SPONTANEOUS TRANSITION FROM CHEVRON TO STRIPED TEXTURE OF A PLANAR SMECTIC-C-ASTERISK LIQUID-CRYSTAL

We observed a spontaneous transition from a vertical chevron texture to a striped texture (striped "bookshelf" texture) in a surface-stabilized film of ferroelectric liquid crystal mixture (ZLI 4237-000, from E. Merck). The transition takes place gradually, at temperatures more than 20-degrees-C below the smectic-A-smectic-C* transition. The layers in the stripe texture are perpendicular to the plate, but in successive stripes, the orientation of the layer normal alternates by +/- 23-degrees. The polarization is perpendicular to the film and alternates between up and down, while the director orientation is in plane and alternates by +/- 5-degrees. The width of the stripes was typically 50-mu-m for samples of about 5-mu-m thickness. The area of the kink interfaces between the stripes is accordingly an order of magnitude smaller than in chevron textures, which energetically favors the stripe texture. The formation of this texture is slow because it requires sliding of the layers along the surface. The observed transition can be of importance for display technology because it may enable one to obtain a uniform bookshelf texture.