid crystal induced by removal of the first voltage and accelerates reorientation of the liquid crystal from the “ON” state induced by the first electrical voltage to an “OFF” state.
16. The device according to claim 15 , in which the liquid crystal comprises a nematic liquid crystal.
17. The device according to claim 15 , in which the liquid crystal has a negative dielectric anisotropy Δ∈, and the polarity of the first electrical voltage and the polarity of the second electrical voltage are the same.
18. The device according to claim 15 , in which the liquid crystal has a positive dielectric anisotropy Δ∈, and the polarity of the first electrical voltage and the polarity of the second electrical voltage are opposite.
19. The device according to claim 15 , in which the first electrical voltage generator and the second electrical voltage generator are merged into one single device selected from a pulse generator, a function generator, and a wave-form generator.
20. The device according to claim 15 , which is selected from LCD, LC shutter, LC lens, spatial light modulator, telecommunication device, tunable filter, beam steering device, and electrically driven LC device.