Liquid crystal display device with retardation layer

• US 7,423,715 B2
• Filed: 08/18/2004
• Issued: 09/09/2008
• Est. Priority Date: 08/20/2003
• Status: Expired due to Fees

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology Co Ltd (Japan Display Incorporated)
• Inventors: Hisatake, Yuzo
• Primary Examiner(s): Schechter; Andrew
• Assistant Examiner(s): Nguyen; Hoan C
• Application Number:
  US10/920,354
• Publication Number:
  US 20050275780A1
• Time in Patent Office: 1,483 Days
• Field of Search: 349/117, 349119-121, 349/105, 349 98-102, 349/118
• US Class Current: 349/119
• CPC Class Codes: G02F 1/133632 with refractive index ellipsoid inclined relative to the LC-layer surface
• CPC Class Codes: G02F 1/136222 Colour filters incorporated in the active matrix substrate
• 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
• CPC Class Codes: G02F 2413/105 with varying inclination in thickness direction, e.g. hybrid oriented discotic LC

Abstract

A liquid crystal display device includes a liquid crystal panel having a structure in which a liquid crystal layer LQ is held between a pair of electrode substrates AR, CT, a pair of polarizers PL which hold the liquid crystal panel therebetween, and a pair of optical retardation plates RT arranged between the liquid crystal panel and the pair of polarizers PL. Each optical retardation plate RT has a refractive anisotropy in which average refractive indices nx, ny, and nz in an x-axis direction, a y-axis direction, and a z-axis direction being perpendicular to each other satisfy nx>ny>nz in a state when the z-axis direction conforms to the normal direction. The x-axis direction of each optical retardation plate RT is almost parallel to the transmission axis of the polarizer PL adjacent to a corresponding optical retardation plates RT.

Claims

1. A liquid crystal display device comprising:

a liquid crystal cell in which liquid crystal molecules are held between a pair of substrates that produce an electric field corresponding to a voltage applied thereto; and

a pair of optical retardation plates arranged to hold said liquid crystal cell therebetween;

wherein each of said optical retardation plates includes first and second optical films stacked in a thickness direction to form an optical film stack, said first optical film includes a plurality of refractive elliptic bodies having optical axes which are tilted to have one component along the thickness direction and another component directed to a first predetermined side of the thickness direction of the optical film stack and whose tilt angles are set to have slight differences consecutively in the thickness direction, and

said second optical film includes a plurality of refractive elliptic bodies having optical axes which are tilted to have one component along the thickness direction of the optical film stack and another component directed away from said first predetermined side and whose tilt angles are set to have slight differences consecutively in the thickness direction.

2. The liquid crystal display device according to claim 1, wherein said pair of optical retardation plates are in a crossed Nicol, and a thickness t of each optical retardation plate satisfies relational expressions given by 30 nm≦

(nx−

ny)t≦

70 nm and 100 nm≦

(nx−

nz)t≦

140 nm, where nx, ny , and nz are average refractive indices in and x-axis direction, a y-axis direction, and a z-axis direction, respectively.

3. The liquid crystal display device according to claim 1, wherein said liquid crystal cell is divided into two domains.

4. The liquid crystal display device according to claim 1, wherein said optical retardation plate includes a negative biaxial retardation plate.

5. The liquid crystal display device according to claim 4, wherein said biaxial retardation plate has in-plane retardation which compensates for visual angle dependence of a pair of polarizers that hold said retardation plate and liquid crystal cell therebetween.

6. The liquid crystal display device according to claim 5, wherein said liquid crystal cell is divided into domains in which alignment directions of the liquid crystal molecules make angles.

7. The liquid crystal display device according to claim 6, wherein said liquid crystal cell is divided into two domains.

8. The liquid crystal display device according to claim 6, wherein said liquid crystal cell is divided into four domains.

9. A liquid crystal display device comprising:

a liquid crystal cell in which liquid crystal molecules are held between a pair of substrates that produce an electric field corresponding to a voltage applied thereto, set in an alignment substantially vertical to each substrate plane when the voltage is not applied to said substrates, and set in an alignment that directors of said molecules are tilted in a predetermined cross section perpendicular to said substrate plane when the voltage is applied to said substrates; and

a pair of optical retardation plates arranged to hold said liquid crystal cell therebetween;

wherein each of said optical retardation plates includes first and second optical films stacked in a thickness direction to form an optical film stack and to have negative retardation that presents an optical axis set in a direction substantially vertical to each substrate plane, said first optical film includes a plurality of refractive elliptic bodies having optical axes which are tilted on a same side as that of said liquid crystal molecules in said predetermined cross section, which are tilted to have one component along the thickness direction and another component directed to a first predetermined side of the thickness direction of the optical film stack, and whose tilt angles are set to have slight differences consecutively in the thickness direction, and said second optical film includes a plurality of refractive elliptic bodies having optical axes which are tilted on and opposite side as that of said liquid crystal molecules in said predetermined cross section, which are titled to have one component along the thickness direction of the optical film stack and another component directed away from said first predetermined side, and whose tilt angles are set to have slight differences consecutively in the thickness direction.