Dual frequency cholesteric display and drive scheme
AssigneeKent State University
InventorsDeng-Ke Yang, Ming Xu
Life of this patent
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Abstract
A dual frequency cholesteric display includes a pair of opposed substrates, wherein one of the substrates has a first plurality of electrodes facing a second plurality of electrodes on the other substrate. A dual frequency bistable cholesteric liquid crystal material is disposed between the substrates, wherein the material and the intersection of the first and second plurality of electrodes forms a plurality of pixels. By selectively applying high and low frequency voltages to the plurality of pixels, the high frequency voltage causes the material to exhibit one texture and the low frequency voltage causes the material to exhibit another texture. By adjusting a voltage amplitude value for each high and low frequency causes each pixel to exhibit a desired reflectance.
Claims22
A method of addressing a dual frequency bistable cholesteric liquid crystal material having liquid crystal domains disposed between opposed substrates, wherein one of the substrates has a first plurality of electrodes facing a second plurality of electrodes on the other substrate, and wherein the intersection of the first and the second plurality of electrodes forms a plurality of pixels, the method comprising the steps of:
- selectively applying high and low frequency voltages to said plurality of pixels, wherein the high frequency voltage drives the material to exhibit one texture so that the liquid crystal domains have a reflectance at one extreme and the low frequency voltage drives the material to exhibit another texture so that the liquid crystal domains have a reflectance at another extreme, wherein the liquid crystal domains are stable after removal of the voltages;
- adjusting a voltage amplitude value for each said high and low frequency to obtain a desired reflectance which can be at either extreme or somewhere between the two extremes, wherein said desired reflectance is made up of pixels, each said pixel having a first portion of liquid crystal domains at one extreme and another portion of liquid crystal domains at the other extreme;
- and
- cumulatively adjusting the desired reflectance by simultaneously applying said high and low frequency voltages in multiple pulses such that switching of the liquid crystal domains is accomplished cumulatively so that the amplitude or the duration of the pulses, or both can be reduced.
A dual frequency cholesteric display, comprising:
- a pair of opposed substrates, wherein one of said substrates has a first plurality of electrodes facing a second plurality of electrodes on the other substrate;
- a reflective dual frequency bistable cholesteric liquid crystal material disposed between said substrates, wherein the material and the intersection of the first and second plurality of electrodes forms a plurality of pixels, said material having liquid crystal domains, wherein a plurality of said liquid crystal domains are contained in each of said pixels such that all the liquid crystal domains in a pixel can be either in a focal conic or a planar texture, or the liquid crystal domains in a pixel can have any combination of focal conic and planar textures;
- means for selectively applying high and low frequency voltages to said plurality of pixels, wherein the high frequency voltage drives the material to exhibit predominantly one texture and the low frequency voltage drives the material to exhibit predominantly another texture;
- means for adjusting a voltage amplitude value for each said high and low frequency to obtain a desired reflectance for each pixel, wherein adjusting the voltage amplitude drives the liquid crystal domains in a corresponding manner so as to change the proportion of liquid crystal domains in each texture;
- and
- means for cumulatively adjusting the reflectance by simultaneously applying high and low frequency voltage pulses to both said plurality of electrodes, wherein cumulatively switching of the liquid crystal domains between textures is accomplished by multiple pulses so that the amplitude or the duration of the pulses, or both can be reduced.
A method of addressing a dual frequency bistable cholesteric liquid crystal material having liquid crystal domains disposed between opposed substrates, wherein one of the substrates has a first plurality of electrodes facing a second plurality of electrodes on the other substrate, and wherein the intersection of the first and the second plurality of electrodes forms a plurality of pixels, the method comprising the steps of:
- selectively applying high and low frequency voltages to said plurality of pixels, wherein the high frequency voltage drives the material to exhibit one texture so that the liquid crystal domains have a reflectance at one extreme and the low frequency voltage drives the material to exhibit another texture so that the liquid crystal domains have a reflectance at another extreme, wherein the liquid crystal domains are stable after removal of the voltages;
- and
- adjusting a voltage amplitude value for each said high and low frequency to obtain a desired reflectance which can be at either extreme or somewhere between the two extremes, wherein said desired reflectance is made up of pixels, each said pixel having a first portion of liquid crystal domains at one extreme and another portion of liquid crystal domains at the other extreme.
A dual frequency cholesteric display, comprising:
- a pair of opposed substrates, wherein one of said substrates has a first plurality of electrodes facing a second plurality of electrodes on the other substrate;
- a reflective dual frequency bistable cholesteric liquid crystal material disposed between said substrates, wherein the material and the intersection of the first and second plurality of electrodes forms a plurality of pixels, said material having liquid crystal domains, wherein a plurality of said liquid crystal domains are contained in each of said pixels such that all the liquid crystal domains in a pixel can be either in a focal conic or a planar texture, or the liquid crystal domains in a pixel can have any combination of focal conic and planar textures;
- means for selectively applying high and low frequency voltages to said plurality of pixels, wherein the high frequency voltage drives the material to exhibit predominantly one texture and the low frequency voltage drives the material to exhibit predominantly another texture;
- and
- means for adjusting a voltage amplitude value for each said high and low frequency to obtain a desired reflectance for each pixel, wherein adjusting the voltage amplitude drives the liquid crystal domains in a corresponding manner so as to change the proportion of liquid crystal domains in each texture.
Dependencies are inferred from the claim text.