VERTICAL ALIGNMENT TYPE LIQUID CRYSTAL DISPLAY DEVICE WITH VIEWING ANGLE CHARACTERISTICS IMPROVED BY DISPOSING OPTICAL PLATES

• US 20090213313A1
• Filed: 02/09/2009
• Published: 08/27/2009
• Est. Priority Date: 02/27/2008
• Status: Active Grant

• Current Assignee: Stanley Electric Company Limited
• Original Assignee: Stanley Electric Company Limited
• Inventors: IWAMOTO, Yoshihisa
• Granted Patent: US 8,199,283 B2
• Time in Patent Office: Days
• US Class Current: 349/118
• 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 1/13712 the liquid crystal having negative dielectric anisotropy

Abstract

First and second polarizers are disposed in cross Nichol configuration. A liquid crystal cell is disposed between the two polarizers and establishes vertical alignment in a state of no voltage application. An even number of optical films having optical anisotropy and disposed between the liquid crystal cell and first polarizer. A retardation of the liquid crystal cell is in a range between 300 nm and 1500 nm; and each optical film satisfies nx>ny≧nz, an in-plane retardation is smaller than 300 nm, a thickness direction retardation is in a ranger between 50 nm and 300 nm, an angle between an in-plane slow axis of the optical film disposed nearest to the first polarizer and an absorption axis of the first polarizer is smaller than 45°, and the slow axes of mutually adjacent optical films are perpendicular to each other.

Claims

1. A liquid crystal display device comprising:

first and second polarizers in cross Nichol configuration;

a liquid crystal cell disposed between the first and second polarizers and establishing vertical alignment in a state of no voltage application; and

an even number of optical films having optical anisotropy and disposed between the liquid crystal cell and the first polarizer,

wherein;

a retardation of the liquid crystal cell is equal to or larger than 300 nm and equal to or smaller than 1500 nm; and

each of the optical films satisfies nx>

ny≧

nz where nx, ny and nz are x-, y- and z-components of a refractive index in which an x-axis is an in-plane slow axis azimuth of each of the optical films, a y-axis is an in-plane azimuth perpendicular to the x-axis and a z-axis is a direction perpendicular to a film surface, an in-plane retardation is equal to or smaller than 300 nm, a thickness direction retardation is equal to or larger than 50 nm and equal to or smaller than 300 nm, an angle between an in-plane slow axis of the optical film disposed nearest to the first polarizer and an absorption axis of the first polarizer is equal to or smaller than 45°

, and the slow axes of mutually adjacent optical films are perpendicular to each other.

2. The liquid crystal display device according to claim 1, wherein an in-plane retardation of each of the optical films is equal to or larger than 30 nm and equal to or smaller than 70 nm, and a thickness direction retardation is equal to or larger than 110 nm and equal to or smaller than 300 nm.

3. The liquid crystal display device according to claim 1, wherein an in-plane retardation of each of the optical films is equal to or larger than 100 nm and equal to smaller than 300 nm, and a thickness direction retardation is equal to or larger than 110 nm and equal to or smaller than 300 nm, and an angle between the in-plane slow axis of the optical film disposed nearest to the first polarizer and an absorption axis of the first polarizer is equal to or larger than 15°

and equal to or smaller than 45°

.

5. The liquid crystal display device according to claim 1, wherein a difference between an in-plane retardation of each of the optical films and an average of retardations of the optical films is equal to or smaller than 10 nm.

6. The liquid crystal display device according to claim 1, wherein the optical films have a same thickness and a same refractive index anisotropy.

7. The liquid crystal display device according to claim 1, wherein a total of thickness direction retardations of the optical films falls in a range between 0.5 times and 1 time the retardation of the liquid crystal cell.

8. The liquid crystal display device according to claim 1, further comprising a drive circuit for multiplex-driving the liquid crystal cell.

4. A liquid crystal display device comprising:

first and second polarizers in cross Nichol configuration;

a liquid crystal cell disposed between the first and second polarizers and establishing vertical alignment in a state of no voltage application; and

an odd number of three or more optical films having optical anisotropy and disposed between the liquid crystal cell and the first polarizer,

wherein;

a retardation of the liquid crystal cell is equal to or larger than 550 nm and equal to or smaller than 1500 nm; and

each of the optical films satisfies nx>

ny≧

nz where nx, ny and nz are x-, y- and z-components of a refractive index in which an x-axis is an in-plane slow axis azimuth of each of the optical films, a y-axis is an in-plane azimuth perpendicular to the x-axis and a z-axis is a direction perpendicular to a film surface, an in-plane retardation is equal to or larger than 30 nm and equal to or smaller than 300 nm, a thickness direction retardation is equal to or larger than 50 nm and equal to or smaller than 300 nm, an angle between an in-plane slow axis of the optical film disposed nearest to the first polarizer and an absorption axis of the first polarizer is equal to or larger than 45° and

equal to or smaller than 135°

, and the slow axes of mutually adjacent optical films are perpendicular to each other.

