Abstract— A 1M‐pixel full‐color projection display with a very simple optical system using a conventional overhead projector has been developed. This display uses the nematic‐cholesteric phase‐transition liquid‐crystal display and a micro‐color‐filter. Moreover, the micro‐color‐filter can be placed outside the liquid‐crystal panel. This simple configuration provides a high‐performance low‐cost color electronic overhead projector. This projection display uses a 9M‐pixel nematic‐cholesteric phase‐transition black‐and‐white liquid‐crystal panel to enable gray shades by spatial dither, resulting in a full‐color projection display. A 12:1 contrast ratio and 2.2‐ms line‐addressing time is achieved.
Liquid crystals using nematic-cholesteric phase change can be used in dot matrix displays of more than 500 scanning lines. High driving voltage requirements, such as 20 V, and the transient disappearance of written images on the way to memory after writing are two drawbacks of this display. We are developing a storage-type liquid crystal display, which can be driven by C-MOS LSIs, that overcomes these drawbacks. Lowering the viscosity of the liquid crystal mixture containing nematic and cholesteric materials was investigated to see if a lower driving voltage could be used. To shorten the transient disappearance time, dispersion of the helical pitch distribution, which storage-type liquid crystal shows, has been studied. Reducing the driving voltage enables us to drive the storage-type liquid crystal display with a C-MOS LSI. Since the problem of transient disappearance has been solved, this type of panel can be used for large-sized displays.
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