Liquid crystal display device with improved field angles

• US 20040008309A1
• Filed: 03/24/2003
• Published: 01/15/2004
• Est. Priority Date: 03/13/1998
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Inoue, Iichiro, Yamahara, Motohiro
• Granted Patent: US 7,009,678 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133632 with refractive index ellipsoid inclined relative to the LC-layer surface
• CPC Class Codes: G02F 1/1396 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell G02F1/141 takes precedence
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation

Abstract

The liquid crystal display device of this invention includes: a liquid crystal display element including a pair of substrates, a liquid crystal layer interposed between the pair of substrates, and an alignment film formed on a surface of at least one of the pair of substrates facing the liquid crystal layer; a pair of polarizers disposed on both surfaces of the liquid crystal element to sandwich the liquid crystal element; and at least one optical phase element disposed between at least one of the pair of polarizers and the liquid crystal element, wherein three principal refractive indices na, nb, and nc of an index ellipsoid of the optical phase element have the relationship of na=nc>nb, a direction of the principal refractive index nb is tilted clockwise or counterclockwise from the normal of a surface of the optical phase element with respect to a direction of one of the principal refractive indices na and no which is substantially parallel to the surface of the optical phase element as an axis, and a direction of the other principal refractive index no or na is tilted clockwise or counterclockwise from a direction substantially parallel to the surface of the optical phase element, and at least one of rates of variation of an ordinary refractive index no and an extraordinary refractive index ne of a liquid crystal material of the liquid crystal layer with respect to a wavelength is set in a range in which viewing angle dependent coloring does not occur on a screen.

Claims

1. A liquid crystal display device comprising:

a liquid crystal display element including a pair of substrates, a liquid crystal layer interposed between the pair of substrates, and an alignment film formed on a surface of at least one of the pair of substrates facing the liquid crystal layer;

a pair of polarizers disposed on both surfaces of the liquid crystal element to sandwich the liquid crystal element; and

at least one optical phase element disposed between at least one of the pair of polarizers and the liquid crystal element,

wherein three principal refractive indices na, nb, and no of an index ellipsoid of the optical phase element have the relationship of na=nc>

nb, a direction of the principal refractive index nb is tilted clockwise or counterclockwise from the normal of a surface of the optical phase element with respect to a direction of one of the principal refractive indices na and no which is substantially parallel to the surface of the optical phase element as an axis, and a direction of the other principal refractive index no or na is tilted clockwise or counterclockwise from a direction substantially parallel to the surface of the optical phase element, and

at least one of rates of variation of an ordinary refractive index no and an extraordinary refractive index ne of a liquid crystal material of the liquid crystal layer with respect to a wavelength is set in a range in which viewing angle dependent coloring does not occur on a screen.

3. A liquid crystal display device according to claim 1, further comprising a plurality of pixel regions for displaying, wherein at least one of the plurality of pixel regions is divided into a first liquid crystal molecule orientation domain and a second liquid crystal molecule orientation domain which have different orientation states of liquid crystal molecules included in the liquid crystal layer, and the area of the first liquid crystal molecule orientation domain is larger than the area of the second liquid crystal molecule orientation domain.

5. A liquid crystal display device according to claim 1, wherein the rate of variation among extraordinary light refractive indices ne(450), ne(550), and ne(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, have the relationship of:

6. A liquid crystal display device according to claim 1, wherein the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.65≦

(no(450)−

no(550))/(no(550)−

no(650))≦

2.40.

7. A liquid crystal display device according to claim 6, wherein the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.85≦

(no(450)−

no(550))/(no(550)−

no(650))≦

2.20.

8. A liquid crystal display device according to claim 1, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.70≦

(ne(450)−

ne(550))/(ne(550)−

ne(650))≦

2.30.

9. A liquid crystal display device according to claim 8, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.85≦

(ne(450)−

ne(550))/(ne(550)−

ne(650))23 2.10.

10. A liquid crystal display device according to claim 1, wherein the rate of variation among extraordinary light refractive indices ne(450), ne(550), and ne(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, have the relationship of:

11. A liquid crystal display device according to claim 1, wherein the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.00≦

(no(450)−

no(550)) (no(550)−

no(650)) ≦

1.65.

12. A liquid crystal display device according to claim 11, wherein the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.15≦

(no(450)−

no(550))/(no(550)−

no(650))≦

1.45.

13. A liquid crystal display device according to claim 1, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.20≦

(ne(450)−

ne(550))/(ne(550)−

ne(650))≦

1.70.

14. A liquid crystal display device according to claim 13, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, is set in a range of:

1.35≦

(ne(450)−

ne(550))/(ne(550)−

ne(650))≦

1.60.

21. A liquid crystal display device according to claim 1, wherein a value of refractive index anisotropy Δ

n(550) of the liquid crystal material for light with a wavelength of 550 nm is set in a range of;

0.060<

Δ

n(550)<

0.120.

23. A liquid crystal display device according to claim 21, wherein the value of the refractive index anisotropy Δ

n(550) of the liquid crystal material for light with a wavelength of 550 nm is set in a range of;

0.070<

Δ

n(550)<

0.095.

25. A liquid crystal display device according to claim 1, wherein a tilt angle of the index ellipsoid of the optical phase element is set in a range between 15°

and 75°

inclusive.

27. A liquid crystal display device according to claim 1, wherein the product of the difference between the principal refractive indices na and nb of the optical phase element and the thickness d of the optical phase element, i.e., (na−

nb)×

d is set in a range between 80 nm and 250 nm inclusive.

