Optical device, polarizing plate, diffuser, diffusing film, polarizing film and liquid crystal image display apparatus

• US 7,573,549 B2
• Filed: 08/27/2007
• Issued: 08/11/2009
• Est. Priority Date: 08/29/2006
• Status: Active Grant

• Current Assignee: Toppan Printing Co., Ltd. (TOPPAN Holdings, Inc.)
• Original Assignee: Toppan Printing Co., Ltd. (TOPPAN Holdings, Inc.)
• Inventors: Nishihara, Takashi, Sakakibara, Shigetomo, Homma, Hideaki, Tochigi, Yusuke
• Primary Examiner(s): Nelms; David
• Assistant Examiner(s): Vu; Phu
• Application Number:
  US11/892,787
• Publication Number:
  US 20080055523A1
• Time in Patent Office: 715 Days
• Field of Search: 349/112
• US Class Current: 349/112
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• 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 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence

Abstract

An optical device includes a plastic-based film and a diffusing layer. The diffusing layer includes inner scattering elements that selectively scatter visible light having a wavelength range, and has pencil hardness of more than 2H under a 500 g-load specified in ISO/DIS 15184. When the optical device is arranged at a front side of a liquid crystal display apparatus that displays color near 8 test colors specified in CIE 1974, as a test color, chrominance Δu′v′ of less than 0.05 is obtained based on a chromaticity coordinate (u₀′, v₀′) of CIE1976UCS observed in the front surface 100A1 of the liquid crystal display apparatus and a chromaticity coordinate (u′, v′) observed at an observation angle of ±60 degrees in horizontal and vertical directions of a screen of the liquid crystal display apparatus when a direction perpendicular to the screen is assumed to be 0 degrees.

Claims

1. An optical device for a liquid crystal display apparatus that displays an image, the optical device being arranged at a front side of the liquid crystal display apparatus, comprising:

a plastic-based film; and

a diffusing layer formed at least one surface of the plastic-based film and scatters light that passes through the diffusing layer, the diffusing layer including;

a medium; and

inner scattering elements that selectively Mie-scatter visible light having a wavelength range of 400 nm to 500 nm into the medium, the inner scattering elements having a refraction index different from a refraction index of the medium, wherein the diffusing layer has pencil hardness of equal to or more than 2H under a 500 g-load specified in ISO/DIS 15184, and

wherein, when the optical device is arranged at the front side of the liquid crystal display apparatus that displays color near eight test colors specified in CIE 1974, as a test color, the optical device being formed so that chrominance Δ

u′

v′

obtained according to the following Equation 1 is equal to or less than 0.05, based on a chromaticity coordinate (u₀′

, v₀′

) of CIE1976UCS observed in the front side and a chromaticity coordinate (u′

, v′

) of CIE1976UCS observed at an observation angle of ±

60 degrees in horizontal and vertical directions of a screen of the liquid crystal display apparatus when a direction perpendicular to the screen is assumed to be 0 degrees

Δ

u′

v′

={(u′

−

u₀′

)²+(v′

−

v₀′

)²}^0.5  

 

[Equation 1].

2. The optical device according to claim 1, wherein the thickness of the diffusing layer is 2 μ

m to 30 μ

m.

3. The optical device according to claim 1, wherein the medium of the diffusing layer is made of a radiation curable resin, and the inner scattering elements are dispersed in the radiation curable resin.

4. The optical device according to claim 1, wherein the size of the inner scattering elements is 0.5 μ

m to 3.0 μ

m.

5. The optical device according to claim 1, wherein a difference in refraction index between the medium and the inner scattering elements is 0.05 to 0.6.

6. The optical device according to claim 1, wherein the inner scattering elements are particulate.

7. The optical device according to claim 1, wherein a surface of the diffusing layer is formed to be uneven.

8. The optical device according to claim 7, wherein at least one of the group consisting of some of the inner scattering elements and unevenness forming particles mixed into the medium of the diffusing layer, project from the surface of the diffusing layer.

9. The optical device according to claim 7, wherein the surface of the diffusing layer is formed to be uneven by an emboss process.

10. The optical device according to claim 1, wherein the optical device is used for the liquid crystal display apparatus having a vertical-aligned liquid crystal cell.

11. A polarizing plate comprising:

a polarizing layer; and

the optical device according to claim 1, the optical device being disposed on the polarizing layer.

12. A liquid crystal display apparatus comprising the polarizing plate according to claim 11, the polarizing plate being arranged at a front side at which an image of the liquid crystal display apparatus is displayed.

13. A liquid crystal image display apparatus comprising:

a diffuser;

an analyzer;

a first biaxial phase difference optical device;

a vertical alignment liquid crystal cell;

a second biaxial phase difference optical device;

a polarizer; and

a backlight, which are arranged in order from a front side to a rear side, wherein

the diffuser includes inner scattering elements that cause Mie scattering;

the analyzer and the polarizer are arranged in cross-Nicol condition;

slow axes of the first and second biaxial phase difference optical devices are arranged to be perpendicular to an absorption axis of the analyzer or the polarizer;

the first and second biaxial phase difference optical devices compensate a phase difference of the liquid crystal cell; and

the diffuser suppresses color shift in halftone.

14. The liquid crystal image display apparatus according to claim 13, wherein a spectral transmittance of light in an inclined direction during black image is displayed on the liquid crystal image display apparatus has the minimum value in a wavelength range of 410 nm to 610 nm.

15. The liquid crystal image display apparatus according to claim 13, wherein the first and second biaxial phase difference optical devices have the same phase difference.

16. The liquid crystal image display apparatus according to claim 13, further comprising a brightness enhancement film which enhances front luminance, and is arranged at a rear side of the liquid crystal cell.

17. A diffuser for use in a liquid crystal image display apparatus having a vertical-aligned liquid crystal cell, the diffuser being arranged at a front side at which an image of the liquid crystal panel is displayed, the diffuser suppressing color variation of the image which occurs when an observation angle at the front side is changed, wherein

the diffuser has a diffusion characteristic of diffusing equal to or more than 10% of parallel light ray incident in a front direction perpendicular to the front side with an angle range of 35°

to 55°

with respect to the front direction and diffusing equal to or less than 7% of the parallel light ray with an angle range of 60°

to 90°

with respect to the front direction.

18. A diffusing film that is arranged at a front side at which an image of a vertical alignment type liquid crystal panel is displayed, the diffusing film diffusing light incident into the liquid crystal panel, comprising:

a plastic-based film; and

the diffuser according to claim 17, the diffuser being provided on the plastic-based film.

19. A polarizing film that is arranged at a front side at which an image of a vertical alignment type liquid crystal panel is displayed, the polarizing film polarizing light incident into the liquid crystal panel, comprising the diffuser according to claim 17, the diffuser being arranged at the front side at which the image is displayed.

20. A liquid crystal image display apparatus having a vertical alignment type liquid crystal panel, comprising the diffuser according to claim 17, the diffuser being arranged at a front side at which an image of the liquid crystal panel is displayed.