Shock stability of FLC displays

One of the intrinsic problems for the practical application of FLC displays is the low mechanical stability of the molecular orientations. The initial molecular orientations in an FLC material are easily destroyed by the application of mechanical pressure and/or mechanical shock. The materials do not return to their initial states, unlike molecular orientations in nematic liquid crystals, which are also disturbed by mechanical pressure and/or shock but usually return to their initial states. The low stability of FLC devices under exposure to shock is attributed to the presence of the smectic layer structure. The molecular orientation of the smectic phases is highly ordered in comparison with that of the nematic phase. 

15 An example of pictures of the 15 passive matrix, full colour FLC display reported by Koden [27]. 

The processes of damage imder exposure to mechanical shock differ according to whether the shock consists of a continuous pressure or a hammer-style shock [30, 31]. 

The typical process of damage resulting from a continuous pressure is illustrated in Fig. 6.1.16 [31]. When relatively little pressure is applied, zigzag defects appear, but the material recovers to its initial state after the pressure is removed. However, with a higher pressure, the initial state is transformed to a damaged texture (Fig. 6.1.16(d)) and the material does not recover. This phenomenon is caused by a reduction in the cell gap and the resultant flow of material from the compressed region. 

Various approaches to realizing a high degree of stability under exposure to shock have been investigated. Adhesive spacers have been proposed as a way of 

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