Contrast Heilmeier displays

With increasing dye concentration c, the contrast ratio of the Heilmeier display increases and its transmission decreases... 

As predicted from theory, the order parameter has a dramatic impact on the contrast ratio (Fig. 11). The order parameter of the dye is the only parameter that increases both the contrast ratio and the transmission simultaneously. Figure 11 shows that for a good Heilmeier display the dichroic order parameter should be as high as possible (preferably >0.75). 

Figure 10. Effect of cell gap on the threshold characteristic and contrast of a Heilmeier display. The trans-mittances of cells with 5, 8, and 11 im cell gaps are 23.6%, 20.0%, and 16.0%, respectively. Operating voltage, 10 V.

The contrast ratio of a Heilmeier display is highly dependent on the polarization effi-... 

Table 2. Contrast ratio and percent transmission of Heilmeier, dye doped TN, and TN displays versus viewing angle [16].

Recently, Ong [126] proposed a Heilmei-er display having two asymmetric cells. This display has a high contrast and wide viewing angles, but low transmission. One can also use two separate Heilmeier cells with different dyes to make a composite cell, and by controlling voltage differently a set of colors can be obtained. Two cells with different dyes and one polarizer, can also be used. 

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