9. A liquid crystal display device comprising:

first and second polarizers in cross Nichol configuration;

a liquid crystal cell disposed between the first and second polarizers and establishing vertical alignment in a state of no voltage application; and

a first optical film disposed between the liquid crystal cell and the first polarizer and having optical anisotropy;

a second optical film disposed between the first optical film and the liquid crystal cell and having optical anisotropy; and

a third optical film disposed between the second polarizer and the liquid crystal cell and having optical anisotropy;

wherein;

each of the first to third optical films satisfies nx>

ny≧

nz where nx, ny and nz are x-, y- and z-components of a refractive index in which an x-axis is an in-plane slow axis azimuth of each of the optical films, a y-axis is an in-plane azimuth perpendicular to the x-axis and a z-axis is a direction perpendicular to a film surface, an in-plane retardation is larger than 0 nm and equal to or smaller than 300 nm, and a thickness direction retardation is equal to or larger than 50 nm and equal to or smaller than 300 nm;

a slow axis of the first optical film is parallel to an absorption axis of the first polarizer;

a slow axis of the second optical film and a slow axis of the third optical film are perpendicular to each other; and

an angle between an in-plane axis of the second optical film and an absorption axis of the first polarizer is in a range between 75° and

105°

.

10. The liquid crystal display device according to claim 9, wherein:

a retardation of the liquid crystal cell is in a range between 550 nm and 1080 nm; and

in-plane retardations of the first to third optical films are in a range between 30 nm and 70 nm.

11. The liquid crystal display device according to claim 9, wherein a total of thickness direction retardations of the first to third optical films falls in a range between 0.5 times and 1 time the retardation of the liquid crystal cell.

12. The liquid crystal display device according to claim 9, further comprising:

a fourth optical film disposed between the second optical film and the liquid crystal cell or between the third optical film and the liquid crystal cell and having an in-plane retardation smaller than 7 nm and a thickness direction retardation equal to or larger than 50 nm and equal to or smaller than 300 nm; and

a retardation of the liquid crystal cell is in a range between 460 nm and 1380 nm.

13. The liquid crystal display device according to claim 12, wherein a total of thickness direction retardations of the first to fourth optical films falls in a range between 0.5 times and 1 time the retardation of the liquid crystal cell.

14. The liquid crystal display device according to claim 9, further comprising

fifth and sixth optical films disposed between the second optical film and the liquid crystal cell or between the third optical film and the liquid crystal cell and having optical anisotropy,

wherein each of the fifth and sixth optical films satisfies nx>

ny≧

nz where nx, ny and nz are x-, y- and z-components of a refractive index in which an x-axis is an in-plane slow axis azimuth of each of the optical films, a y-axis is an in-plane azimuth perpendicular to the x-axis and a z-axis is a direction perpendicular to a film surface, an in-plane retardation of each of the fifth and sixth optical films is larger than 30 nm and equal to or smaller than 70 nm, a thickness direction retardation is equal to or larger than 50 nm and equal to or smaller than 300 nm, and a retardation of the liquid crystal cell is in a range between 510 nm and 1380 nm.

15. The liquid crystal display device according to claim 14, wherein a total of thickness direction retardations of the first to third optical films and the fifth and sixth optical films falls in a range between 0.5 times and 1 time the retardation of the liquid crystal cell.

16. The liquid crystal display device according to claim 9, wherein a difference between an in-plane retardation of each of the first to third optical films and an average of retardations of the first to third optical films is equal to or smaller than 10 nm.

17. A liquid crystal display device comprising:

a liquid crystal cell establishing vertical alignment in a state of not voltage application;

first and second polarizers in cross Nichol configuration and sandwiching the liquid crystal cell;

a first optical film disposed between the liquid crystal cell and the first polarizer and having optical anisotropy;

a second optical film disposed between the first optical film and the liquid crystal cell and having optical anisotropy;

a third optical film disposed between the second polarizer and the liquid crystal cell and having optical anisotropy; and

a fourth optical film disposed between the third optical film and the second polarizer and having optical anisotropy,

wherein;

each of the first to fourth optical films satisfies nx>

ny≧

nz where nx, ny and nz are x-, y- and z-components of a refractive index in which an x-axis is an in-plane slow axis azimuth of each of the optical films, a y-axis is an in-plane azimuth perpendicular to the x-axis and a z-axis is a direction perpendicular to a film surface, and the first to fourth optical films have approximately same optical characteristics;

a slow axis of the first optical film is approximately parallel to an absorption axis of the first polarizer;

a slow axis of the first optical film is approximately perpendicular to a slow axis of the second optical film;

a slow axis of the fourth optical film is approximately parallel to an absorption axis of the second polarizer; and

a slow axis of the third optical film is approximately perpendicular to a slow axis of the fourth optical film.

18. The liquid crystal display device according to claim 17, wherein each of the first to fourth optical films has an in-plane retardation Re satisfying 30 nm≦

Re≦

70 nm and a thickness direction retardation Rth satisfying 90 nm≦

Rth≦

300 nm, and a retardation of the liquid crystal cell is in a range between 500 nm and 1500 nm.

19. The liquid crystal display device according to claim 17, wherein a total of thickness direction retardations of the first to fourth optical films falls in a range between 0.5 times and 1 time the retardation of the liquid crystal cell.

20. The liquid crystal display device according to claim 17, further comprising a drive circuit for multiplex-driving the liquid crystal cell.

21. The liquid crystal display device according to claim 17, further comprising a C plate disposed between the second optical film and the liquid crystal cell or between the third optical film and the liquid crystal cell.