Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-04-20
2001-05-22
Ullah, Akm E. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06236439
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wide viewing angle polarizing plate suitable for the improvement in the viewability of transmission type, reflection type or amphibious liquid crystal display, etc.
The present application is based on Japanese Patent Applications No. Hei. 10-126882 and No. Hei. 11-75728, which are incorporated herein by reference.
2. Description of the Related Art
As a wide viewing angle polarizing plate intended for the expansion of the viewing angle or the compensation for the change in phase difference of liquid crystal display there has been heretofore known one comprising a laminate of a polarizing plate and a light diffusing plate or phase difference plate Japanese Patent Publications No. Hei. 9-258013 and 9-325216. However, this wide viewing angle polarizing plate is disadvantageous in that it is liable to contrast drop or blur of display image or leaves something to be desired in the expansion of viewing angle.
SUMMARY OF THE INVENTION
It is an object of the present invention to develop a wide viewing angle polarizing plate which, when provided in a liquid crystal display on the viewing side thereof, acts to compensate for the loss of viewing angle by phase difference as well as expand the viewing angle by light diffusion and thus causes little or no contrast drop or display image blur and a liquid crystal display comprising such a wide viewing angle polarizing plate.
The present invention provides a wide viewing angle polarizing plate comprising a laminate of a polarizing plate and a birefringent film having an in-plane average phase difference of from 50 nm to 200 nm, characterized in that said birefringent film comprises a transparent resin film having microscopic regions dispersed therein and satisfies the relationships &Dgr;n
2
≦0.03 and &Dgr;n
1
>&Dgr;n
2
supposing that the direction of the axis along which linearly polarized light exhibits the maximum transmission is &Dgr;n
2
direction, the difference in refractive index between microscopic regions in &Dgr;n
2
direction and other portions is &Dgr;n
2
, the direction perpendicular to &Dgr;n
2
direction is &Dgr;n
1
direction and the difference in refractive index between microscopic regions in &Dgr;n
1
direction and other portions is &Dgr;n
1
, and &Dgr;n
1
direction and the retardation axis of said birefringent film and the transmission axis of said polarizing plate are parallel to each other.
In accordance with the present invention, the arrangement of a birefringent film having a predetermined average phase difference such that its retardation axis is parallel to the transmission axis of a polarizing plate makes it possible to inhibit the drop of brightness or contrast in front direction perpendicular to the polarizing plate without being affected by the phase difference in the birefringent film and allows the phase difference in the birefringent film to compensate for the change in the state of linearly polarized light by the birefringence of the liquid crystal cell and apparent deviation in the orthogonal relationship between the linearly polarized light and the absorption axis of the polarizing plate as viewed obliquely during black display, making it possible to inhibit gradation inversion or contrast drop as well as provide a white display having a good viewability and a wide viewing angle attained by scattering and diffusion.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.
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Patent Abstracts of Japan vol. 098, No. 004 Mar. 31, 1998 & JP 09 325216 A (Nitto Denko Corp) Dec. 16, 1997 *Abstract.
Patent Abstracts of Japan vol. 098, No. 002, Jan. 30, 1998 & JP 274108 A (Teijin Ltd) Oct. 21, 1997 *Abstract.
Miyatake Minoru
Saiki Yuji
Sakuramoto Takafumi
Yoshimi Hiroyuki
Nitto Denko Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Ullah Akm E.
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