Liquid crystal display device

• US 20030210365A1
• Filed: 05/02/2003
• Published: 11/13/2003
• Est. Priority Date: 05/10/2002
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Advanced Display Technologies, Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Satake, Tetsuya, Kurata, Tetsuyuki, Koyama, Hitoshi, Nishioka, Takahiro
• Granted Patent: US 6,801,283 B2
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133541 Circular polarisers
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/1398 the twist being below 90°
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G02F 2413/04 Number of plates greater than or equal to 4
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation

Abstract

A liquid crystal display device has an elliptic polarizer consisting of a polarizer, a first retarder, and a second retarder, and a reflector reflecting light in a visual light range. Optimal values for a twist angle of a liquid crystal layer, an angle between a transmission axis of the polarizer and a slow axis of the first retarder, an angle between the slow axis of the first retarder and a slow axis of the second retarder, and a product of birefringence Δn of liquid crystal material used in the liquid crystal layer and a thickness d of the liquid crystal layer are evaluated.

Claims

1. A liquid crystal display device having a reflective liquid crystal display element, the reflective liquid crystal display element comprising:

a set of substrates having an electrode to apply a voltage to a liquid crystal layer;

a twisted liquid crystal layer interposed between the substrates;

an elliptic polarizer consisting of a polarizer, a first retarder, and a second retarder having a slow axis substantially parallel to a bisector of alignment directions of liquid crystal material at substrate interfaces, and producing retardation of less than 140 nm; and

a reflector reflecting light in a visible light range;

wherein a product (nm) of birefringence Δ

n of liquid crystal material used in the liquid crystal layer and a thickness d of the liquid crystal layer is not less than 120 nm, and not more than a value given by Formula 1;

$\begin{array}{cc}\text{Formula <br><br> <br><br>1;<br><br>}<br><br><br><br>89.2+\frac{1.42\times <br><br>{10}^6}{{\left[\mathrm{Re}+\left({\mathrm{Re}}^{\mathrm{\prime <br><br>}}-270\right)·<br><br>\cos <br><br>\left(2<br><br><br><br>{\mathrm{\alpha <br><br>}}_3-{\mathrm{\alpha <br><br>}}_2<br><br>\right)\right]}^2}& \text{\hspace{1em}<br><br>}\end{array}$

when a twist angle in the liquid crystal layer is in a range of 63 to 77 degrees, an angle between a transmission axis α

1 of the polarizer and a slow axis α

2 of the first retarder is in a range of 5 to 25 degrees or in a range of 95 to 115 degrees, an angle between the slow axis α

2 of the first retarder and a slow axis α

3 of the second retarder is in a range of 50 to 70 degrees, retardation produced by the second retarder is Re (nm), and retardation produced by the first retarder is Re′

(nm).

2. A liquid crystal display device according to claim 1, wherein the twist angle in the liquid crystal layer is in a range of 65 to 75 degrees.

3. A liquid crystal display device according to claim 1, wherein the angle between the transmission axis Δ

1 of the polarizer and the slow axis α

2 of the first retarder is in a range of 10 to 20 degrees or in a range of 100 to 110 degrees.

4. A liquid crystal display device according to claim 2, wherein the angle between the transmission axis α

1 of the polarizer and the slow axis α

2 of the first retarder is in a range of 10 to 20 degrees or in a range of 100 to 110 degrees.

5. A liquid crystal display device according to claim 1, wherein the angle between the slow axis α

2 of the first retarder and the slow axis α

3 of the second retarder is in a range of 55 to 65 degrees.

6. A liquid crystal display device according to claim 2, wherein the angle between the slow axis α

2 of the first retarder and the slow axis α

3 of the second retarder is in a range of 55 to 65 degrees.

7. A liquid crystal display device according to claim 3, wherein the angle between the slow axis α

2 of the first retarder and the slow axis α

3 of the second retarder is in a range of 55 to 65 degrees.

8. A liquid crystal display device according to claim 1, wherein the product of birefringence Δ

n of liquid crystal material used in the liquid crystal layer and the thickness d of the liquid crystal layer is not less than 130 nm.

9. A liquid crystal display device according to claim 2, wherein the product of birefringence Δ

n of liquid crystal material used in the liquid crystal layer and the thickness d of the liquid crystal layer is not less than 130 nm.

10. A liquid crystal display device according to claim 3, wherein the product of birefringence Δ

n of liquid crystal material used in the liquid crystal layer and the thickness d of the liquid crystal layer is not less than 130 nm.

11. A liquid crystal display device according to claim 5, wherein the product of birefringence Δ

n of liquid crystal material used in the liquid crystal layer and the thickness d of the liquid crystal layer is not less than 130 nm.

12. A liquid crystal display device according to claim 1, further having a transmissive liquid crystal display element, the transmissive liquid crystal display element comprising:

a second elliptic polarizer consisting of a second polarizer, a third retarder, and a fourth retarder; and

a second twisted liquid crystal layer interposed between the substrates,

wherein a slow axis of the fourth retarder is inclined with respect to the bisector of alignment directions of liquid crystal material at substrate interfaces at −

15 to +15 degrees, and the fourth retarder produces retardation of 80 nm to 140 nm.

13. A liquid crystal display device according to claim 12, wherein the slow axis of the fourth retarder is inclined with respect to the bisector of alignment directions of liquid crystal material at substrate interfaces at −

10 to +10 degrees.

14. A liquid crystal display device according to claim 12, wherein an angle between a transmission axis of the second polarizer and a slow axis of the third retarder is in a range of 63 to 70 degrees or in a range of 153 to 160 degrees, and an angle between the slow axis of the third retarder and a slow axis of the fourth retarder is in a range of 108 to 115 degrees.

15. A liquid crystal display device according to claim 13, wherein an angle between a transmission axis of the second polarizer and a slow axis of the third retarder is in a range of 63 to 70 degrees or in a range of 153 to 160 degrees, and an angle between the slow axis of the third retarder and a slow axis of the fourth retarder is in a range of 108 to 115 degrees.

16. A liquid crystal display device according to claim 12, wherein the fourth retarder is a hybrid alignment liquid crystal film.

17. A liquid crystal display device according to claim 13, wherein the fourth retarder is a hybrid alignment liquid crystal film.

18. A liquid crystal display device according to claim 14, wherein the fourth retarder is a hybrid alignment liquid crystal film.