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Browse Prior Art Database

LIQUID CRYSTALLINE DISPLAY ILLUMINATION SYSTEM

IP.com Disclosure Number: IPCOM000023264D
Original Publication Date: 1977-Apr-30
Included in the Prior Art Database: 2004-Mar-29
Document File: 2 page(s) / 226K

Publishing Venue

Xerox Disclosure Journal

Abstract

Electro-optic cells employing the cholesteric to nematic phase transition in a liquid crystalline layer and placed between orthogonal linear polarizers are provided with larger viewing angles and minimized birefringerice effects by use of the pre-sented proposed illumination system.

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XEROX DISCLOSURE JOURNAL

LIQUID CRYSTALLINE DISPLAY ILLUM- Proposed Classification
INATION SYSTEM U.S. Cl. 350/16OLC
Jerome N. Harris mt. Cl. G02b 5/23

Electro-optic cells employing the cholesteric to nematic phase
transition in a liquid crystalline layer and placed between
orthogonal linear polarizers are provided with larger viewing
angles and minimized birefringerice effects by use of the pre-
sented proposed illumination system.

A fluorescent lamp is constructed with a clear aperture in the
lamp phosphor layer across the length of the lamp. This lamp is
then placed slightly above and to the rear of the electro-optic
cell and is rotated about its central, longitudinal axis until
uniform brightness is observed at the front of the electro-
optic cell. A black light absorbing material is placed below
and slightly in front of the lamp so that it is positioned
directly behind the display area. This material absorbs rather
than reflects light and blocks ambient light from areas behind
the display.

With this proposal, the light brightness falloff horizontally
is the cosine function of a uniform diffuser. Thus, wide hori-
zontal viewing angles are achieved. No effects due to bire-
fringence are observed because there is rio light coming from
directly behind the panel. All observed brightness is due to
scattering in cholesteric areas of the cell. Therefore, a
cholesteric to nematic phase transition display is provided
with few angular viewing problems.

Volume 2 Number 2 March/April 1977 67...