Stressed liquid crystals as an ultra-fast light modulating material consisting of unidirectionally oriented liquid crystal micro-domains separated by polymer chains
A new light modulating material using unidirectionally oriented micro-domains of liquid crystal separated by polymer chains is provided. Liquid crystal/polymer films are produced by a one step production process involving a photopolymerizable monomer mixed with a liquid crystal then exposed to UV light. In one embodiment, force deformations are applied to the films resulting in diffraction efficiencies of more than 95%. In another embodiment, applying a planar force to a thick film that produced a 2 μm shift of phase retardation in several hundred microseconds when an appropriate field is applied. Use of this invention provides fast response time and a low required driving voltage. The new cell can be used as spatial light modulators for manufacturing information displays, electro-optical devices, telecommunications system, optical data processing, adaptive optics applications, color projection displays and switchable micro-lens optics.
1. A light modulating cell, comprising:
at least two spaced apart substrates;
at least one electrode provided with each substrate to apply an electrical field therebetween another;
a light modulating material disposed between said substrates, said light modulating material comprising
a larger proportion of liquid crystal material; and
a smaller proportion of polymeric material that forms domains interspersed in said larger proportion of liquid crystal material, to form interconnected liquid crystal areas, wherein the liquid crystal material is substantially uniformly aligned in an initial state in the interconnected liquid crystal areas; and
a power supply connected to said electrodes to selectively apply an electric field to said liquid crystal material to selectively re-orient at least some of said liquid crystal areas to generate a predetermined phase shift of any light impinging the cell.
2. The cell according to claim 1 , wherein application of said electric field causes at least an amount of said liquid crystal material to exhibit a homeotropic texture.
3. The cell according to claim 1 , wherein said polymer material comprises about 10% weight to about 22% weight of said light modulating material.
4. The cell according to claim 1 , wherein no specialized surface treatments are applied to said electrodes.
5. The cell according to claim 1 , wherein an amount of said phase shift depends at least upon a magnitude of said electric field.
6. The cell according to claim 1 , wherein initial alignment of the liquid crystal material is produced by application of a force to the material, and the amount of said phase shift depends at least upon an amount of displacement of said liquid crystal directors with respect to said substrates obtained by applying the force to the light modulating material.
7. The cell according to claim 6 , wherein substantially all of said liquid crystal areas are oriented along the direction of the force.
8. The cell according to claim 1 , wherein said substrates are selected to be transparent or reflective.
9. The cell according to claim 1 , wherein the light modulating material is substantially transparent.
10. The cell according to claim 1 , wherein light modulating material is substantially homogenous.
11. The cell according to claim 1 , wherein the light modulating material produces phase retardation of light impinging thereon, with the amount of phase retardation controllable by the applied voltage from said electrodes.
12. The cell according to claim 1 , wherein in the light modulating material is capable of producing a phase shift of up to about 3.75 μm in less than 1.0 millisecond.
13. The cell according to claim 12 , wherein the light modulating material does not substantially scatter visible light.
14. The cell according to claim 1 , wherein upon the application of an electric field to generate the phase shift, the transmittance properties of the material remain substantially the same.
15. The cell according to claim 1 , wherein the transmittance properties of the light modulating material do not substantially vary based on the polarization of light impinging thereon.
16. The cell according to claim 1 , wherein the phase retardation of the light modulating material is substantially linear.
17. The cell according to claim 1 , wherein the light modulating material is formed into a film, and the thickness of the film can be varied to alter the phase shift characteristics thereof.