Method for controlling an index modulation of a switchable polymer dispersed liquid crystal optical component
View Patent ↗Described herein are the materials, mechanisms and procedures for optimizing various performance parameters of HPDLC optical devices in order to meet differing performance requirements. These optimization tailoring techniques include control and independent optimization of switchable HPDLC optical devices to meet the demanding requirements of anticipated applications for, inter alia, the telecommunications and display industries. These techniques include optimization of diffraction efficiency, i.e., index modulation, polarization dependence control, haze, cosmetic quality, control of response and relaxation time, voltage driving for on and off switching, and material uniformity. This control and independent optimization tailors properties of switchable HPDLC optical devices according to the specific requirements of the application of the switchable HPDLC optical device. The invention disclosed herein retains the desirable attributes of the multi-functional acrylate system for forming HPDLC optical devices, but adds new materials to the acrylate system and/or new process control to the recording to optimize performance parameters as may be needed for specific applications. This results in high optical quality switchable holograms with good diffraction efficiency and low, stable switching voltage.
1. A method for controlling an index modulation of a switchable polymer dispersed liquid crystal optical component comprising:
providing a pre-polymer liquid crystal material between a first and second substrate, the first and second substrate having a first and second electrode pattern thereon, respectively, for applying a switching voltage to the switchable polymer dispersed liquid crystal optical component, wherein at least one each of the first and second electrode patterns consists of interdigitated electrodes;
applying a voltage approximately equal to the switching voltage to only every other interdigitated electrode, creating an in-plane electric field within the pre-polymer liquid crystal material;
holographically irradiating the pre-polymer liquid crystal material resulting in polymerization of the pre-polymer liquid crystal, wherein liquid crystal droplets formed from the holographic irradiation are formed with symmetry axes oriented in a same direction as the in-plane electric field; and
removing the voltage approximately equal to the switching voltage once polymerization is complete.
2. The method according to claim 1 , wherein the interdigitated electrodes of the first electrode pattern are staggered with respect to the interdigitated electrodes of the second electrode pattern.
3. The method according to claim 1 , wherein at least one of the first and second electrode patterns is a solid planar pattern.
4. The method according to claim 1 , wherein each of the interdigitated electrodes has a height (h) and each of the interdigitated electrodes are separated by a separation (b), wherein each of (h) and (b) are approximately equal to the width of the polymer dispersed liquid crystal optical material.
5. The method according to claim 4 , wherein (h) is approximately 10 μm.
6. The method according to claim 4 , wherein (b) is approximately 10 μm.
7. The method according to claim 1 , wherein the first electrode pattern is transparent.
8. The method according to claim 1 , wherein a first fringing field of a first electrode superposes a second fringing field of a second electrode to create an in-plane electric field.
9. The method according to claim 8 , wherein the in-plane electric field orients a plurality of nematic directors in a plurality of forming droplets along the same in-plane direction as the electric field.
10. The method according to claim 9 , wherein the plurality of droplets are distorted in the direction of the electric field at equilibrium.
11. The method according to claim 10 , wherein the orientation of the nematic directors is established upon gelation and removal of the applied voltage.