By Kohki Takatoh
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The utility of this equation was confirmed by demonstration that the effects of cylinder rotation speed and number of times a substrate is rubbed are independent of the anchoring strength of a ferroelectric LC as shown in Fig. 22 . From this result, the linear relationship between l and the anchoring strength was confirmed. Aerle et al. defined the rubbing strength as the rubbing density Rd described as , Rd ¼ ½ðCw þ vÞ=N ð2:3Þ 28 Masaki Hasegawa 10 Rotation speed n was changed Cumulative number of rubbings N was changed 9 8 da [µm] 7 6 5 4 3 2 1 0 0 50 100 Rubbing strength parameter L [cm] Fig.
Limited viewing angle caused by unidirectional alignment The electro-optical characteristics of a single domain TN LC display have a strong viewing angle dependency, because the director of the LC rotates in the same plane over the entire area of each pixel. To improve this, a multi-domain 46 Masaki Hasegawa Fig. 38 Relation between azimuthal anchoring energy and actual twist angle of a 90 TN cell. technology was developed, in which each pixel is divided into two or four areas, and the LC in each area rotates in a different direction when the electric field is applied.
In other cases, it increases with increase in rubbing strength and decreases after showing a peak . Nishikawa et al. calculated the molecular conformation, and explained these phenomena by using the model shown in Fig. 28 . Paek et al. considered that the relationship between the pretilt angle of the LC and the rubbing strength is caused by increasing the interaction between the LC and the alignment material due to the increase in the surface polarity caused by rubbing, or the decrease in the average tilt angle of the polymer caused by changes of the surface wave structure .