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Normally White Negative Birefringence Film Compensated Twisted Nematic Liquid Crystal Displays with Improved Optical Perfromance

IP.com Disclosure Number: IPCOM000106031D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Ong, HL: AUTHOR

Abstract

Disclosed are multicolor normally white (NW) twisted nematic (TN) LCDs using negative birefringence compensation film to improve the contrast ratio and viewing angle.

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Normally White Negative Birefringence Film Compensated Twisted Nematic Liquid Crystal Displays with Improved Optical Perfromance

      Disclosed are multicolor normally white (NW) twisted nematic
(TN) LCDs using negative birefringence compensation film to improve
the contrast ratio and viewing angle.

      In the presently disclosed NW TN LCD geometry, an optical
compensation film with a negative birefringence is used to improve
the LCD optical performance.  The compensation film is used to
compensate the optically black field-on state and reduce the light
leakage in the off-viewing angle in the optically black state.
Therefore, the contrast ratio and viewing angle is significantly
improved.  The compensation film has a negative birefringence and
vertical optical axis orientation.

      Recently, [*]  based this on the same concept, but with the use
of a neutral cholesteric LC (CLC) cell as the compensation medium,
showing that the viewing angle is significantly improved by the
addition of CLC to the cell.  The presently disclosed LCD using
homogeneous negative birefringence film allows a simple effective
method to improve the NW TN LCDs.  Through numerical calculation, the
optical thickness of the compensation film for the present device
should be between -0.27&mu.m % le ( n sub 'e' - n sub 'o' ) 'x d' le
-0.5&mu.m, where
 n  sub o    and   n sub e are the ordinary and extraordinary indices
of refraction of the compensation film, and d is film thi...