Liquid crystal display including dopant phase-separated from liquid crystal

• US 6,151,096 A
• Filed: 12/02/1997
• Issued: 11/21/2000
• Est. Priority Date: 12/05/1996
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Gass, Paul Antony, Jones, John Clifford, Sakaigawa, Akira, Miyazaki, Aya, Sako, Teiyu, Towler, Michael John, Koden, Mitsuhiro, McDonnell, Damien Gerard
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US08/982,555
• Time in Patent Office: 1,085 Days
• Field of Search: 349/187, 349/188, 349/172, 349/85, 349/173
• US Class Current: 349/188
• CPC Class Codes: G02F 1/13775 Polymer-stabilized liquid crystal layers
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 2203/30 Gray scale

Abstract

A mixture of a ferroelectric or anti-ferroelectric liquid crystal material and a monomer having a single photopolymeric functional group is injected in the space between two electrode substrates while heat is applied. After cooling of the mixture it is irradiated with ultraviolet light at a temperature at which the liquid crystal material remains in the smectic phase so as to polymerise the monomer. Areas of liquid crystal material requiring different threshold voltages for switching are thereby produced. Alternatively such areas can be produced by changing the conditions applied to a mixture of liquid crystal material with a suitable dopant so as to cause separation of the dopant out of the liquid crystal material in order to provide a polarity of nucleation points for controlling domain formation within the liquid crystal material. Such control of domain formation can be used to provide greyscale in a liquid crystal device.

Claims

1. A method of manufacturing a liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) changing the conditions applied to the liquid crystal material so as to cause separation of the dopant out of the liquid crystal material which provides a plurality of anisotropic nucleation points for controlling domain formation within the liquid crystal material and keeping the liquid crystal material alignment.

2. A method according to claim 1, wherein said separation of the dopant out of the liquid crystal material is caused by the application of ultraviolet radiation to the liquid crystal material.

3. A method according to claim 1, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling switching of domains within the liquid crystal material between two or more stable states in operation of the device.

4. A method according to claim 1, for manufacture of a ferroelectric liquid crystal device, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling transitions between two alignment states of the liquid crystal device.

5. A method according to claim 1, for manufacture of a pi-cell device, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling nucleation of V state in the device.

6. A method according to claim 1, wherein two or more dopants are added to the liquid crystal material and separation of the dopants out of the liquid crystal material occurs under different conditions in order to provide a wide area between 0% and 100% switching curves.

7. A method according to claim 6, wherein said separation of one of the dopants is caused by the application of electromagnetic radiation, whereas said separation of another dopant is caused in some other manner.

8. A method of manufacturing a liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) changing the temperature of the liquid crystal material so as to cause separation of the dopant out of the liquid crystal material in order to provide a plurality of nucleation points for controlling domain formation within the liquid crystal material.

9. A method according to claim 8, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling switching of domains within the liquid crystal material between two or more stable states in operation of the device.

10. A method according to claim 8, for manufacture of a ferroelectric liquid crystal device, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling transitions between two alignment states of the liquid crystal device.

11. A method according to claim 8, for manufacture of a pi-cell device, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling nucleation of V state in the device.

12. A method of manufacturing a liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) changing the phase of the liquid crystal material so as to cause separation of the dopant out of the liquid crystal material in order to provide a plurality of nucleation points for controlling domain formation within the liquid crystal material.

13. A method according to claim 12, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling switching of domains within the liquid crystal material between two or more stable states in operation of the device.

14. A method according to claim 12, for manufacture of a ferroelectric liquid crystal device, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling transitions between two alignment states of the liquid crystal device.

15. A method according to claim 12, for manufacture of a pi-cell device, wherein said separation of the dopant out of the liquid crystal material provides a plurality of nucleation points for controlling nucleation of V state in the device.

16. A method of manufacturing a liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) changing the phase of the dopant so as to cause separation of the dopant out of the liquid crystal material in order to provide a plurality of nucleation points for controlling domain formation within the liquid crystal material.

17. A liquid crystal device including a cell comprising a layer of liquid crystal material contained between two substrates, the liquid crystal material incorporating a dopant which has been mixed with the liquid crystal material under predetermined applied conditions and which has been caused to separate out of the liquid crystal material due to a change in the applied conditions in order to provide a plurality of anisotropic nucleation points for controlling domain formation within the liquid crystal material and keeping the liquid crystal material alignment.

18. A method of manufacturing a liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) applying ultraviolet radiation to the liquid crystal material or the dopant so as to cause separation of the dopant out of the liquid crystal material in order to provide a plurality of nucleation points for controlling transitions between two alignment states of the liquid crystal device.

19. A method of manufacturing a pi-cell liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) applying ultraviolet radiation to the liquid crystal material or the dopant so as to cause separation of the dopant out of the liquid crystal material in order to provide a plurality of nucleation points for controlling nucleation of V states in the liquid crystal device.

20. A method of manufacturing a liquid crystal device which includes a cell comprising a layer of liquid crystal material contained between two substrates, the method comprising the steps of:

(a) adding to the liquid crystal material under predetermined applied conditions a dopant which is miscible with the liquid crystal material under said conditions; and

(b) changing the conditions applied to the liquid crystal material so as to cause separation of the dopant out of the liquid crystal material in order to provide a plurality of nucleation points for controlling domain formation within the liquid crystal material,

wherein two or more dopants are added to the liquid crystal material and separation of the dopants out of the liquid crystal material occurs under different conditions in order to provide a wide area between 0% and 100% switching curves.