Browse Prior Art Database

Thin Film Transistor for Gray Scale LCD

IP.com Disclosure Number: IPCOM000100937D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Kaida, Y: AUTHOR [+2]

Abstract

Disclosed is a TFT (Thin Film Transistor) structure for LCD (Liquid Crystal Display) which is able to display a halftone level. By using this structure, gray scale can be displayed and the extension of viewing angle is as wide as that of binary level LCD.

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Thin Film Transistor for Gray Scale LCD

       Disclosed is a TFT (Thin Film Transistor) structure for
LCD (Liquid Crystal Display) which is able to display a halftone
level.  By using this structure, gray scale can be displayed and the
extension of viewing angle is as wide as that of binary level LCD.

      Fig. 1 shows a schematic rendition of this TFT structure.
Figs.  2 and 3 show plane views of the first and the second
transparent electrodes, respectively.  These transparent electrodes
are, for example, ITO (Indium Tin Oxide).  With this structure,
different size capacitances are fabricated serially to the
capacitance of the liquid crystal layer.  The equivalent circuit is
shown in Fig. 4. Each area from A1 to An has a different threshold
voltage on the V-T curve, as shown in Fig. 5.  By applying voltage Vk
to this dot, the area from A1 to Ak shows black, whereas, on the
other hand, the area from Ak+1 to An shows white. Therefore, by
changing the applied voltage, n level gray scale can be realized.

      The conventional gray scale method TN (Twisted Nematic) LCD has
the problem of narrow viewing angle, because each gray scale level
has different viewing angle characteristics.  However, by using this
method every gray scale level has the same viewing angle.  It is an
useful advantage especially for a large LCD.