Liquid crystal display apparatus

• US 6,493,053 B1
• Filed: 08/04/2000
• Issued: 12/10/2002
• Est. Priority Date: 08/06/1999
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nakata, Morio, Shiomi, Makoto, Miyachi, Koichi, Yamahara, Motohiro
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGO, HUYEN LE
• Application Number:
  US09/632,878
• Time in Patent Office: 858 Days
• Field of Search: 349/117, 349/119
• 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 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
• CPC Class Codes: G02F 1/133738 for homogeneous alignment
• 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

Abstract

A liquid crystal display apparatus of the present invention includes: a liquid crystal display device, the liquid crystal display device including: a pair of light transmissive substrates; a transparent electrode layer and an alignment film which are provided on one surface of each of the light transmissive substrates, the surface facing the other one of the light transmissive substrates; and a liquid crystal layer interposed between the pair of light transmissive substrates, wherein: the liquid crystal layer includes liquid crystal molecules; the liquid crystal molecules on a surface on each of the alignment films are pre-tilted in the same direction and by the same angle as those on a surface of the other one of the alignment films; and the liquid crystal layer has a homogeneous orientation; a pair of polarizers provided on respective sides of the liquid crystal display device; and at least one inclined phase plate including an index ellipsoid having three principal refractive indices na, nb and nc, wherein: the three principal refractive indices na, nb and nc of the index ellipsoid satisfy a relationship of na=nb>nc; each of the principal refractive indices na and nb is a principal refractive index along a direction in a surface of the inclined phase plate, and the principal refractive index nc is a principal refractive index along a direction normal to the surface of the inclined phase plate; the index ellipsoid is inclined by inclining the direction of the principal refractive index nc and the direction of one of the in-plane principal refractive indices na and nb with respect to each other about an axis extending along the direction of the other one of the in-plane principal refractive indices na and nb; the inclined phase plate is provided between the liquid crystal display device and at least one of the polarizers; and the inclined phase plate is arranged so that an inclination direction of the index ellipsoid as being projected onto the surface of one of the light transmissive substrates is generally parallel or antiparallel to an orientation direction of the liquid crystal molecules.

Claims

1. A liquid crystal display apparatus, comprising:

a liquid crystal display device, the liquid crystal display device comprising;

a pair of light transmissive substrates;

a transparent electrode layer and an alignment film which are provided on one surface of each of the light transmissive substrates, the surface facing the other one of the light transmissive substrates; and

a liquid crystal layer interposed between the pair of light transmissive substrates, wherein;

the liquid crystal layer includes liquid crystal molecules;

the liquid crystal molecules on a surface of each of the alignment films are pre-tilted in the same direction and by the same angle as those on a surface of the other one of the alignment films; and

the liquid crystal layer has a homogeneous orientation;

a pair of polarizers provided on respective sides of the liquid crystal display device; and

at least one inclined phase plate including an index ellipsoid having three principal refractive indices na, nb and nc, wherein;

the three principal refractive indices na, nb and nc of the index ellipsoid satisfy a relationship of na=nb>

nc;

each of the principal refractive indices na and nb is a principal refractive index along a direction in a surface of the inclined phase plate, and the principal refractive index nc is a principal refractive index along a direction normal to the surface of the inclined phase plate;

the index ellipsoid is inclined by inclining the direction of the principal refractive index nc and the direction of one of the in-plane principal refractive indices na and nb with respect to each other about an axis extending along the direction of the other one of the in-plane principal refractive indices na and nb;

the inclined phase plate is provided between the liquid crystal display device and at least one of the polarizers; and

the inclined phase plate is arranged so that an inclination direction of the index ellipsoid as being projected onto the surface of one of the light transmissive substrates is generally parallel or antiparallel to an orientation direction of the liquid crystal molecules.

2. A liquid crystal display apparatus according to claim 1, wherein:

the liquid crystal display apparatus further comprises at least one negative phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz along an x axis, a y axis and a z axis, respectively;

the three principal refractive indices nx, ny and nz satisfy a relationship of nx=ny>

nz;

the x axis and the y axis extend in the surface of the negative phase plate and the z axis extends in a direction normal to the surface of the negative phase plate; and

the negative phase plate is provided between the liquid crystal display device and at least one of the polarizes.

