Pressure sensitive liquid crystalline light modulating device and material

• US 6,104,448 A
• Filed: 12/15/1999
• Issued: 08/15/2000
• Est. Priority Date: 05/02/1991
• Status: Expired due to Fees

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Chien, Liang-Chy, Doane, J. William, Yang, Deng-Ke
• Primary Examiner(s): Dudek, James A.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US09/465,192
• Time in Patent Office: 244 Days
• Field of Search: 349/12, 349/169, 349/20, 349/25, 349/23, 349/86, 349/176, 349/115, 349/158
• US Class Current: 349/12
• CPC Class Codes: C09K 19/02 characterised by optical, electrical or physical properties of the components, in general
• CPC Class Codes: C09K 19/542 Macromolecular compounds
• CPC Class Codes: C09K 19/586 Optically active dopants; chiral dopants
• CPC Class Codes: G02F 1/0131 based on photo-elastic effects, e.g. mechanically induced birefringence
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G02F 1/13775 Polymer-stabilized liquid crystal layers

Abstract

A new liquid crystalline light modulating cell and material are characterized by liquid crystalline light modulating material of liquid crystal and polymer, the liquid crystal being a chiral nematic liquid crystal having positive dielectric anisotropy and including chiral material in an amount effective to form focal conic and twisted planar textures, the polymer being distributed in phase separated domains in the liquid crystal cell in an amount that permits the liquid crystal to change textures upon the application of a field and ruggedizes the structure. In still another embodiment, the material exhibits stability at zero field in a colored, light reflecting state, a light scattering state and multiple stable reflecting state therebetween, as well as being optically clear in the presence of a field. In yet another embodiment, the application of mechanical force to the cell changes the material from an optically clear state to a light reflecting state.

Claims

1. A light modulating cell, comprising

liquid crystalline light modulating material of liquid crystal and polymer, the liquid crystal being a chiral nematic liquid crystal having positive dielectric anisotropy and including chiral material in an amount effective to form a light scattering focal conic texture and a light reflecting planar texture having a pitch length that reflects light in the visible spectrum, the polymer being distributed in phase separated domains in the cell in an amount that stabilizes the thickness and structure of the cell, wherein the application of a mechanical stress to the liquid crystalline light modulating material changes an initial light scattering focal conic texture to the light reflecting planar texture.

2. The cell according to claim 1, wherein the application of an electric field to the cell returns the planar texture to the initial texture.

3. The cell according to claim 1, wherein the chiral nematic liquid crystal contains from about 27 to about 66% chiral material based on the combined weight of nematic liquid crystal and chiral material.

4. The cell according to claim 1, wherein the polymer is present in an amount of from about 1.5 to about 40% based on the total weight of polymer and liquid crystal in the cell.