Non-lithographic photo-induced patterning of polymers from liquid crystal solvents with spatially modulated director fields

• US 6,897,915 B1
• Filed: 09/27/2001
• Issued: 05/24/2005
• Est. Priority Date: 09/27/2000
• Status: Expired due to Fees

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Shiyanovskii, Sergij, Lavrentovich, Oleg D., Voloschenko, Dmitry
• Primary Examiner(s): Flynn, Nathan J.
• Assistant Examiner(s): Sefer, Ahmed N.
• Application Number:
  US09/966,294
• Time in Patent Office: 1,335 Days
• Field of Search: 349/88, 349/84, 349/115, 349/123
• US Class Current: 349/88
• CPC Class Codes: G02F 1/133377 Cells with plural compartments or having plurality of liquid crystal microcells partitioned by walls, e.g. one microcell per pixel
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 2201/305 diffraction grating

Abstract

A liquid crystal device comprises a first and second cell wall structure; at least one liquid crystal material disposed within a space between the first and second cell wall structures; and polymer micro-structures, wherein the micro-structures are formed by polymerizing a prepolymer, and wherein said micro-structures have a shape and spatial location determined by said liquid crystal material. Permanent polymer micro-structures are formed from a liquid crystal with a non-uniform spatially modulated director field. The polymer structures have the shape and spatial location dictated by the non-uniform director field of the liquid crystal. The micro-structures are a backbone that restores the liquid crystal director field that existed during the polymerization process even when other factors, such as electric field, temperature, or surface anchoring, do not favor this restoration. The polymer micro-structures can be used in optical devices, such as diffraction gratings and deflecting and beam steering devices, and in micro-mechanical and micro-fluidic devices.

Claims

1. A method for fabricating a liquid crystal device having polymer micro-structures, the method comprising the steps of:

preparing a mixture comprising a liquid crystal material and a prepolymer;

providing a first and second cell wall structure, said first and second cell wall structures optionally having electrodes disposed on facing sides of said first and second cell wall structures, and, optionally having an alignment layer disposed on at least one of said electrodes;

disposing said mixture into a space between the first and second cell wall structures;

causing said liquid crystal material to assume a predetermined orientation with a non-uniform spatially distorted director field; and

exposing said mixture to conditions which cause polymerization of the prepolymer and formation of polymer micro-structures between the cell walls, wherein the micro-structures have a shape and spatial location determined by a director field of said liquid crystal material.

2. A method for fabricating a liquid crystal device having polymer micro-structures according to claim 1, wherein said mixture comprising a liquid crystal material and a prepolymer comprises between about 0.1 percent and about 50 percent prepolymer.

3. A method for fabricating a liquid crystal device having polymer micro-structures according to claim 1, wherein said liquid crystal material is selected from the group consisting of cholesteric liquid crystal material, nematic liquid crystal material, columnar liquid crystal material and smectic liquid crystal material.

4. A method for fabricating a liquid crystal device having polymer micro-structures according to claim 1, wherein said prepolymer is selected from the group consisting of UV-curable prepolymers and heat-curable prepolymers.

5. A method for fabricating a liquid crystal device having polymer micro-structures according to claim 1, wherein said first and second cell wall structures have electrodes disposed thereon, and wherein said step of causing said liquid crystal material to assume a predetermined orientation with a non-uniform spatially distorted director field comprises applying a voltage across said electrodes.

6. A method for forming polymer micro-structures, the method comprising the steps of:

preparing a mixture comprising a liquid crystal material and a prepolymer;

providing a first and second cell wall structure;

disposing said mixture into a space between the first and second cell wall structures;

causing said liquid crystal material to assume a predetermined orientation with a non-uniform spatially distorted director field; and

exposing said mixture to conditions which cause polymerization of the prepolymer and formation of polymer micro-structures between the cell walls, wherein the micro-structures have a shape and spatial location determined by a director field of said liquid crystal material.

7. The method for forming polymer micro-structures according to claim 6, wherein the prepolymer is a UV-curable prepolymer and wherein the step of exposing the mixture to conditions which cause polymerization of the prepolymer comprises exposing the prepolymer to UV radiation.

8. The method for forming polymer micro-structures according to claim 6, wherein the first and second cell wall structures additionally comprise electrodes disposed on facing sides of said first and second cell wall structures.

9. The method for forming polymer micro-structures according to claim 6, wherein at least one of said first and second cell wall structures additionally comprise an alignment layer disposed thereon.

10. The method for forming polymer micro-structures according to claim 6, wherein said mixture comprising a liquid crystal material and a curable prepolymer comprises between about 0.1 percent and about 50 percent curable prepolymer.

11. The method for forming polymer micro-structures according to claim 6, wherein said liquid crystal material is selected from the group consisting of nematic liquid crystal material, cholesteric liquid crystal material, columnar liquid crystal material and smectic liquid crystal material.

12. A method for forming a liquid crystal cell comprising the method for forming polymer micro-structures according to claim 6.

13. A liquid crystal cell formed by the method of claim 6.