Modifying electrooptics of orthoconic antiferroelectric liquid crystal cells by manufacturing procedures

Abstract

Orthoconic antiferroelectric liquid crystals (AFLCs) having 45° tilt angle have been proposed to overcome the problem of reduced contrast usually exhibited by regular antiferroelectric displays. However, the pitch of the helix induced by chirality is customarily short in existing orthoconic materials, making it difficult to achieve surface stabilized configurations when the material’s pitch is smaller than the cell thickness.In this work, the influence of different manufacturing procedures on the electrooptical behaviour of orthoconic AFLCs is studied. Using the same orthoconic AFLC mixture, aligning surfaces and manufacturing protocol, we have observed two dissimilar responses, true orthoconic behaviour, and orthoconic V-shape response. The electrooptical response depends ultimately on the rubbing strategy adopted in either case.

Synthesis and properties of high tilted antiferroelectric esters with partially fluorinated alkoxyalkoxy terminal chains

“…The mixture W-232 with an optical tilt saturates at 40 degree (at 35°C) and shows better electrooptical performance than the fully orthoconic mixture W-193B [2,8] exhibiting a very short pitch with often avoided correct alignment, resulting in asymmetry in an electrooptical response and shows unsatisfactory dynamic behaviour and exceedingly high voltage levels. However, the electrooptical properties, measured in a cell filled with W-232, exhibiting long pitch and high spontaneous polarization (Ps = 230 nCcm -2 ), show lower threshold and saturation voltage, fully symmetric hysteresis curve and more linear greyscale.…”

Comparative electrooptic study of new orthoconic liquid crystals with fluorinated alkoxy terminal chains

“…The main drawback of all measured materials for high−rate multiplexed schemes is their high switching voltage, more than 40 V. The new mixture W242 shows the best dynamic and static results among investi− gated OAFLCs mixtures. It also shows better electrooptical properties if compared with previously OAFLC mixture W193B [4,5]. This material has good electrooptical respon− se, the dynamic range of about DR (10-90) = 8 V and good relaxation time.…”

“…However, these exhibited a very short helical pitch at room temperature, usually less than 1 μm. In this case, surface stabilized struc− tures are only possible to achieve if the material is confined into very thin cells (~0.8 μm) [4,5] where n = 1-7 and m = 2-7.…”

Dielectric and switching properties of a highly tilted AFLC material (S)-(+)-4-(1-methylheptyloxycarbonyl)-2,3-difluorophenyl 4′-[3-(2,2,3,3,4,4,4-heptafluorobutoxy)prop-1-oxy]biphenyl-4-carboxylate

“…Switching time of AFLCDs also depends upon the kind of addressing scheme, and it may be accelerated by choosing the appropriate addressing system. [47,48] Figure 11 (b) shows to the variation of T S (which is the time for full width from the starting point of hump to maxima of peak of the hump). T S is known as electrical switching time.…”