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Browse Prior Art Database

Twisted Nematic Liquid Crystal Display for Gray Scale Application

IP.com Disclosure Number: IPCOM000121675D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Takano, H: AUTHOR [+2]

Abstract

Disclosed is a twisted nematic liquid crystal display (TN LCD), of which the commonly used viewing direction is set up to be the direction which does not provide good contrast ratio but rather good gray scale recognition.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 88% of the total text.

Twisted Nematic Liquid Crystal Display for Gray Scale Application

      Disclosed is a twisted nematic liquid crystal display (TN
LCD), of which the commonly used viewing direction is set up to be
the direction which does not provide good contrast ratio but rather
good gray scale recognition.

      TN LCD has a helical molecular structure and shows an optical
activity.  When a low voltage is applied parallel to the helical
axis, the helical structure of the liquid crystal molecules becomes
deformed and optical activity disappears.  The disappearance of the
optical activity depends on viewing direction.  Usually, in the
bi-level TN LCD, the commonly used viewing direction is set up to be
the direction in which we can obtain maximum contrast ratio; in other
words, in which maximum disappearance of the optical activity occurs.
But, in gray scale TN LCD, it becomes known that we cannot recognize
gray scales well from the direction in which we can obtain maximum
contrast ratio.

      The disclosed TN LCD provides better gray scale legibility by
setting up use of the direction opposite to the direction which
provides maximum contrast ratio.

      There are two optical modes in normally white TN LCD. They are
an extraordinary ray-dominant mode (abbreviated as e-mode) and an
ordinary ray-dominant mode (abbreviated as o-mode).

      The figures show polar viewing angle dependence of 8-level
transmittance with human eye correction.  The usual viewing zone
...