Electro-optical device having a layer comprising an oblate liquid crystal dispersed in a resin and method for forming the same

• US 5,301,046 A
• Filed: 09/21/1992
• Issued: 04/05/1994
• Est. Priority Date: 09/21/1991
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Konuma, Toshimitsu, Hamatani, Toshiji, Yamazaki, Shunpei
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/947,456
• Time in Patent Office: 561 Days
• Field of Search: 359/51, 359/52
• US Class Current: 349/93
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals

Abstract

A liquid crystal electro-optical device based on a dispersion-type liquid crystal, comprising a pair of substrates at least one of which is light-transmitting, having established thereon electrodes and an electro-optical modulating layer having incorporated between said pair of substrates, said electro-optical modulating layer being composed of a resin support having dispersed therein a liquid crystal material, wherein, the liquid crystal material as viewed in the cross section is dispersed in the resin support as droplets flattened along the direction parallel to the substrates. The dispersion-type liquid crystal electro-optical device according to the present invention has a high scattering efficiency and provides an excellent light-transmittance upon application of an electric field.

Claims

1. An electro-optical device comprising:

a pair of substrates at least one of which is transparent, said substrates having at least patterned electrodes formed thereon; and

an electro-optical modulating layer provided between said substrates and comprising a resin and an oblate liquid crystal dispersed in said resin,

wherein said oblate liquid crystal is shaped by pressing said pair of substrates towards one another with said resin having said liquid crystal therein so that a length of said oblate liquid crystal in a direction parallel to said substrates is larger than that in a direction perpendicular to said substrates.

2. The device of claim 1 wherein a ratio of a length of said oblate liquid crystal in the direction parallel to said substrates to a length of said oblate liquid crystal in the direction perpendicular to said substrates is 1.2 to 5.0.

3. The device of claim 1 wherein said oblate liquid crystal comprises a liquid crystal selected from the group consisting of nematic liquid crystal, cholesteric liquid crystal and smectic liquid crystal.

4. The device of claim 3 wherein said electro-optical modulating layer comprises a dye.

5. The device of claim 1 wherein a refractive index of said oblate liquid crystal is different from that of said resin.

6. The device of claim 1 wherein said oblate liquid crystal has a minor axis of 1 to 4 μ

m.

7. A method for forming an electro-optical device comprising the steps of:

forming between a pair of substrates an electro-optical modulating layer comprising a resin and a liquid crystal dispersed in said resin; and

transforming said liquid crystal into an oblate shape by pressing said substrates toward one another.

8. The method of claim 7 wherein said liquid crystal comprises a liquid crystal selected from the group consisting of nematic liquid crystal, cholesteric liquid crystal and smectic liquid crystal.

9. The method of claim 8 wherein said electro-optical modulating layer comprises a dye.

10. The method of claim 7 wherein said substrates are pressed at a pressure of 1 to 5 kg/cm² during said transforming step.

11. The method of claim 7 wherein said liquid crystal is encapsulated.

12. The method of claim 11 wherein said resin comprises a polyvinyl alcohol encapsulating said liquid crystal.

13. The method of claim 7 wherein said electro-optical modulating layer forming step is carried out by applying a solution comprising said resin, said liquid crystal and a solvent to one of said substrates, subsequently volatilizing said solvent, and providing the other one of said substrates on said resin and said liquid crystal.

14. The method of claim 7 wherein said substrates are pressed at a temperature of 50°

to 150°

C. during said transforming step.

15. The method of claim 13 wherein the application of said solution is carried out by spinner method or cast method.

16. A method for forming an electro-optical device comprising the steps of:

forming between a pair of substrates an electro-optical modulating layer comprising an ultraviolet ray hardening resin and a liquid crystal;

irradiating said electro-optical modulating layer with an ultraviolet ray; and

transforming said liquid crystal into an oblate shape by pressing said substrates toward one another.

17. The method of claim 16 wherein said liquid crystal comprises a liquid crystal selected from the group consisting of nematic liquid crystal, cholesteric liquid crystal and smectic liquid crystal.

18. The method of claim 17 wherein said electro-optical modulating layer comprises a dye.

19. The method of claim 16 wherein said substrates are pressed at a pressure of 1 to 5 kg/cm² during said transforming step.

20. The method of claim 16 wherein said substrates are pressed at a temperature of 50°

to 150°

C. during said transforming step.

21. A method for forming an electro-optical device comprising the steps of:

forming an electro-optical modulating layer between a pair of substrates having at least patterned electrodes formed thereon, said electro-optical modulating layer comprising a resin and droplets of a liquid crystal dispersed in said resin; and

pressing said pair of substrates towards one another in order that the cross section of said droplets in a direction parallel to said substrates is increased.

22. The method of claim 21 wherein said substrates have TFTs for switching said electro-optical modulating layer.

23. A method for forming an electro-optical device comprising the steps of:

forming between a pair of substrates an electro-optical modulating layer comprising a resin and a liquid crystal dispersed in said resin; and

reducing the space between said pair of substrates.

24. The method of claim 23 wherein said reducing step is performed by pressing said pair of substrates toward one another after curing said resin.