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Pixel and Rubbing Design for 90º and Low Twist Two-Domain Twisted Nematic Liquid Crystal Display to Eliminate the Undesirable Disclination Lines using Pixel Fringe Field

IP.com Disclosure Number: IPCOM000106766D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

John, RA: AUTHOR [+3]

Abstract

In a 90º or a low twist two-domain TN cell fabricated by the multiple-rubbing method, the undesirable disclination lines may appear in addition to the unavoidable disclination line located at the boundary of two designed domains. These undesirable disclination lines will cause the reduction of the optical contrast ratio of the panel if it is operated in a normally white mode.

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Pixel and Rubbing Design for 90º  and Low Twist Two-Domain Twisted Nematic Liquid Crystal Display to Eliminate the Undesirable Disclination Lines using Pixel Fringe Field

      In a 90º  or a low twist two-domain TN cell fabricated
by the multiple-rubbing method, the undesirable disclination lines
may appear in addition to the unavoidable disclination line located
at the boundary of two designed domains.  These undesirable
disclination lines will cause the reduction of the optical contrast
ratio of the panel if it is operated in a normally white mode.

However, use of black matrix to block out the undesirable
disclination lines will sacrifice the pixel aperture ratio.  In this
disclosure, the special designs for the pixel domain division and
rubbing directions of the 90º  and low twist two-domain TN are
disclosed to eliminate the undesirable disclination lines without
suffering from the reduction of the pixel aperture ratio.

      The basic principle for the design of the pixel domain division
and the rubbing directions is to arrange the liquid crystal molecules
in each domain to tilt in the direction which follows the pixel
fringe field direction.  More specifically, the left-handed twist
cell is used for an illustration.  Four designs are shown in Fig. 1.
We assume the common electrode substrate is closer to the viewer.  In
Figs. 1a and 1b, the TFT substrate uses higher pretilt alignment
agent and receives two rubbings.  The common electrode (color filter)
substrate, which uses l...