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Capacitive Discharge Thermal Address of Matrix-Addressed Smectic Liquid Crystal Display

IP.com Disclosure Number: IPCOM000045908D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Onton, A: AUTHOR

Abstract

A capacitive discharge method for addressing a matrix-addressed smectic liquid crystal display is described.

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Capacitive Discharge Thermal Address of Matrix-Addressed Smectic Liquid Crystal Display

A capacitive discharge method for addressing a matrix-addressed smectic liquid crystal display is described.

The display apparatus is addressed by driving a selected line to thermally alter the state of the liquid crystal. One shortcoming of this type of display has been the large amount of instantaneous power required to address the display.

The capacitive discharge method of addressing has the advantage of accumulating energy and storing it electronically until enough is available to thermally address one line. The apparatus comprises a power supply 10 of arbitrary voltage connected to charge capacitor C to a suitable voltage V/0/. A switching means 12 is provided which can trigger at an adjustable predetermined voltage V/0/ to discharge the capacitor C through a horizontal select switch 14 and the selected horizontal display line 16 of resistance R and to produce a gate pulse on line 18 to address the vertical lines. In this circuit, the thermal addressing of the line occurs as a result of a decaying current pulse as the charge on capacitor C decays through the resistance R. The voltage waveform on capacitor C is shown in Fig. 2.

By the use of this addressing method, the heat is driven into the liquid crystal more efficiently since the heat transfer is driven by a temperature gradient. As shown in Fig. 3, for the capacitive discharge drive, the maximum temperature of the li...