3. A liquid crystal display apparatus according to claim 2, wherein:

where the negative phase plate is provided on both sides of the liquid crystal display device, a product (nx−

nz)×

d of a difference between the principal refractive index nx and the principal refractive index nz and a thickness d of the negative inclined phase plate is set to be in a range from 5 nm to 200 nm; and

where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

nz)×

d is set to be in a range from 10 nm to 400 nm.

4. A liquid crystal display apparatus according to claim 3, wherein:

where the negative phase plate is provided on both sides of the liquid crystal display device, a product (nx−

nz)×

d is set to be in a range from 35 nm to 105nm; and

where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

nz)×

d is set to be in a range from 70 nm to 210 nm.

5. A liquid crystal display apparatus according to claim 1, wherein:

the liquid crystal display apparatus further comprises at least one positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively;

the principal refractive indices nx, and ny satisfy a relationship of nx>

ny;

the x axis and the y axis extend in the surface of the positive phase plate;

the negative phase plate is provided between the liquid crystal display device and at least one of the polarizers;

each of the polarizers has an absorption axis; and

the positive phase plate is arranged so that the y axis substantially coincides with the absorption axis.

6. A liquid crystal display apparatus according to claim 5, wherein:

where the positive phase plate is provided on both sides of the liquid crystal display device, a product (nx−

nz)×

d of a difference between the principal refractive index nx and the principal refractive index ny and a thickness d of the positive inclined phase plate is set to be in a range from 1 nm to 1.25 nm; and

where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

ny)×

d is set to be in a range from 2 nm to 250 nm.

7. A liquid crystal display apparatus according to claim 6, wherein:

where the positive phase plate is provided on both sides of the liquid crystal display device, a product (nx−

nz)×

d is set to be in a range from 30 nm to 90 nm; and

where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

ny)×

d is set to be in a range from 60 nm to 180 nm.

8. A liquid crystal display apparatus according to claim 1, wherein:

the liquid crystal display apparatus further comprises at least one negative phase plate including a negative index ellipsoid having three principal refractive indices nx1, ny1 and nz1 along an x1 axis, a y1 axis and a z1 axis, respectively;

the three principal refractive indices nx1, ny1 and nz1 satisfy a relationship of nx1=ny1>

nz1;

the x1 axis and the y1 axis extend in the surface of the negative phase plate and the z1 axis extends in a direction normal to the surface of the negative phase plate;

the negative phase plate is provided between the liquid crystal display device and at least one of the polarizers;

the liquid crystal display apparatus further comprises at least one positive phase plate including a positive index ellipsoid having three principal refractive indices nx2, ny2 and nz2 along an x2 axis, a y2 axis and a z2 axis, respectively;

the principal refractive indices nx2 and ny2 satisfy a relationship of nx2>

ny2;

the x2 axis and the y2 axis extend in the surface of the positive phase plate;

the positive phase plate is provided between the liquid crystal display device and at least one of the polarizers;

each of the polarizers has an absorption axis; and

the positive phase plate is arranged so that the y2 axis substantially coincides with the absorption axis.

9. a liquid crystal display apparatus according to claim 1, wherein the inclined phase plate is arranged so that the inclination direction of the index ellipsoid and a pre-tilt direction of the liquid crystal molecules are substantially opposite to each other.

10. A liquid crystal display apparatus according to claim 1, wherein an inclination angle of the index ellipsoid is equal to or greater than 10°

and less than or equal to 80°

.

11. A liquid crystal display apparatus according to claim 10, wherein the inclination angle of the index ellipsoid is equal to or greater than 20°

and less than or equal to 50°

.

12. A liquid crystal display apparatus according to claim 1, wherein:

where the inclined phase plate is provided on both sides of the liquid crystal display device, a product (na−

nc)×

d of a difference between the principal refractive index na and the principal refractive index nc and thickness d of the inclined phase plate is set to be in a range from 15 nm to 700 nm; and

where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (na−

nc)×

d is set to be in a range from 30 nm to 1500 nm.

13. A liquid crystal display apparatus according to claim 12, wherein:

where the inclined phase plate is provided on both sides of the liquid crystal display device, the product (na−

nc)×

d is set to be in a range from 33 nm to 159 nm; and

where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (na−

nc)×

d is set to be in a range from 66 nm to 318 nm.

