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Controlled Two-and Four-Domain Twisted Nematic Liquid Crystal Displays

IP.com Disclosure Number: IPCOM000101015D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Yang, K: AUTHOR

Abstract

It is well-known that, in twisted nematic (TN) (1) liquid crystal displays (LCDs), rubbed polyimide (PI) films coated on a transparent conducting electrodes may be used to align the direction of the nematic liquid crystal (LC) molecules such that the molecules twist 90o between the top and bottom cell substrates. When a transmissive TN LCD of this type is illuminated by a back light, the contrast ratio of the display depends on the viewing angle. In addition, a conventional single domain TN LCD has a narrow upper viewing zone and a wider lower viewing zone. The upper and lower viewing zones have a large contrast ratio, however, their grayscale characteristics are poor. In contrast, the left and right viewing zones are nearly symmetrical, with large contrast ratios and good grayscale characteristics.

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Controlled Two-and Four-Domain Twisted Nematic Liquid Crystal Displays

       It is well-known that, in twisted nematic (TN) (1) liquid
crystal displays (LCDs), rubbed polyimide (PI) films coated on a
transparent conducting electrodes may be used to align the direction
of the nematic liquid crystal (LC) molecules such that the molecules
twist 90o between the top and bottom cell substrates.  When a
transmissive TN LCD of this type is illuminated by a back light, the
contrast ratio of the display depends on the viewing angle.  In
addition, a conventional single domain TN LCD has a narrow upper
viewing zone and a wider lower viewing zone.  The upper and lower
viewing zones have a large contrast ratio, however, their grayscale
characteristics are poor.  In contrast, the left and right viewing
zones are nearly symmetrical, with large contrast ratios and good
grayscale characteristics.

      One substrate of a conventional single domain TN LCD, which
uses rubbed PI films as alignment layers, may be rubbed as
illustrated by the dashed arrow in Fig. 1(a).  The solid arrow of
Fig. 1(a) denotes the rubbing direction on the opposite substrate.
The liquid crystal molecules adjacent to the rubbed substrate surface
are aligned parallel to the rubbing direction.

      If each pixel of the TN LCD is made of 2 equal domains, the
display is called a two-domain TN LCD. Two-domain TN LCDs may be
constructed such that each display pixel consists of two domains
whose rubbing directions are chosen from any two schemes among Figs.
1(a) to 1(d).  The two-domain TN LCD showed improved grayscale
characteristics in the upper and lower viewing zones.  If each pixel
of the TN LCD is made of four equal domains whose rubbing directions
are shown in Figs.  1(a) to 1(d), respectively, the display is called
four-domain TN LCD.  The four viewing zones (left, right, up and
down) of a four-domain TN LCD should have contrast ratios and
grayscale characteristics which corre...