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TWISTED NEMATIC DISPLAY WITH IMPROVED MULTIPLEX ABILITY UTILIZING SIMPLE ALIGNMENT TECHNIQUE

IP.com Disclosure Number: IPCOM000024496D
Original Publication Date: 1980-Oct-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 104K

Publishing Venue

Xerox Disclosure Journal

Abstract

Existing twisted nematic displays operated in the reflective mode are limited to 4 - 8 levels of multiplexing. Furthermore, the region of good angular viewing is limited. An improved system is proposed which utilizes collimated rear illumination and a front diffuser. In addition, a simplified liquid crystal alignment technique may be used if the collimated illumination is brought in at an optimal angle.

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XEROX DISCLOSURE JOURNAL

TWISTED NEMATIC DISPLAY WITH IM- PROVED MULTIPLEX ABILITY UTILIZING SIMPLE ALIGNMENT TECHNIQUE
Gary A. Dir

Proposed Classification
U.S. Cl. 430/20 Int. Cl. C09k 3/34

Existing twisted nematic displays operated in the reflective mode are limited to 4 - 8 levels of multiplexing. Furthermore, the region of good angular viewing is limited. An improved system is proposed which utilizes collimated rear illumination and a front diffuser. In addition, a simplified liquid crystal alignment technique may be used if the collimated illumination is brought in at an optimal angle.

The number of lines which can be multiplexed in a liquid crystal display is dependent on the sharpness of the electro-optical transfer curve (light transmission versus voltage). Since the sharpness of this curve depends on the angle the rays of light pass through the liquid crystal, multiplexability can be improved by illuminating the display at the angle where the transfer curve is sharpest.

Since the liquid crystal panel does not scatter the incident light, a front diffuser is used to diffuse the light in a broad lobe allowing favorable wide angle viewing features. Front diffusers which have been found effective include ground glass and emulsion types.

The basic arrangement is shown in the figure. A collimated beam of light 11 is formed by placing a point source 13 such as a zirconium arc at the back focus of a lens 15. Light then floods the back of the panel 17 at the angle (a) which is chosen to give maximum multiplexability. The liquid crystal 19, operated in the twisted nematic mode, acts simply as a shutter either blocking or passing incident illumination dependent upon its state of electrical excitation. Light passing through the liquid crystal is, in turn, scattered by a front diffuser 21 chosen for its viewing features.

Volume 5 Number 5 September/Oc...