14. A liquid crystal display apparatus according to claim 1, wherein:

each of the polarizers has an absorption axis; and

an angle between a direction of the absorption axis and an inclination direction of the index ellipsoid in the inclined phase plate is greater than −

5° and

less than 50°

.

15. A liquid crystal display apparatus according to claim 1, wherein an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is greater than −

5° and

less than 5°

.

16. A liquid crystal display apparatus according to claim 1, wherein an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate 0°

.

17. A liquid crystal display apparatus according to claim 1, wherein the inclined phase plate includes a support made of a transparent organic polymer and a discotic liquid crystal material cured on the support in an inclined orientation.

18. A liquid crystal display apparatus according to claim 1, wherein the inclined phase plate includes a support made of a transparent organic polymer and a discotic liquid crystal material cured on the support in an hybrid orientation.

19. A liquid crystal display apparatus according to claim 1, wherein a product of a thickness of the liquid crystal layer and a refractive index anisotropy (Δ

n) of the liquid crystal layer is in a range from 180 nm to 500 nm.

20. A liquid crystal display apparatus according to claim 19, wherein a product of a thickness of the liquid crystal layer and the refractive index anisotropy (Δ

n) of the liquid crystal layer is in a range from 220 nm to 350 nm.

21. A liquid crystal display apparatus according to claim 1, further comprising an element for diffusing transmitted light in normal and near-normal viewing directions toward upper and lower directions.

22. A liquid crystal display apparatus according to claim 1, wherein:

the liquid crystal display apparatus further comprises at least one positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively;

the principal refractive indices nx and ny satisfy a relationship of nx>

ny;

the x axis and the y axis exist in a surface of the positive phase plate;

the positive phase plate is provided between the inclined phase plate and the liquid crystal display device;

each of the polarizers has an absorption axis;

the x axis, which is a slow axis of the positive phase plate, is substantially parallel or substantially orthogonal to an inclination direction of the index ellipsoid of the inclined phase plate as being projected onto the surface of one of the light transmissive substrates; and

an angle between the absorption axis of each of the polarizers and the slow axis of the positive phase plate is substantially 45°

.

23. A liquid crystal display apparatus according to claim 22, wherein a difference between (1) a sum of an in-plane retardation of the negative inclined phase plate and an in-plane retardation of the positive inclined phase plate and (2) a retardation of the liquid crystal layer when a black display is produced by the liquid crystal display apparatus is within ±

10 nm.

24. A liquid crystal display apparatus according to claim 23, wherein the sum of the in-plane retardation of the negative inclined phase plate and the in-plane retardation of the positive inclined phase plate is less than or equal to 100 nm.

25. A liquid crystal display apparatus according to claim 1, wherein:

the liquid crystal display apparatus further comprises a positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively;

the principal refractive indices nx and ny satisfy a relationship of nx>

ny;

the x axis and the y axis exist in a surface of the positive phase plate;

the positive phase plate is provided between the inclined phase plate and at least one of the polarizers;

each of the polarizers has an absorption axis;

the x axis, which is a slow axis of the positive phase plate, is substantially parallel or substantially orthogonal to an inclination direction of the index ellipsoid of the inclined phase plate as being projected onto the surface of one of the light transmissive substrates; and

an angle between the absorption axis of each of the polarizers and the slow axis of the positive phase plate is substantially 45°

.

26. A liquid crystal display apparatus, comprising:

a liquid crystal display device, the liquid crystal display device comprising;

a pair of light transmissive substrates;

a transparent electrode layer and an alignment film which are provided on one surface of each of the light transmissive substrates, the surface facing the other one of the light transmissive substrates; and

a liquid crystal layer interposed between the pair of light transmissive substrates, wherein;

the liquid crystal layer includes liquid crystal molecule;

the liquid crystal molecules on a surface of each of the alignment films are pre-tilted in the same direction and by the same angle as those on a surface of the other one of the alignment films;

the liquid crystal layer has a homogeneous orientation;

a pair of polarizers provided on respective sides of the liquid crystal display device; and

