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Bistability Lifetime in Cholesteric Displays

IP.com Disclosure Number: IPCOM000005927D
Publication Date: 2001-Nov-15
Document File: 2 page(s) / 24K

Publishing Venue

The IP.com Prior Art Database

Abstract

The stability lifetime of the color reflective planar texture as well as the focal-conic transparent texture in a cholesteric display can be adjusted to affect optical and other performance features of a display cell. In cases were video or rapid paging rates are of necessity, the performance of the display may be improved by sacrifice of the stability lifetime in favor or faster or brighter response.

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Bistability Lifetime in Cholesteric Displays

ABSTRACT

The stability lifetime of the color reflective planar texture as well as the focal-conic transparent texture in a cholesteric display can be adjusted to affect optical and other performance features of a display cell.  In cases were video or rapid paging rates are of necessity, the performance of the display may be improved by sacrifice of the stability lifetime in favor or faster or brighter response.

INTRODUCTION

Cholesteric displays are attractive for use on handheld and portable devices because they consume unusually low levels of power.  This is primarily because of the bistability of the cholesteric textures used in displaying the image.  The color reflective planar texture and the transparent focal conic texture can be stable over a sufficiently long period of time such that an image can be addressed on a high resolution matrix display and the image remain on the display after the power is removed.  Normally, cholesteric displays are manufactured so that an image can remain on a display a year or longer without noticeable degradation.  Even the gray levels can be stable such that a display pixel which has a combination of planar and focal conic with maintain that particular combination and hence level of reflectivity over an indefinite period of time.

The lifetime of the focal conic and the planar state can however be adjusted such that a display may be bistable only over a short period of time; say 100 msec.  This may acceptable in an application where video is being portrayed or even in cases where the display is paged over short time intervals.

STABILITY CONTROL

The most common means of controlling the stability are by treatment of the alignment surfaces of the display substrate or by introduction of polymer networks in combination with a particular surface treatment [1,2].  With treatment of the substrate surface alone one can readily control the stability of the focal conic state [1,3].  With the use of polymer networks, one can control the stability of both the planar and focal-conic textures.  Extreme examples of the latter are the normal and reverse modes [4] where the polymers are used t...