High luminance polarizing plate, and liquid crystal panel and image display using same

• US 20060181662A1
• Filed: 03/01/2004
• Published: 08/17/2006
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Takahashi, Naoki, Kameyama, Tadayuki
• Granted Patent: US 7,746,424 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133528 Polarisers
• 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 2202/28 Adhesive materials or arrangements
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/8791 Arrangements for improving contrast, e.g. preventing reflection of ambient light

Abstract

A high-brightness polarizing plate of the present invention comprises a polarizing plate that comprises a polarizer and a protective film prepared on one or both sides of the polarizer, a brightness enhancement film and an adhesive layer through which the polarizing plate and the brightness enhancement film are laminated with the protective film interposed between them, wherein the protective film has an in-plane retardation Re of 0 to 10 nm and a thickness-direction retardation Rth of −30 to 10 nm, wherein Re=(nx−ny)d and Rth={(nx+ny)/(2−nz)}d. The high-brightness polarizing plate has a small color shift, and can be applied to various image displays such as liquid crystal displays.

Claims

1. A high-brightness polarizing plate, comprising:

a polarizing plate that comprises a polarizer and a protective film prepared on one or both sides of the polarizer;

a brightness enhancement film; and

an adhesive layer through which the polarizing plate and the brightness enhancement film are laminated with the protective film interposed between them, wherein

the protective film has an in-plane retardation Re of 0 to 10 nm and a thickness-direction retardation Rth of −

30 to 10 nm, wherein

Re=(nx−

ny)d and Rth={(nx+ny)/(2−

nz)}d, wherein nx is a refractive index in an X-axis direction in which a maximum in-plane refractive index is obtained, ny is a refractive index in a Y-axis direction perpendicular to the X-axis, nz is a refractive index in a Z-axis direction which is the film thickness direction, and d is a thickness (nm) of the protective film.

2. The high-brightness polarizing plate according to claim 1, wherein the protective film contains (A) a thermoplastic resin having a substituted and/or unsubstituted imide group in side chain and (B) a thermoplastic resin having a substituted and/or unsubstituted phenyl and nitrile groups in side chain.

3. The high-brightness polarizing plate according to claim 1, wherein the protective film is a biaxially stretched film.

4. The high-brightness polarizing plate according to claim 1, wherein the polarizer is an iodine-containing polyvinyl alcohol-based film.

5. The high-brightness polarizing plate according to claim 1, wherein the brightness enhancement film is an anisotropic reflection polarizer.

6. The high-brightness polarizing plate according to claim 5, wherein the anisotropic reflection polarizer is a composite of a cholesteric liquid crystal layer and a quarter wavelength plate.

7. The high-brightness polarizing plate according to claim 5, wherein the anisotropic reflection polarizer is an anisotropic multilayered thin film capable of transmitting linearly polarized light in one direction of vibration and reflecting linearly polarized light that in another direction of vibration.

8. The high-brightness polarizing plate according to claim 5, wherein the anisotropic reflection polarizer is a reflective grid polarizer.

9. The high-brightness polarizing plate according to claim 1, wherein the brightness enhancement film is an anisotropic scattering polarizer.

10. A high-brightness polarizing plate, comprising the high-brightness polarizing plate according to claim 1 and at least one optical film.

11. A liquid crystal panel, comprising a liquid crystal cell and the high-brightness polarizing plate according to claim 1 attached to at least one side of the liquid crystal cell.

12. A liquid crystal display, comprising the liquid crystal panel according to claim 11.

13. An image viewing display, comprising the high-brightness polarizing plate according to claim 1.