at least one inclined phase plate including an index ellipsoid having three principal refractive indices, na, nb and nc, wherein;

the three principal refractive indices na, nb and nc of the index ellipsoid satisfy a relationship of na=nb>

nc;

each of the principal refractive indices na and nb is a principal refractive index along a direction in a surface of the inclined phase plate, and the principal refractive index nc is a principal refractive index along a direction normal to the surface of the inclined phase plate;

the index ellipsoid is inclined by inclining the direction of the principal refractive index nc and the direction of one of the in-plane principal refractive indices na and nb with respect to each other about an axis extending along the direction of the other one of the in-plane principal refractive indices na and nb;

the inclined phase plate is provided between the liquid crystal display device and at least one of the polarizers;

the liquid crystal display apparatus further comprises at least one positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively;

the principal refractive indices nx and ny satisfy a relationship of nx>

ny;

the x axis and the y axis extend in the surface of the positive phase plate;

the positive phase plate is provided between the liquid crystal display device and at least one of the polarizers;

each of the polarizers has an absorption axis;

the positive phase plate is arranged so that the y axis substantially coincides with an orientation direction of the liquid crystal molecules; and

the inclined phase plate is arranged so that an inclination direction of the index ellipsoid as being projected onto the surface of one of the light transmissive substrates is generally parallel or antiparallel to an orientation direction of the liquid crystal molecules.

27. A liquid crystal display apparatus according to claims 26, wherein;

a liquid crystal display apparatus further comprises at least one negative phase plate including a negative index ellipsoid having three principal refractive indices nx1, ny1 and nz1 along an x1 axis, a y1 axis and a z1 axis, respectively;

the three principal refractive indices nx1, ny1 and nz1 satisfy a relationship of nx1=ny1>

nz1;

the x1 axis and the y1 axis extend in the surface of the negative phase plate and the z1 axis extends in a direction normal to the surface of the negative phase plate; and

the negative phase plate is provided between the liquid crystal display device and at least one of the polarizers.

28. A liquid crystal display apparatus according to claim 27, wherein:

where the negative phase plate is provided on both sides of the liquid crystal display device, a product (nx−

nz)×

d of a difference between the principal refractive index nx and the principal refractive index nz and a thickness d of the negative inclined phase plate is set to be in a range from 1 nm to 100 nm; and

where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

nz)×

d is set to be in a range from 2 nm to 200 nm.

29. A liquid crystal display apparatus according to claim 28, wherein:

where the negative phase plate is provided on both sides of the liquid crystal display device, a product (nx−

nz)×

d is set to be in a range from 1 nm to 30 nm; and

where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

nz)×

d is set to be in a range from 2 nm to 60 nm.

30. A liquid crystal display apparatus according to claim 26, wherein:

where the inclined phase plate is provided on both sides of the liquid crystal display device, a product (na−

nc)×

d of a difference between the principal refractive index na and the principal refractive index nc and a thickness d of the inclined phase plate is set to be in a range from 1 nm to 200 nm; and

where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (na−

nc)×

d is set to be in a range from 2 nm to 400 nm.

31. A liquid crystal display apparatus according to claim 30, wherein:

where the inclined phase plate is provided on both sides of the liquid crystal display device, the product (na−

nc)×

d is set to be in a range from 30 nm to 150 nm; and

where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (na−

nc)×

d is set to be in a range from 60 nm to 300 nm.

32. A liquid crystal display apparatus according to claim 26, wherein an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is greater than 40°

and less than 50°

.

33. A liquid crystal display apparatus according to claim 26, wherein an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is 45°

.

34. A liquid crystal display apparatus according to claim 26, wherein:

where the positive phase plate is provided on both sides of the liquid crystal display device, a product (nx−

ny)×

d of a difference between the principal refractive index nx and the principal refractive index ny and a thickness d of the positive inclined phase plate is set to be in a range from 1 nm to 100 nm; and

where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

ny)×

d is set to be in a range from 2 nm to 200 nm.

35. A liquid crystal display apparatus according to claim 34, wherein:

where the positive phase plate is provided on both sides of the liquid crystal display device, a product (nx−

ny)×

d is set to be in a range from 5 nm to 40 nm; and

where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nx−

ny)×

d is set to be in a range from 10 nm to 80 nm.