Browse Prior Art Database

Optimized Driving Method for Contrast in Thin Film Transistor Liquid Crystal Display

IP.com Disclosure Number: IPCOM000114181D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 65K

Publishing Venue

IBM

Related People

Kimura, Y: AUTHOR [+3]

Abstract

Disclosed is an optimized driving method for contrast in Thin Film Transistor Liquid Crystal Display (TFT LCD). In gray scale errors due to vertical viewing angle dependence of the Twisted Nematic LCD is an important problem. Fig. 1 shows an example of the vertical viewing angle dependence of the TFT LCD. L0 to L5 are gray scales. As shown in this Figure, the contrast depends on the viewing angle and gray scales.

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Optimized Driving Method for Contrast in Thin Film Transistor Liquid
Crystal Display

      Disclosed is an optimized driving method for contrast in Thin
Film Transistor Liquid Crystal Display (TFT LCD).  In gray scale
errors due to vertical viewing angle dependence of the Twisted
Nematic LCD is an important problem.  Fig. 1 shows an example of the
vertical viewing angle dependence of the TFT LCD.  L0 to L5 are gray
scales.  As shown in this Figure, the contrast depends on the viewing
angle and gray scales.

      Fig. 2 shows an example of the viewing position.  If an
operator adjusts the contrast at screen position (a), the gray scale
error occurs at position (b).  To correct the gray scale error,
common or data voltage which corresponds to the viewing
characteristics of the LCD supplies to the common or data electrode
(data driver).

      Figs. 3a and 3b show the block diagram of the LCD module.  Fig.
4 shows an example of the circuit diagram.  Fig. 5 shows two examples
of the drive voltage characteristics.  In this Figure, sawtooth
voltage supplies to the common or data electrode which synchronizes
with vertical sync.  signal.  The supply voltage changes line by
line.

      Fig. 6a shows an application for this drive method.  Optimum
voltage changes by viewpoint of operator.  Operator can change the
waveform of the sawtooth generator to adjust the volume or turn
on/off the switch.  In case of Fig. 6b, angle sensor senses the
position and w...