29. A liquid crystal display device according to claim 3, wherein the liquid crystal display element and the optical phase element are arranged so that an alignment direction of the alignment film is opposite to a tilt direction of the principal refractive indices nb and no of the optical phase element in the first liquid crystal molecule orientation domain.

31. A liquid crystal display device according to claim 29, wherein the liquid crystal display element and the optical phase element are arranged so that the alignment direction of the alignment film is the same as the tilt direction of the principal refractive indices nb and no of the optical phase element in the second liquid crystal molecule orientation domain.

33. A liquid crystal display device according to claim 3, wherein an area ratio of the first liquid crystal molecule orientation domain to the second liquid crystal molecule orientation domain in the at least one pixel region is set in a range between 6:

4 and 19;

1 inclusive.

35. A liquid crystal display device according to claim 1, wherein liquid crystal molecules in the liquid crystal layer are twisted about 90°

between the pair of substrates.

2. A liquid crystal display device comprising:

a liquid crystal display element including a pair of substrates, a liquid crystal layer interposed between the pair of substrates, and an alignment film formed on a surface of at least one of the pair of substrates facing the liquid crystal layer;

a pair of polarizers disposed on both surfaces of the liquid crystal element to sandwich the liquid crystal element; and

at least one optical phase element disposed between at least one of the pair of polarizers and the liquid crystal element,

wherein three principal refractive indices na, nb, and nc of an index ellipsoid of the optical phase element have the relationship of na=nc>

nb, a direction of the principal refractive index nb is tilted clockwise or counterclockwise from the normal of a surface of the optical phase element with respect to a direction of one of the principal refractive indices na and no which is substantially parallel to the surface of the optical phase element as an axis, and a direction of the other principal refractive index nc or na is tilted clockwise or counterclockwise from a direction substantially parallel to the surface of the optical phase element, and conditions of the combination of a length of a mean alkyl chain of a liquid crystal material of the liquid crystal layer, a rate of variation of an ordinary refractive index no of the liquid crystal material with respect to a wavelength, and a rate of variation of an extraordinary refractive index ne of the liquid crystal material with respect to a wavelength are set in a range in which viewing angle dependent coloring does not occur on a screen.

4. A liquid crystal display device according to claim 2, further comprising a plurality of pixel regions for displaying, wherein at least one of the plurality of pixel regions is divided into a first liquid crystal molecule orientation domain and a second liquid crystal molecule orientation domain which have different orientation states of liquid crystal molecules included in the liquid crystal layer, and the area of the first liquid crystal molecule orientation domain is larger than the area of the second liquid crystal molecule orientation domain.

15. A liquid crystal display device according to claim 2, wherein the length m of the mean alkyl chain (C_mH_2m+1) of the liquid crystal material is set in a range of m<

3.40, and the rate of variation among extraordinary light refractive indices ne(450), ne(550), and ne(650) of the liquid crystal material for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are set in a range of;

16. A liquid crystal display device according to claim 15, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) of the liquid crystal material for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are set in a range of:

17. A liquid crystal display device according to claim 2, wherein the length m of the mean alkyl chain (C_mH_2m+—

) of the liquid crystal material is set in a range of 3.40≦

m≦

3.90, and the rate of variation among extraordinary light refractive indices ne(450), ne(550), and ne(650) of the liquid crystal material for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are set in a range of;

18. A liquid crystal display device according to claim 17, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) of the liquid crystal material for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are set in a range of:

19. A liquid crystal display device according to claim 2, wherein the length m of the mean alkyl chain (C_mH_2m+1—

) of the liquid crystal material is set in a range of m>

3.90, and the rate of variation among extraordinary light refractive indices ne(450), ne(550), and ne(650) of the liquid crystal material for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are set in a range of;

20. A liquid crystal display device according to claim 19, wherein the rate of variation among the extraordinary light refractive indices ne(450), ne(550), and ne(650) of the liquid crystal material for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the rate of variation among the ordinary light refractive indices no(450), no(550), and no(650) for light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are set in a range of:

22. A liquid crystal display device according to claim 2, wherein a value of refractive index anisotropy Δ

n(550) of the liquid crystal material for light with a wavelength of 550 nm is set in a range of;

0.060<

Δ

n(550)<

0.120.

24. A liquid crystal display device according to claim 22, wherein the value of the refractive index anisotropy Δ

n(550) of the liquid crystal material for light with a wavelength of 550 nm is set in a range of;

0.070<

Δ

n(550)<

0.095.

26. A liquid crystal display device according to claim 2, wherein a tilt angle of the index ellipsoid of the optical phase element is set in a range between 15°

and 75°

inclusive.

28. A liquid crystal display device according to claim 2, wherein the product of the difference between the principal refractive indices na and nb of the optical phase element and the thickness d of the optical phase element, i.e., (na−

nb)×

d is set in a range between 80 nm and 250 nm inclusive.

30. A liquid crystal display device according to claim 4, wherein the liquid crystal display element and the optical phase element are arranged so that an alignment direction of the alignment film is opposite to a tilt direction of the principal refractive indices nb and no of the optical phase element in the first liquid crystal molecule orientation domain.

32. A liquid crystal display device according to claim 30, wherein the liquid crystal display element and the optical phase element are arranged so that the alignment direction of the alignment film is the same as the tilt direction of the principal refractive indices nb and no of the optical phase element in the second liquid crystal molecule orientation domain.

34. A liquid crystal display device according to claim 4, wherein an area ratio of the first liquid crystal molecule orientation domain to the second liquid crystal molecule orientation domain in the at least one pixel region is set in a range between 6:

4 and 19;

1 inclusive.

36. A liquid crystal display device according to claim 2, wherein liquid crystal molecules in the liquid crystal layer are twisted about 90°

between the pair of substrates.