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As the construction of the second mirrored liquid crystal layer is very expensive, the compensation of developed devices has been accomplished with a solid foil ( about 2003 ). Such a foil is made from a polymer containing liquid crystalline side-groups.
Here, the demerit with respect to the DSTN ( double super-twisted nematic ) principle is that the optical compensation (≒ optical correction) will reach the complete condition only for one wavelength and one temperature.
Therefore, a slight coloration of the off-state is resulted from rise in ‘abnormal’ ambient temperatures.
