Positive Mode Heilmeier Cells

The geometry of Heilmeier cells was discussed in Sec. 3.4.8. Using a liquid crystal mixture of negative dielectric anisotropy mixed with pleochroic dye initially in ho-meotropic geometry, we can make a posi- 

To get the best results one requires unidirectional homogeneous alignment of the 

A dye of negative dichroism can be mixed into a liquid crystal mixture of positive dielectric anisotropy and put in a cell having unidirectional homogeneous alignment [13-16,52,53]. A single polarizer is oriented in front of the layer, with its transmission axis parallel to the rubbing direction of the adjacent cell. The cell does not absorb in the quiescent state, as the transition moment of 

Starting orientation A Aa Theoretical contrast ratio Sign of the contrast 

The contrast ratio is related to high voltages (V V, ) and the use of polarized light. In planar cells the E vector is parallel to n. In homeotropic cells the E vector agrees with n after the dielectric reorientation. 

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