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Novel Two-Domain Twisted Nematic Structures and their Fabrication Methods to Prevent Reverse Twist and Image Sticking

IP.com Disclosure Number: IPCOM000118701D
Original Publication Date: 1997-May-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 117K

Publishing Venue

IBM

Related People

Lien, S-CA: AUTHOR

Abstract

Disclosed are two new structures of Two-Domain Twisted Nematic (TDTN) liquid crystal panels and their fabrication methods.

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Novel Two-Domain Twisted Nematic Structures and their Fabrication
Methods to Prevent Reverse Twist and Image Sticking

                         Fig. 1 Structure 1

      Disclosed are two new structures of Two-Domain Twisted Nematic
(TDTN) liquid crystal panels and their fabrication methods.  The
first structure is shown in Fig. 1, where the left-handed twist is
shown for  illustration.  (The left-handed chiral agent is added to
the Liquid Crystal (LC) before it is filled to the panel.)  The
right-handed twist  can also be used for this structure by a proper
modification of the alignment directions.  The dashed lines represent
the edges of a pixel  electrode on the bottom substrate and the solid
lines represent the boundary of the electrode on the top substrate
for the corresponding pixel.  Please notice that the common electrode
on the top substrate for a Thin Film Transistor/Liquid Crystal
Display (TFT/LCD) panel is a  continuous Indium Tin Oxide (ITO).  The
dashed arrows represent alignment  direction of the bottom substrate.
The solid arrows represent the alignment direction of the top
substrate.  The single-headed arrow,
'        or         ', represents alignment with non-zero pretilt
angle.  The pretilt is in the direction as if the substrate is rubbed
in the direction indicated in the single-headed arrow direction even
though the alignment method other than rubbing method may be used.
The
double-headed arrow, '       or         ', represents alignment with
a zero or near zero pretilt angle.  The alignment configuration of
this structure can be achieved by rubbing first and then followed by
the polarized light irradiation through a photo-mask.  In detail, the
entire substrate is rubbed first in the direction of the
single-headed arrow.  The rubbing process creates a non-zero pretilt
angle.  The substrate is then exposed to a polarized light through a
photo-mask which  covers area I but does not cover area II of each
pixel for both bottom  and top substrates.  The polarization
direction of the polarized light  is perpendicular to the rubbing
direction.  The polarized light produces  an alignment whose
direction is perpendicular to the polarization direction of the light
and the pretilt angle is zero.  Thus, the alignment direction in area
II stays the same as that created by the rubbing process but the
pretilt angle is reset to zero.  However, the alignment direction and
pretilt angle in area I is not affected by the polarized light
irradiation since area I is covered by the photo-mask.  With this
structure, when a voltage is applied to the panel,  the liquid
crystals in the middle plane of the upper half pixel tilt upward and
the liquid crystals in the middle plane of the lower half pixel tilt
downward.  Thus, each pixel is divided into two domains.

      The second structure is shown in Fig. 2.  The convention of the
lines and arrows are the same...