| Although nematic liquid crystal has been applied widely, such as monitors of television and computer, its application has been limited in the area that needs high response speed. The response speed of ferroelectric liquid crystal is at least 100 times faster than nematic liquid crystal. It is a quite promising liquid crystal material in the optical fields. It is difficult to have a uniform alignment with no defects. The devices have poor thermal stability and mechanical stability. So its application was limited.The formation mechanism of"zigzag"shaped defects was analysed in this paper. The reason is that the bulk free energies of C1 state and C2 state are very approaching for ferroelectric liquid crystal with a phase sequence of I?N*?SmA?SmC*, and C1 state and C2 state optionally appeared depending on the pre-tilt angle of the orientation layer."Zigzag"shaped defects with the coexistence of C1 state and C2 state will appear if the pre-tilt angle is not uniform. The effect of the surface roughness of the orientation layer on the emergence probability of"zigzag"shaped defects was studied by experiments. The results indicated when the surface of orientation layer was much rougher, the alignment of ferroelectric liquid crystal with"zigzag"shaped defects appeared more easily. It was showed that the roughness will produce changes of local pre-tilt angle near the value of critical pre-tilt angle up and down. Using the ratio H/W to signify the roughness degree of orientation layer, where H represents height of the convex and W represents width of the convex bottom. It was found when H/W was less than 0.006 in the experiment, the uniform alignment without"zigzag"shaped defects could be realized.Ferroelectric liquid crystal was injected into the liquid crystal cell at isotropic phase according to the fabrication process of ferroelectric liquid crystal device, then stabilized at SmC * phase after three phase transitions by cooling. The cooling rate during the phase transition and thermodynamic equilibrium state before the phase transition are important effect factors on ferroelectric liquid crystal alignment. In order to obtain high-contrast ferroelectric liquid crystal devices, it was found by experiment that the cooling rates during the N* ? SmA phase transition and SmA? SmC* phase transition were to slow to 0.1°C/min, and holding 40 min at constant temprature before N*→SmA phase transition to form thermodynamic equilibrium state.Taking advantage of the parallel alignment characteristic of nematic liquid crystal, it is easy to obtain a uniform alignment of ferroelectric liquid crystal, by doping nematic liquid crystal with the same molecular length to ferroelectric liquid crystal molecule or shorter, but it has poor stability in environment with disturbance.In order to improve the thermal stability and the resisting performance for shock of ferroelectric liquid crystal devices,we doped a liquid crystal photosensitive monomer with the same molecular length to ferroelectric liquid crystal molecule or shorter into ferroelectric liquid crystal,then it was exposured in UV at SmC* phase. A side-chain polymer liquid crystal, whose main chains were distributed between the layers and side-chains were distributed parallel to ferroelectric liquid crystal molecules. It not only maintained the uniform alignment, but also greatly enhanced the resisting performance for shock. The stability problem of the uniform alignment was resolved. Comparing with Polymer network stabilized ferroelectric liquid crystal, devices fabricated by Polymer liquid crystal stabilized ferroelectric liquid crystal, have fast response, high driving contrast, no effect of wide fibers and no light leakage.The way of polymer liquid crystal stabilized ferroelectric liquid crystal is also suitable for ferroelectric liquid crystal with the phase sequence of I?N*?SmC* except for I?N*?SmA?SmC* . The problem of alignment was resolved. The divice obtained has driving contrast of 182:1 and fast response of 300μs.
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