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STORAGE CAPACITORS IN A TFT ADDRESSED LIQUID CRYSTAL DISPLAY PANEL

IP.com Disclosure Number: IPCOM000025311D
Original Publication Date: 1984-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 85K

Publishing Venue

Xerox Disclosure Journal

Abstract

A prior art thin film transistor (TFTJ 10 addressed liquid crystal displav (LCD) panel 19 needs an extra storage capacitor 12 in each display element to achieve 100 percent duty cycle as shown in Figure 1. The purpose of the storage caoacitor is to store the video information charged on the liquid crystal electrode 18 durine the line addressing time for the whole frame period. For a commonly used refreshing rate of 60 Hz, the RC time constant of the storage capacitor with the TFT in the "off" condition has to be greater than 17 milliseconds. At preynt, the "off" resistance of the TFT can be made to be greater than 3 x 10 ohms. Therefore, the storage capacitor of each display element should be greater than 6 PF*

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XEROX DISCLOSURE JOURNAL

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STORAGE CAPACITORS IN A TFT ADDRESSED LIQUID CRYSTAL DISPLAY -. PANEL ._ __

Fang-Chen Luo

SOURCE SOURCE

Proposed Classification US. C1. 350/160
Int. Cl. G02b 27/00

GATE

GATE

GATE

BUS

FIG. 2

FIG. 3

Volume 9 Number 4 July/August 1984 26 1

    FIG. I (PRIOR ART) SOURCE AND DATA BUS

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STORAGE CAPACITORS IN A TFT ADDRESSED LIOUID CRYSTAL DISPLAY PANEL (Cont'd)

A prior art thin film transistor (TFTJ 10 addressed liquid crystal displav (LCD) panel 19 needs an extra storage capacitor 12 in each display element to achieve 100 percent duty cycle as shown in Figure 1. The purpose of the storage caoacitor is to store the video information charged on the liquid crystal electrode 18 durine the line addressing time for the whole frame period. For a commonly used refreshing rate of 60 Hz, the RC time constant of the storage capacitor with the TFT in the "off" condition has to be greater than 17 milliseconds. At preynt, the "off" resistance of the TFT can be made to be greater than 3 x 10 ohms. Therefore, the storage capacitor of each display element should be greater than 6 PF*

As shown in Figure 1, the prior art storage capacitor 12 is between the drain pad 14 of TFT 10 and the next gate bus bar 17. This involves several extra fabrication steps to fabricate the capacitors and also sacrifices the size of the display electrode.

In Figure 2, the capacitance between the drain pads 24 of a TFT-LCD circuit and the ground plane 23 al...