Liquid crystal display (LCD) have been widely used, because of their advantages of low power consumption, compactness, and flatness. However, the properties of alignment layers have not been understood, especially from the point of their chemical structure. In this paper, the required properties of alignment layer for active matrix LCDs was reviewed, and the author's study on the alignment layers, which were soluble in common organic solvents, was reported from the point of their pretilt angle, voltage holding ratio and image sticking properties. Finally, problems and trends of alignment layer technology were briefly described.

View full abstract

We have investigated the generation of the high pretilted angles for nematic liquid crystal (NLC), 5CB on rubbed polyimide (PI) films containing trifluoromethyl moieties. The rubbed P[ films were characterized with ESCA instrument as a function of rubbing strength (RS). It is shown that the pretilt angles decrease with decreasing the surface atomic concentration F/C (%) induced by the rubbing that results in the increase of surface energy. From this results,we suggested that the high pretilted angles for NLC (5CB) aligned on this pI film is obtained by surface morphology of special polymer. Also, we have studied that the polar anchoring energies for NLC (5CB) by using "high-electric-field technique" on weakly rubbed PI films. It is shown that the polar anchoring energies is strongly related to surface order parameter on rubbed PI films.

View full abstract

To Measure the pretilt angle in a liquid crystal cell, the crystal rotation method is commonly used because it is very precise and measurements can be obtained rapidly. However when a liquid crystal cell with insufficient uniformity of the cell gap is used, a significant error occurs due to a shift in the measurement point. This shift is caused by refraction of the glass plate during rotation of the cell. In this paper, we estimate the magnitude of this error theoretically and experimentally and propose a new method by which an accurate value can be obtained even if the cell gap is not uniform.

View full abstract

Polymer layers can cause memory alignment for nematic liquid crystals. We describe an experimental method to characterize this effect. We studied the temperature dependence of the memory alignment. We also investigated the influence of the time span during which the memory alignment is generated. The observed phenomenons can be explained by a reasonable adsorption-desorption mechanism.

View full abstract

An insulating layer disposed on a transparent driving electrode is required for an actual liquid crystal display (LCD), in order to prevent, short circuiting between a segment. and a column electrodes. However, the high resistivity of the insulating layer causes a static electric charge and deforms a wave of the driving voltage, which deteriorates uniformity and contrast ratio. In order to solve these problems, a conductive insulating layer is developed: a conductive material is doped, and then the effect of the conductive insulating layer is proved. The conductive insulating layer enhances the discharge of the electricity and the uniformity of contrast ratio. And also its optimum condition of resistivity protects the LCD from short circuiting and can maintain the lower voltage driving condition of STN-LCD.

View full abstract

TN LCDs have angular dependence and their graylevel order is reversed. To suppress this reversal, a complemenatry TN structure with two domains is proposed and its optical characteristic is simulated. This simulated result shows this graylevel order reversal is suppressed within 40 degrees in up and down directions. Fabricated complementary TN result agrees with this simulated results. Images on 4.3"-diagonal complementary TN LCD will be showed.

View full abstract

The new columnar plasma chemical vapor deposition (CP-CVD) method, which can process a large quantity of the substrates for one batch, has been applied to deposit SiN_X. films. The characteristics of the deposited SiN_X films depend on the region where the reaction has occured. The reaction in the reactive region is much different from that in the supplied region. The films deposited in the reactive region are excel-lent as a insulator. In the supplied region, the quality of the films is deterionated because of an outbreak of the Si cluster.

View full abstract