Excellent bistability was demonstrated in a ferroelectric liquid crystal electrooptic device prepared using polyimide Langmuir-Blodgett films for the orientation of the liquid crystals without performing rubbing.
The degree of work done on polyimide films in the rubbing process with a nylon fabric was detected and evaluated in terms of induced birefringence. Strong and weak rubbing (effecting two extremes) gave rise to the optical retardation of 1 degree and 0.1 degree, respectively, with a resolution of 0.1 degree. Generation of a pretilt angle of up to 10 degrees (even up to 30 degrees) for nematic liquid crystals was achieved by performing weak rubbing in a specially synthesized polyimide which was successfully used to fabricate supertwisted nematic liquid crystal displays. Fairly good bistability in a ferroelectric liquid crystal device was obtained by weak rubbing.
Enhancement of bistability and response speed in a surface-stabilized ferroelectric liquid crystal (SSFLC) electrooptic device was realized by doping a charge-transfer complex (CTC) into an FLC host. These characteristics were found to be effective for pulsed voltage waveforms whose duration exceeded several 100 µs depending on LC materials and aligning polymer films. The polarity of the electrooptic response to the pulsed waveforms was shown to be inverted in comparison with an undoped device, depending on the polar nature of polyimide substrates.
Fe/Ti multilayered films composed of Fe and Ti layers with various thickness ( dFe of 10 ∼ 1000 A and dTi of 10 ∼ 200 A ) have been prepared at Ar gas pressure of 2 mTorr by two pairs of Facing Targets Sputtering apparatus which can deposit very thin and continuous films on plasma-free substrates. The total thickness of Fe layers was 1000 A in all of the specimen films.The periodic microstructure due to compositional modulation was clearly observed not only in the low angle region of X-ray diffraction diagrams but also in the Auger electron spectroscopic depth profile.With decreasing dFe from 1000 to 20 A, the diffraction intensity of (110) plane in the Fe bcc phase lowered for dTi of 10∼200 A and its interplanar spacing ( d-spacing ) increased for dTi above 50A. This diffraction peak disappeared with further decreasing d below 15 A. At dFe around 25 A, a different peak appeared at the angle slightly lower than that of Fe(110) peak. The diffraction intensity of (002) plane in the Ti hcp phase increased with decreasing dFe. However, its d-spacing depended little on the dFe and took the same value as that of bulk Ti except for very small dTi.The net saturation magnetization of Fe layers in all of the specimen films decreased gradually with decreasing dFe from 1000 to 50 A, decreased abruptly with further decreasing dFe and became nearly zero at dFe below 15A.The films annealed at 200 and 400 °C showed obscure periodic microstructure and had larger d-spacing of ∝ −Fe(110) and smaller saturation magnetization than those of the as-deposited ones.
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