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IMPROVED OPERATION OF FERRO-ELECTRIC LIQUID CRYSTAL DEVICES IN A VARYING TEMPERATURE AMBIENT

IP.com Disclosure Number: IPCOM000025765D
Original Publication Date: 1987-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 126K

Publishing Venue

Xerox Disclosure Journal

Abstract

Surface stabilized ferroelectric liquid crystals (FLC's) have high potential for use in displays, image bars, and shutters. Because these materials are not absorbing, these devices will probably incorporate a polarizer and analyzer, permanently attached to the device, the polarizer attached at an angle corres-ponding to one of the two surface stabilized states and the analyzer at 90 degrees to the polarizer. With FLC in this state, there is no light passing through the cell. When the FLC is activated, the material is switched to the other surface stabilized state which now allows light to pass through the device.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

IMPROVED OPERATION OF FERRO- Proposed Classification ELECTRIC LIQUID CRYSTAL DEVICES U.S. C1.350/331R
IN
A VARYING TEMPERATURE Int. C1. G02f 1/133 AMBIENT
Joseph J. Wysocki ,oo

80

60

CONTRAST RATIO (CR

TRANSMISSION (Ye)

40

20

\ \

And I h = 0.5

/

0 20 30 40 50

TEMPERATURE (*C)

DARK

FIG. I

Volume 12 Number 6 November/December 1987 269

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Page 2 of 4

IMPROVED OPERATION OF FERROELECTRIC LIQUID CRYSTAL DEVICES IN A VARYING TEMPERATURE AMBIENT (Cont'd)

100

80

60

1% CONTRAST RATIO (CR)

40

20

0 20

TEMPERTURE(<)

FlG. 2

     XEROX DISCLOSURE JOURNAL Volume 12 Number 6 November/December 1987

270

[This page contains 1 picture or other non-text object]

Page 3 of 4

IMPROVED OPERATION OF FERROELECTRIC LIQUID CRYSTAL DEVICES IN A VARYING TEMPERATURE AMBIENT (Cont'd)

Surface stabilized ferroelectric liquid crystals (FLC's) have high potential for use in displays, image bars, and shutters. Because these materials are not absorbing, these devices will probably incorporate a polarizer and analyzer, permanently attached to the device, the polarizer attached at an angle corres- ponding to one of the two surface stabilized states and the analyzer at 90 degrees to the polarizer. With FLC in this state, there is no light passing through the cell. When the FLC is activated, the material is switched to the other surface stabilized state which now allows light to pass through the device.

The transmission of light '7"' through the device is governed by Equation 1 below, in which 28 is the angle separating the surface stabilized states, A is the wavelength, An is the bi-refringence and "d" is the gap in the device. The parameter which is most temperature dependent is 8. As shown in Equation 2, 8 varies with temperature. Here, 80 is a constant of the LC, "t" is the temperature, "to" is the Curie temperature at which the material loses its ferroelectricity, and a is a constant, typically -0.35. A plot of transmission expected from Equations 1 and 2 for bot...