LIQUID CRYSTAL DISPLAY DEVICE

• US 20070126960A1
• Filed: 12/04/2006
• Published: 06/07/2007
• Est. Priority Date: 12/05/2005
• Status: Active Grant

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Toshiba Mobile Display Company Limited (Japan Display Incorporated)
• Inventors: JOTEN, Kazuhiro
• Granted Patent: US 7,609,346 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G02F 2413/02 Number of plates being 2
• CPC Class Codes: G02F 2413/07 All plates on one side of the LC cell
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation

Abstract

A liquid crystal display device includes a liquid crystal display panel which is configured such that a liquid crystal layer including liquid crystal molecules, which are twist-aligned at a twist angle of 70°±10°, is held between a first substrate and a second substrate, and an optical element which is provided on an outer surface of the second substrate. The optical element includes a polarizer plate, a first retardation plate which imparts a phase difference of a ½ wavelength, and a second retardation plate which imparts a phase difference of a ¼ wavelength, and a retardation value Δn·d of the liquid crystal layer is set at 200 ±30 nm, where Δn is a refractive index anisotropy of the liquid crystal layer and d is a thickness of the liquid crystal layer.

Claims

1. A liquid crystal display device comprising:

a liquid crystal display panel which is configured such that a liquid crystal layer including liquid crystal molecules, which are twist-aligned at a twist angle of 70°

±

10°

, is held between a first substrate having a plurality of reflection patterns protruding from a major surface of the first substrate and a second substrate which is disposed to be opposed to the first substrate; and

an optical element which is provided on an outer surface of the second substrate, wherein the optical element includes a polarizer plate, a first retardation plate which is disposed between the polarizer plate and the liquid crystal display panel and imparts a phase difference of a ½

wavelength between light rays of a predetermined wavelength, which pass through a fast axis and a slow axis of the first retardation plate, and a second retardation plate which is disposed between the first retardation plate and the liquid crystal display panel and imparts a phase difference of a ¼

wavelength between light rays of a predetermined wavelength, which pass through a fast axis and a slow axis of the second retardation plate, and

a retardation value Δ

n·

d of the liquid crystal layer is set at 200 ±

30 nm, where Δ

n is a refractive index anisotropy of the liquid crystal layer and d is a thickness of the liquid crystal layer.

2. The liquid crystal display device according to claim 1, wherein a maximum inclination angle of the reflection pattern is 9°

±

2°

, in a case where the maximum inclination angle is an inclination angle with a highest degree of inclination angles of the reflection pattern relative to the major surface of the substrate.

3. The liquid crystal display device according to claim 1, wherein the reflection pattern has such a shape as to have a major axis in a plane of the major surface of the substrate.

4. The liquid crystal display device according to claim 3, wherein the major axis of each of the reflection patterns is substantially parallel to a horizontal direction of the major surface of the substrate.

5. The liquid crystal display device according to claim 1, wherein when a horizontal direction of the major surface of the substrate is a reference azimuth, a counterclockwise direction relative to the reference azimuth is a positive direction and a clockwise direction relative to the reference azimuth is a negative direction, a director of the liquid crystal molecules is set within a range of 225°

±

20°

or a range of 315°

±

20°

relative to the reference azimuth.

6. The liquid crystal display device according to claim 1, wherein when a horizontal direction of the major surface of the substrate is a reference azimuth, a director of the liquid crystal molecules is set at 270°

relative to the reference azimuth, an absorption axis of the polarizer plate is set at 15°

±

0.5°

relative to the reference azimuth, the slow axis of the first retardation plate is set at 30°

±

0.5°

relative to the reference azimuth, and the slow axis of the second retardation plate is set at 90°

±

0.5°

relative to the reference azimuth.

7. The liquid crystal display device according to claim 1, wherein with respect to at least one of the first retardation plate and the second retardation plate, an Nz coefficient, which is defined by (nx−

nz)/(nx−

ny), is set in a range of less than 1, where nx and ny are refractive indices in mutually perpendicular directions in a plane of said at least one of the first retardation plate and the second retardation plate, and nz is a refractive index in a normal direction to the plane.