Ferroelectric liquid crystal devices

• US 6,075,583 A
• Filed: 02/27/1997
• Issued: 06/13/2000
• Est. Priority Date: 08/31/1994
• Status: Expired due to Term

• Current Assignee: Xylon LLC (Intellectual Ventures LLC)
• Original Assignee: The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Jones, John Clifford, Bryan-Brown, Guy Peter, McDonnell, Damien Gerard, Mason, Ian Robert
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGO, HUYEN LE
• Application Number:
  US08/793,527
• Time in Patent Office: 1,202 Days
• Field of Search: 349/88, 349/184, 349/183, 349/33, 349/85, 349/127, 349/188
• US Class Current: 349/183
• CPC Class Codes: C09K 19/0225 Ferroelectric
• CPC Class Codes: C09K 19/542 Macromolecular compounds
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13775 Polymer-stabilized liquid crystal layers
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

In order to the effects of impact on liquid crystal devices a polymer network is introduced into ferroelectric liquid crystal cells. A liquid crystal device comprises two spaced cell walls each bearing electrode structures and treated on at least one facing surface with an alignment layer, a layer of a smectic liquid crystal material enclosed between the cell walls, characterised in that the liquid crystal material contains a small amount of monomer. The liquid crystal material may also contain a photoinitiator. The monomer material may be cured to produce the polymer network; the curing may be carried out in the presence of an electric or magnetic field. Further, the monomer may be cured in an isotropic or liquid crystal phase.

Claims

1. A liquid crystal device comprising:

two spaced cell walls, each cell wall bearing electrode structures and treated on at least one facing surface with an alignment layer; and

a layer of a smectic liquid crystal material enclosed between the cell walls wherein the liquid crystal material includes an amount of monomer which is subsequently at least partly polymerized into a polymer and said device exhibits a minimum in a response time verses voltage curve, wherein said amount of monomer lies in the range 0.01-2.0 wt. %.

2. A liquid crystal device according to claim 1 wherein the monomer is a liquid crystal monomer.

3. A liquid crystal device according to claim 1 wherein the polymer is prepared by the in-situ polymerization of said monomer.

4. A liquid crystal device according to claim 1 wherein the polymer is present as a network.

5. A method of reducing the susceptibility of ferroelectric liquid crystal cells to impact damage, said method comprising the steps of:

providing a liquid crystal device comprising two spaced cell walls, each wall bearing electrode structures and treated on at least one facing surface with an alignment layer;

providing a layer of a smectic liquid crystal material enclosed between the cell walls, wherein the liquid crystal material includes an amount of monomer which is subsequently at least partly polymerized into a polymer and said device exhibits a minimum in a response time verses voltage curve, wherein said amount of monomer lies in the range 0.01-2.0 wt. %.

6. A method according to claim 5 wherein the ferroelectric liquid crystal cell is surface stabilized.

7. A device according to claim 5 wherein the polymer is a liquid crystal polymer.

8. A method of reducing the susceptibility of ferroelectric liquid crystal cells to impact damage, said method comprising the steps of:

providing a liquid crystal device comprising two spaced cell walls, each wall bearing electrode structures and treated on at least one facing surface with an alignment layer;

providing a layer comprising an amount of polymer liquid crystal material and ferroelectric liquid crystal material, said layer enclosed between the cell walls wherein the polymer liquid crystal material is prepared by the in-situ polymerization of a monomer material and said device exhibits a minimum in a response time verses voltage curve, wherein said polymer is a cured monomer and the amount of monomer lies in the range 0.01-2.0 wt. %.