The Effect of Chemically Modified Multi-Walled Carbon Nanotubes on the Electro-Optical Properties of a Twisted Nematic Liquid Crystal Display Mode
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In this study, we have chemically modified multi-walled carbon nanotubes (MWNTs) with different side chains for better dispersion in liquid crystal solutions, and fabricated twisted nematic liquid crystal cells doped with such MWNT derivatives. The introduction of MWNT derivatives affects the alignment of LC molecules with or without external electric fields. Electro-optical property tests showed that the contrast ratio changed slightly with the sharp decrease in drive voltage, improving the drive ability of the twisted nematic liquid crystal display (TN-LCD) mode.Keywords:
Contrast ratio
Biaxial nematic
Thermotropic crystal
Biaxial nematic
Mesogen
Lyotropic
Columnar phase
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A twisted nematic liquid crystal is shown by theory and experiment to rotate incident plane-polarised light by π/2 only at specified wavelengths. At other wavelengths, elliptically polarised light is produced. This action determines the contrast ratio of some twisted nematic devices.
Contrast ratio
Biaxial nematic
Ray
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We have proposed a novel full-color reflective liquid crystal display (LCD) using a hybrid aligned LC cell, color filters of red, green and blue, a mirror electrode inside the cell and a light-diffusing film. In this paper, we describe a design concept for improving the contrast ratio of this reflective LCD. In addition, we propose an advanced reflective full-color LCD using a light-control film instead of a Gaussian-type light-diffusing film. This reflective LCD has a wide viewing angle, a high contrast ratio and a high resolution and is promising as a high-quality reflective full-color LCD for next-generation portable information systems.
Contrast ratio
Viewing angle
Full color
Color filter array
High contrast
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The formation of biaxial nematic phases in mixtures of surfactants and water is discussed. Emphasis is given to experimental data that confirm the existence of a biaxial nematic phase. Some new microscopic observations and birefringence measurements are reported. Biaxial nematic phases were observed in two systems that have, in addition, two uniaxial nematic phases. The general features of the phase transitions involving these nematic phases are theoretically analyzed on the basis of a Landau expansion. Specific relations for the order parameters are derived that compare favorably with the experimental results.
Biaxial nematic
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In recent years, liquid crystal displays (LCDs) are being increasingly used in various display products, such as cellular phones and televisions, leading to demands for higher image quality and lower power consumption. The contrast ratio of LCDs is, however, lower than that of emissive displays such as organic light-emitting diode ones. A novel algorithm for LCD backlight dimming to improve the contrast ratio of LCDs is proposed. Backlight luminance and a gamma conversion function are simultaneously optimized acording to input images by minimizing the sum of squared difference between the ideal gamma characteristic with an infinite contrast ratio and the LCD gamma characteristic with a finite contrast ratio. Furthermore, LCD prototypes that utilized the proposed algorithm were developed, and they had both a high contrast ratio and low power consumption.
Backlight
Contrast ratio
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In this work experimental and theoretical results will be used to show that under convenient conditions; appropriated geometry, well chosen boundary conditions, and suitable external fields, the elastic and dynamic behavior of a sample of a biaxial nematic liquid crystal can become similar to the one observed on usual uniaxial nematic liquid crystals. It is shown that this result can be used to determine the values of some combinations of the rheologic parameters of the biaxial phase.
Biaxial nematic
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We describe new topologies in the phase diagrams involving biaxial nematic liquid crystals. We find that a direct isotropic-biaxial nematic phase transition is possible. Our results show that three different biaxial nematic phases can occur. We outline how the novel phase diagrams could be detected experimentally.
Biaxial nematic
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Abstract Abstract In his classic paper on the elastic behaviour of nematic liquid crystals published in 1958, Sir Charles Frank hints at the existence of a nematic phase with biaxial symmetry in addition to the conventional nematic phase with its uniaxial symmetry. Little notice appears to have been taken of this intriguing suggestion until 1970 when Freiser presented a molecular theory of nematics formed from biaxial molecules. This predicted that such materials should exhibit isotropic, uniaxial nematic and biaxial nematic phases although for a certain critical biaxiality the system should pass directly from the isotropic phase to a biaxial nematic. Despite these clear predictions it was not until the late 1980s that the claims to have prepared compounds exhibiting a thermotropic biaxial nematic phase began to appear; these originated from the laboratories of Jaques Malthtte, S. Chandrasekhar and Klaus Praefcke. However, subsequent studies of some of the materials suggested that the nematic phases claimed to be biaxial were, in fact, uniaxial. Although the formation of real biaxial nematics is in doubt, computer simulators have produced biaxial nematic phases in keeping with the theoretical predictions. In addition, about 17 years ago Alfred Saupe had discovered a biaxial nematic phase formed by a lyotropic system.
Biaxial nematic
Thermotropic crystal
Lyotropic
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This paper presents a dual-view (DV) liquid crystal display (LCD) fabricated with a twisted nematic (TN) cell that has patterned electrodes on its substrates. The TN DV LCD effectively inhibits the bright state light leakage in the un-intended viewing direction, improving the contrast ratio of the DV LCD when the right and the left subpixels of the DV LCD are addressed simultaneously. In the preferred viewing direction, the TN DV LCD has a high contrast ratio of ~ 140:1.
Contrast ratio
Viewing angle
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Analytic expressions are obtained using the generalized geometrical-optics approximation for the field-off state optical field and transmission of the general double layer twisted nematic and supertwisted nematic liquid crystal displays with arbitrary display parameters. A variety of display characteristics can be obtained from such structures. In particular, the strong interference colors in the field-off state single layer supertwisted nematic displays can be completely removed in a double layer supertwisted nematic display; thus, a black or white off state is possible. For the double layer 90° twisted nematic, besides the complete black or white field-off state, it can also exhibit off state display performance similar to that for either the single layer 180° supertwisted nematic or the optical mode interference display.
Biaxial nematic
Double layer (biology)
Dark state
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