Vertically aligned nematic mode liquid crystal display having large tilt angles and high contrast

Abstract

A reflective liquid crystal on silicon (LCOS) display comprises a transparent substrate, a reflective substrate, and liquid crystal fluid between the substrates. The LCOS display further comprises a matrix of pixels, arranged in a plurality, of rows and columns, wherein an intersection of a row and a column defines a position of a pixel in the matrix. The LCOS display has tilt angles sufficient to overcome disclinations due to fringe fields, and, at the same time, achieves high contrast. The surface azimuthal direction of the molecules of the liquid crystal fluid is either substantially parallel or perpendicular to the direction of polarization of incoming incident linearly polarized light. Light leakage is minimal because the effective birefringence as seen by the incoming incident linearly polarized light is substantially zero and does not depend on the pretilt of the molecules of the liquid crystal fluid. Between the transparent substrate and the reflective substrate, the twist of the molecules of the liquid crystal fluid may vary from about 0 degrees to about 90 degrees when in the "OFF" state.

Description

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 60 / 450,370, entitled "Method to Eliminate the Disclination Defects Due to Fringe Fields in Vertically Aligned Nematic Reflective LC Displays Without Hurting the Display Contrast" by Hemasiri Vithana, filed Feb. 26, 2003, and is incorporated herein by reference for all purposes.[0002] The present invention relates generally to liquid crystal displays (LCDs), and more particularly to reflective liquid crystal on silicon (LCOS) displays.BACKGROUND OF THE FIELD OF TECHNOLOGY[0003] Liquid crystal display technology has reduced the size of displays from full screen sizes to minidisplays of less than 1.3 inches diagonal measurement, to microdisplays that require a magnification system. Microdisplays may be manufactured using semiconductor integrated circuit (IC) dynamic random access memory (DRAM) process technologies, e.g., liquid crystal on silicon (LCOS). The LCOS microdisplays consist of a silicon...

AI Technical Summary

Problems solved by technology

Although this pretilt angle is large enough to prevent reverse tilt domains in the display, it is not possible to overcome the defects that occur due to fringe fields between neighboring pixels.

Ultimately this will create defects at the pixel boundaries, usually known as disclinations.

However, the dark state of a VAN mode liquid crystal display with a pretilt angle of this magnitude has a significant amount of light leakage through the crossed polarizers and the light contrast it can achieve is not that high.

Therefore, the inherent property of VAN displays, the very dark "OFF" state, cannot be fully achieved.

Therefore, there is an effective birefringence as seen by the incoming incident light and it increases with increasing pretilt angle, hence the amount of light leakage.

However, this configuration cannot be applied to practical applications because the "ON" state is not bright due to the same reason explained above.

However, this does not work well for the BLUE channel giving rise to a reasonable amount of light leakage.

Such retarders with good uniformity are difficult to find and not easily available commercially.

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