In order to confirm the function of MTN model in our LCOS microdisplay device, we made the MTN test cell, in which low substrate is also glass instead of silicon. Since a standard commercial-like liquid crystal cell with low index glass( with an index close to 1.52) plate is to be investigated by a guided model technique to unravel the director profile through the cell, the low index improved fully leaky guided model(IFLGM) technique are chosen. At higher applied voltages (in our study U≥5.0 V(rms), the voltage-dependent reflectance can not be distinguished. In this range of the applied voltage, the electric fields create tiny difference in the distribution of the director only near the substrates and waveguide signals are just sensitive to this difference. Fitting the data in reflection by using the modeling-program based upon multilayer optical theory together with continuum theory gives the information about the pre-tilt and twist of the director as well as the parameters of different optical layers. We found that the pre-tilt angle on the top substrate is smaller 1° than that on the bottom in the best fit, this suggests that the ITO and the aluminum coatings have different effects on the alignment layers.
An in-plane switching π-twisted liquid crystal device with fast response speed is proposed. Electric filed is applied in the plane of the substrates, unlike a conventional π-cell. Two quarter wavelength films are used to obtain black/white mode. The electro-optical characteristics and switching behavior of this mode are studied by using two-dimensional model. A good dark state is obtained when the electrode is black. Numerical results show that the proposed mode has excellent viewing angle and fast response speed.
Based upon the Ericksen-Leslie hydrodynamic equations, we studied an inverse twisted nematic liquid crystal cell, in which the liquid crystal is untwisted in the field-off state and twisted in the field-on state. The time evolution of director configuration and velocity of flow was obtained by computer simulation. An abnormal director profile that caused by the backflow appeared after switching on the holding voltage. We also compared the optical transmittance of the inverse twisted nematic liquid crystal cell having backflow effect with that without considering backflow effect.
An in-plane switching mode super twisted nematic liquid crystal device with the wide viewing angle characteristics and fast response speed is proposed. Electric filed is applied in the plane of the substrates, unlike a conventional super twisted nematic (STN) mode. The compensation films were used in this mode for obtaining the black/white mode with very small color shift. Compared with the normal in-plane-switching mode and in-plane-switching mode twist nematic configuration, its response speed is improved four times on not only the rise time but the decay time. With the compensation film, the excellent viewing angle, weak color shift can assimilate with that of normal IPS mode. The fast response speed will be useful in designing the video-response liquid crystal displays.
Color shift, viewing angle character and response speed for the in-plane switching super-twisted nematic cell are analyzed. The viewing angle depends on the change of the effective birefringence dΔn, the response time depends on the structure of liquid crystal display. The very wide viewing angle, fast resopnse times and low color shift are shown at any gray scales in this new mode. Potential applications for large screen refelctive displays are foreseeable.
A novel model of ELectrically Controlled Birefringence (ECB) liquid crystal display was studied by detailed numerical simulation. The toothed surfaces were formed on the two substrates and the two substrates were interlaced with each other. The optimized mode with cell gap 3.4μm was determined by theoretical analysis. By using extend Jones matrix method, we have shown that the narrow viewing angle in horizontal direction, less than ±10°. The viewing angle characteristics of the novel model are compaed wiht those of usual ECB.
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