Method of producing a homogeneously aligned chiral smectic C liquid crystal having homeotropic alignment layers

• US 5,315,419 A
• Filed: 07/23/1992
• Issued: 05/24/1994
• Est. Priority Date: 05/19/1992
• Status: Expired due to Fees

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Jakli, Antal, Saupe, Alfred
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TRICE, RONALD
• Application Number:
  US07/918,918
• Time in Patent Office: 670 Days
• Field of Search: 359/46, 359/56, 359/77, 359/78, 359/100
• US Class Current: 349/131
• CPC Class Codes: G02F 1/133719 with coupling agent molecules, e.g. silane
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

A method for promoting uniform "bookshelf" textures in light modulators using smectic C* liquid crystal is disclosed. The method comprises the steps of confining smectic C* phase liquid crystal between parallel substrates having inner surfaces treated to promote homeotropic alignment of the liquid crystal near the inner surfaces, generating an electric field normal to the inner surfaces of the substrates and biasing the liquid crystal in a direction parallel to the inner surfaces of the substrates to induce the formation of smectic layers normal to the inner surfaces of the substrate. For example, the perturbation may be carried out by supplying a cyclic shear to one of the substrates or by means of a magnetic field parallel to the substrates. Reversal of the polarity of the electric field switches the material between two stable bookshelf textures. These textures are homogeneous in alignment even near the inner surfaces of the substrates, and the anchoring of the molecules near the substrates changes as the material is switched between bookshelf textures.

Claims

1. A method for producing a ferroelectric liquid crystal film comprising the steps of:

a) confining smectic C* phase liquid crystal between parallel substrates having inner surfaces treated to promote homeotropic alignment of the liquid crystal near the inner surfaces;

b) generating an electric field in the liquid crystal normal to the inner surfaces of the substrates; and

c) biasing the liquid crystal in a direction parallel to the inner surfaces of the substrates to induce a realignment of the liquid crystal molecules into homogeneously aligned layers with boundaries perpendicular to the inner surfaces of the substrates.

2. A method according to claim 1 wherein the inner surfaces of the substrates are defined by a layer of silane material which promotes homeotropic alignment of the liquid crystal near the inner surfaces.

3. A method according to claim 1 wherein the substrates support transparent electrodes bounding the liquid crystal and the step of generating an electric field in the liquid crystal includes coupling electric signals to the transparent electrodes.

4. A method according to claim 1 wherein the step of biasing the liquid crystal includes supplying a cyclic shear to one of the substrates.

5. A method according to claim 1 wherein the step of generating an electric field in the liquid crystal includes generating a DC field, and wherein the step of biasing the liquid crystal includes generating a magnetic field in the liquid crystal parallel to the inner surfaces of the substrates.

6. A method according to claim 1 wherein the step of biasing the liquid crystal is accomplished by propagating a transition front.

7. A method according to claim 6 wherein the propagated front is produced by increasing an electric field that has a gradient parallel to an inner surface of the material.

8. A method according to claim 6 wherein the propagated front is produced by moving a step in an electric field across the film.