LIQUID CRYSTAL DISPLAY DEVICE, OPTICAL FILM, AND TERMINAL DEVICE

• US 20080100786A1
• Filed: 10/02/2007
• Published: 05/01/2008
• Est. Priority Date: 10/27/2006
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd.
• Original Assignee: NEC LCD Technologies Limited (NEC Corporation)
• Inventors: Sumiyoshi, Ken, Matsushima, Jin
• Granted Patent: US 7,830,481 B2
• Time in Patent Office: Days
• US Class Current: 349/118
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133631 with a spatial distribution of the retardation value
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• 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 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2413/03 Number of plates being 3
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation

Abstract

A first polarizer and a second polarizer have respective absorption axes extending approximately perpendicularly to each other, and a first retardation plate and a third retardation plate have respective slow axes extending approximately perpendicularly to each other. The first retardation plate and the third retardation plate have respective retardations that are approximately equal to each other, and have respective Nz coefficients that are approximately equal to each other. A second retardation plate and a liquid crystal layer in a transmissive display area have a slow axis and an orientation axis, respectively, extending approximately perpendicularly to each other. The second retardation plate and the liquid crystal layer in the transmissive display area have respective retardations that are approximately equal to each other.

Claims

1. A liquid crystal device comprising first and second substrates and liquid crystal layers sandwiched between said first and second substrates, and including a reflective display area and a transmissive display area as pixel areas, the arrangement being such that said liquid crystal layer in at least said transmissive display area can be energized in a lateral electric field mode when a voltage is applied parallel to the plane of said substrates, wherein

a first retardation plate and a first polarizer are stacked on a surface of said first substrate remote from said liquid crystal layer in an order toward said first substrate, and a second retardation plate, a third retardation plate, and a second polarizer are stacked on a surface of said second substrate remote from said liquid crystal layer in an order toward said second substrate;

said first retardation plate and said third retardation plate have respective slow axes extending substantially perpendicularly to each other, and said second retardation plate and said liquid crystal layer in said transmissive display area have a slow axis and an orientation axis, respectively, extending substantially perpendicularly to each other;

the retardation with respect to light applied from the direction normal to said first retardation plate to said first retardation plate is defined as Re1(0), the retardation with respect to light applied from the air to said first retardation plate at an angle of 40 degrees from the normal direction to said first retardation plate toward the slow axis of said first retardation plate is defined as Re1x(40), and the retardation with respect to light applied from the air to said first retardation plate at an angle of 40 degrees from the direction normal to said first retardation plate toward a direction perpendicular to the slow axis of said first retardation plate is defined as Re1y(40);

the retardation with respect to light applied from the direction normal to said second retardation plate to said second retardation plate is defined as Re2(0), the retardation with respect to light applied from the air to said second retardation plate at an angle of 40 degrees from the direction normal to said second retardation plate toward the slow axis of said second retardation plate is defined as Re2x(40), and the retardation with respect to light applied from the air to said second retardation plate at an angle of 40 degrees from the direction normal to said second retardation plate toward a direction perpendicular to the slow axis of said second retardation plate is defined as Re2y(40);

the retardation with respect to light applied from the direction normal to said third retardation plate to said third retardation plate is defined as Re3(0), the retardation with respect to light applied from the air to said third retardation plate at an angle of 40 degrees from the direction normal to said third retardation plate toward the slow axis of said third retardation plate is defined as Re3x(40), and the retardation with respect to light applied from the air to said third retardation plate at an angle of 40 degrees from the direction normal to said third retardation plate toward a direction perpendicular to the slow axis of said third retardation plate is defined as Re3y(40);

the retardation with respect to light applied from the direction normal to said liquid crystal layer in said transmissive display area to said liquid crystal layer is defined as ReLC(0), the retardation with respect to light applied from the air to said liquid crystal layer at an angle of 40 degrees from the direction normal to said liquid crystal layer toward the orientation axis of said liquid crystal layer is defined as ReLCx(40), and the retardation with respect to light applied from the air to said liquid crystal layer at an angle of 40 degrees from the direction normal to said liquid crystal layer toward a direction perpendicular to the orientation axis of said liquid crystal layer is defined as ReLCy(40); and

Re1(0) and Re3(0) are approximately equal to each other, Re1(0), Re1x(40), Re1y(40), Re3(0), Re3x(40), and Re3y(40) are approximately equal to each other, Re2(0) and ReLC(0) are approximately equal to each other, Re2x(40) and ReLCy(40) are approximately equal to each other, and Re2y(40) and ReLCx(40) are approximately equal to each other.

2. The liquid crystal display device according to claim 1, wherein the retardation of each of said first retardation plate, said liquid crystal layer in said transmissive display area, said second retardation plate and said third retardation plate is approximately λ

/2.

3. The liquid crystal display device according to claim 1, wherein said second retardation plate has an Nz coefficient in the range from −

0.2 to 0.4.

4. The liquid crystal display device according to claim 1, wherein said second retardation plate has an Nz coefficient of substantially nil.

5. The liquid crystal display device according to claim 1, wherein each of said first retardation plate and said third retardation plate has an Nz coefficient in the range from 0.3 to 0.8.

6. The liquid crystal display device according to claim 1, wherein each of said first retardation plate and said third retardation plate has an Nz coefficient of approximately 0.5.

7. The liquid crystal display device according to claim 1, wherein a disposition error with respect to the slow axis of said first retardation plate is in the range from −

2.8 degrees to 2.6 degrees, a disposition error with respect to the slow axis of said second retardation plate is in the range from −

2.6 degrees to 2.6 degrees, a disposition error with respect to the slow axis of said third retardation plate is in the range from −

2.6 degrees to 2.8 degrees, and a disposition error with respect to the orientation axis of said liquid crystal layer is in the range from −

2.6 degrees to 2.6 degrees.

8. The liquid crystal display device according to claim 1, wherein a retardation error of said first retardation plate is in the range from −

51.9 nm to 48.9 nm, a retardation error of said second retardation plate is in the range from −

16.8 nm to 15.7 nm, a retardation error of said third retardation plate is in the range from −

48.0 nm to 49.9 nm and a retardation error of said liquid crystal layer is in the range from −

16.1 nm to 17.2 nm.

11. A terminal device incorporating a liquid crystal display device according to claim 1.

9. An optical film comprising:

a polarizer; and

a retardation plate having a retardation of approximately λ

/2 and an Nz coefficient in the range from 0.3 to 0.8, preferably approximately 0.5;

said polarizer and said retardation plate being stacked together.

10. An optical film comprising:

a polarizer; and

a retardation plate having a retardation of approximately λ

/2 and an Nz coefficient in the range from 0.3 to 0.8, preferably approximately 0.5; and

a retardation of approximately λ

/2 and an Nz coefficient in the range from −

0.2 to 0.4, preferably approximately nil;

said polarizer and said retardation plates being stacked together in the order named.