Laminated quarter-wave plate or circularly polarizing plate, liquid-crystal display device using the same and method for producing the same

• US 20030067574A1
• Filed: 10/02/2002
• Published: 04/10/2003
• Est. Priority Date: 10/03/2001
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Yamaoka, Takashi, Yoshimi, Hiroyuki, Sasaki, Shinichi
• Granted Patent: US 6,762,811 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• 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 1/133634 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 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n

Abstract

A laminated quarter-wave plate having: a laminate of a quarter-wave plate and a half-wave plate, wherein: the quarter-wave plate and the half-wave plate are laminated on each other so that directions of in-plane slow axes intersect each other; and each of the quarter-wave plate and the half-wave plate satisfies a relation Nz=(nx−nz)/(nx−ny)>1.05 in which nx and ny are in-plane main refractive indices, and nz is a thickness wise refractive index; and a circularly polarizing plate having: a laminate of a laminated quarter-wave plate defined above and a polarizer.

Claims

1. A laminated quarter-wave plate comprising:

a quarter-wave plate; and

a half-wave plate laminated on said quarter-plate, so that directions of in-plane slow axes of said plates intersect each other;

wherein each of said quarter-wave plate and said half-wave plate satisfies a relation Nz=(nx−

nz)/(nx−

ny)>

1.05 in which nx and ny are in-plane main refractive indices, and nz is a thicknesswise refractive index.

2. A circularly polarizing plate comprising:

a laminated quarter-wave plate according to claim 1 and a polarizer laminated on said laminated quarter-wave plate.

3. A laminated quarter-wave plate according to claim 1, further comprising a pressure sensitive adhesive layer provided on at least one of opposite surfaces of said laminated quarter-wave plate.

4. A circularly polarizing plate according to claim 2, further comprising a pressure sensitive adhesive layer provided on at least one of opposite surfaces of said circularly polarizing plate.

5. A liquid-crystal display device comprising:

a liquid-crystal cell; and

a laminated quarter-wave plate according to claim 1 and disposed on at least one of opposite surfaces of said liquid-crystal cell.

6. A liquid-crystal display device comprising:

a liquid-crystal cell; and

a laminated quarter-wave plate according to claim 3 and disposed on at least one of opposite surfaces of said liquid-crystal cell.

7. A liquid-crystal display device comprising:

a liquid-crystal cell; and

a circularly polarizing plate according to claim 2 and disposed on at least one of opposite surfaces of said liquid-crystal cell.

8. A liquid-crystal display device comprising:

a liquid-crystal cell; and

a circularly polarizing plate according to claim 4 and disposed on at least one of opposite surfaces of said liquid-crystal cell.

9. A method of producing a phase retarder satisfying a relation Nz=(nx−

nz)/(nx−

ny)>

1.05 in which nx and ny are in-plane main refractive indices, and nz is a thicknesswise refractive index, said method comprising the step of;

stretching a transparent polymer film with a thickness of 5 to 500 μ

m by one of tenter lateral stretching and biaxial stretching.