Guest-host mode liquid crystal display device of lateral electric field driving type

• US 6,697,129 B1
• Filed: 03/29/1999
• Issued: 02/24/2004
• Est. Priority Date: 02/14/1996
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hirakata, Yoshiharu, Nishi, Takeshi, Satake, Rumo
• Primary Examiner(s): Ngo, Julie
• Application Number:
  US09/280,185
• Time in Patent Office: 1,793 Days
• Field of Search: 349/33, 349/42, 349/141, 349/179
• US Class Current: 349/33
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/13725 based on guest-host interaction G02F1/13762, G02F1/13737, take precedence
• CPC Class Codes: G02F 1/1397 the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells

Abstract

A liquid crystal display device comprising a light modulating layer being interposed between a first substrate and a second substrate, a common electrode being formed over the first substrate in parallel with a drain electrode, wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate, wherein said light modulating layer comprising a liquid crystal material, an optically active substance and a dichroic dye is operated in a guest-host mode, wherein said liquid crystal material has a spiral pitch p in a range of 1<p<15 μm, and wherein a cell thickness d is in a range of 1<d<10 μm.

Claims

1. A liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a light modulating layer being interposed between the first substrate and the second substrate;

at least a pixel being formed over the first substrate, said pixel comprising;

a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a drain electrode being connected to the drain region;

a gate line being connected to the gate electrode;

a common electrode being formed in parallel with the drain electrode;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer is operated in a guest-host mode,

wherein said liquid crystal display device includes no polarizing plate,

wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye,

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m, and

wherein a cell thickness d is in a range of 1≦

d≦

10 μ

m.

2. A device according to claim 1, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

3. A device according to claim 1, wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

4. A device according to claim 1, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.

5. A liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a light modulating layer being interposed between the first substrate and the second substrate, said light modulating layer including at least a liquid crystal material;

at least a pixel being formed over the first substrate, said pixel comprising;

a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a drain electrode being connected to the drain region;

a gate line being connected to the gate electrode;

a common electrode being formed in parallel with the drain electrode;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer is operated in a guest-host mode,

wherein said liquid crystal display device includes no polarizing plate,

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m,

wherein a cell thickness d is in a range of 1≦

d≦

10 μ

m,

wherein molecules of said liquid crystal material have an orientation twist angle θ

in a range of θ

≦

300°

,

wherein an interelectrode distance L being defined between said drain electrode and said common electrode is in a range of L≦

25 μ

m.

6. A device according to claim 5, wherein said light modulating layer further includes an optically active substance and a dichroic dye.

7. A device according to claim 5, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

8. A device according to claim 5, wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

9. A device according to claim 5, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.

10. A reflective type liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a reflection plate formed over one of said substrates;

a light modulating layer being interposed between the first substrate and the second substrate;

at least a pixel being formed over the first substrate, said pixel comprising;

a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a drain electrode being connected to the drain region;

a gate line being connected to the gate electrode;

a common electrode being formed in parallel with the drain electrode;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer is operated in a guest-host mode,

wherein said liquid crystal display device includes no polarizing plate,

wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye,

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m, and

wherein a cell thickness d is in a range of 1≦

d≦

10 μ

m.

11. A device according to claim 10, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

12. A device according to claim 10, wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

13. A device according to claim 10, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.

14. A liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a light modulating layer being interposed between the first substrate and the second substrate;

at least a pixel being formed over the first substrate, said pixel comprising;

a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a drain electrode being connected to the drain region;

a gate line being connected to the gate electrode;

a common electrode being formed in parallel with the drain electrode;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer is operated in a guest-host mode,

wherein said liquid crystal display device includes no polarizing plate,

wherein a light shielding means is formed over at least one of the first and second substrates to shield at least said channel region, and

wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye,

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m, and

wherein a cell thickness d is in a range of 1≦

d≦

10 μ

m.

15. A device according to claim 14, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

16. A device according to claim 14, wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

17. A device according to claim 14, wherein said light shielding means comprises one selected from a metal and a polymeric material with a black pigment therein.

18. A device according to claim 14, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.

19. A liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a light modulating layer being interposed between the first substrate and the second substrate;

at least a pixel being formed over the first substrate, said pixel comprising;

a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a drain electrode being connected to the drain region;

a gate line being connected to the gate electrode;

a common electrode being formed in parallel with the drain electrode;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer has first and second states, said first state being capable of transmitting a light while said second state being capable of absorbing the light,

wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye, and

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m.

20. A device according to claim 19, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

21. A device according to claim 19, wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

22. A device according to claim 19, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.

23. A liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a light modulating layer being interposed between the first substrate and the second substrate;

at least a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a drain electrode being connected to the drain region;

a gate line being connected to the gate electrode;

an insulating film comprising an organic resin and being formed over the thin film transistor and the drain electrode;

a common electrode being formed in parallel with the drain electrode and being formed over the insulating film;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye, and

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m.

24. A device according to claim 23, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

25. A device according to claim 23, wherein the thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

26. A device according to claim 23, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.

27. A liquid crystal display device comprising:

a first substrate;

a second substrate opposing to the first substrate;

a light modulating layer being interposed between the first substrate and the second substrate;

at least a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;

a gate line being connected to the gate electrode;

a first interlayer insulating film being formed over at least the gate electrode;

a drain electrode being connected to the drain region and being formed over the first interlayer insulating film;

a second interlayer insulating film comprising an organic resin and being formed over the first interlayer insulating film and the drain electrode;

a common electrode being formed In parallel with the drain electrode and being formed over the second interlayer insulating film;

a common line being connected to the common electrode,

wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,

wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye, and

wherein said liquid crystal material has a spiral pitch p in a range of 1≦

p≦

15 μ

m.

28. A device according to claim 27, wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island.

29. A device according to claim 27, wherein the thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type.

30. A device according to claim 27, wherein said liquid crystal material shows a cholesteric phase with no application of voltage.