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PITCH ADJUSTMENT OF FERROELECTRIC LIQUID CRYSTALS

IP.com Disclosure Number: IPCOM000025831D
Original Publication Date: 1988-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 78K

Publishing Venue

Xerox Disclosure Journal

Abstract

The pitch of a ferroelectric liquid crystal is an important parameter in device performance. In devices with the book-shelf configuration, for example, where the helix of the ferroelectric liquid crystal is unwound and the smectic planes are substantially perpendicular to the substrates, the cell spacing required to achieve helix unwinding is dependent upon the pitch of the material. Cell spacing must be less than the pitch of the helix for unwinding to occur. Thus, if the pitch of the material is 3pm, the spacing must be less than 3pm, around 2pm or below. This rule puts severe constraints on materials and cell spacings for use in devices with the book-shelf geometry. Adjustment of the pitch of the helix is thus a useful tool to have in device applications.

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XEROX DISCLOSURE JOURNAL

PITCH ADJUSTMENT OF FERROELECTRIC LIQUID C R Y STA LS
Joseph J. Wysocki
Sui-Kong Hark
V. Joseph Hull

Proposed Classification

US. C1.350/160 Int. C1. G02f 1/28

The pitch of a ferroelectric liquid crystal is an important parameter in device performance. In devices with the book-shelf configuration, for example, where the helix of the ferroelectric liquid crystal is unwound and the smectic planes are substantially perpendicular to the substrates, the cell spacing required to achieve helix unwinding is dependent upon the pitch of the material. Cell spacing must be less than the pitch of the helix for unwinding to occur. Thus, if the pitch of the material is 3pm, the spacing must be less than 3pm, around 2pm or below. This rule puts severe constraints on materials and cell spacings for use in devices with the book-shelf geometry. Adjustment of the pitch of the helix is thus a useful tool to have in device applications.

A customary way of adjusting the pitch of these smectic materials is to mix appropriate proportions of right and left handed smectic materials. With the proper proportions, the pitch can be varied uniformly to values of infinity, i.e. the helix has been unwound. A proposed method of adjusting the pitch, which is unusual in the sense that heretofore only mixtures of similar (smectic) materials have been used to achieve pitch changes, is the use of nematic and cholestericc materials in this combination. Nematic materials have an e...