Quasi-bookshelf layer structure

Quasi-bookshelf layer structure with stripe domains)... 

Fig. 6.1.4 Changes in texture induced by AC-field treatment, (a) Texture I. Initial virgin texture with chevron layer structure and zigzag defects, (b) Textures II. A rooftop texture is observed after the application of an AC field of medium strength, (c) Texture HI. A quasi-bookshelf layer structure with stripe domains is observed after the apphcation of a strong AC field.

Y. Sato, T. Tknaka. H. Kobayaahi. K. Aoki. R Wsianabe, R Ihkeshiia. Y. Ouchi. R Thk ezoc. and A. Pukuda. High quality ferroelectric liquid crystal display with quasi-bookshelf layer structure, Jpa. J. AppL Pkys. 28.L483 (1989). 

The chevron structure and zig-zag defects were shown to disappear if a low-frequency electric field of sufficient amplitude is applied to an FLC cell [152-154]. The voltage required for the reorientation decreases with increasing spontaneous polarization. The texture appearing resembles the book-shelf geometry of smectic layers perpendicular to the substrates. It has minimum response time, maximum transmission difference between both stable states, and a relatively uniform viewing area. Therefore this texture, referred to as quasi-bookshelf geometry [152], seems to be very promising for display applications. 

The quasi-bookshelf smectic layer structure is realized and the twisted state of the director alignment is inherently avoided. Hence the relatively high contrast ratio of 20-30 is easily obtained. 

If zigzag defects already exisL they can be removed by an adequate AC electric field treatment which causes a change from the chevron structure to a slightly bent layer structure [24,25] which is termed "quasi-bookshelf." Alternatively, a quasi-bookshelf alignment has btwn obtained for spe dasses of FLC materials [26]. To summarize, there are at present four different optical structures which avoid the occuneooe of zigzag defects and are considered for applkation ... 

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