Herein, we report the enhancement of electro-optical performances of nanoparticle embedded liquid-crystal devices in the laser speckle pattern reduction, enhancement of viewing angle, and that of color gamut by doping the nano-particles(NPs) of PγCyclodixtrin-ZrO2 (Shiraishi lab) and Aerosil R-812(EVONIK) into the liquid crystal devices. This report will be done through updating of previous work [1-4] in particular giving physical modeling and simulations.
The doping of nanoparticles of PγCyD-ZrO2 and those hydrophobic SiO2 and TiO2 into brings tremendous changes in
their optical properties such as the reduction of birefringence, the creation of an optical homogenizing effect and the
enhancement of the performance of FSC-LCD that produces a large value of Luminance Efficiency; this paper reports
these novel optical effects in LCDs.
We have fabricated field sequential color (FSC)-LCDs using cells and modules of narrow-gap TN-LCDs with and
without doping the nanoparticles of PCyD-ZrO2 and AF-SiO2. It is shown that the FSC-LCD exhibits a high optical
efficiency of OE=4.5 that is defined as OE=[Luminance]/[W/m2]=(cd/W). This figure may provide us a good reference
or to clear the Energy Star Program Version 5-3 that issues a guideline: LCD with 50 inch on the diagonal consumes the
energy of 108W. Through this research it is claimed that our FSC=LCD may be a novel green digital signage.
Herein, we report that liquid crystal displays (LCDs) such as TN (twisted nematic)-mode, TB (tunable birefringence)-mode, VAN (vertically aligned nematic)-mode, BN (bent nematic)-mode,
and so forth, exhibit the reduction in the operating voltage and response times by doping the nanoparticles of inorganic substances such as MgO. These effects may be attributed to the modification of the physical properties of the liquid crystal host media in these LCD cells.
TN-LCDs fabricated by doping metal nanoparticles of such as Pd, Ag, Au, or Ag-Pd composite are shown to exhibit a frequency modulation electro-optic response with short response time of ms or sub-ms order. These devices are called FM-LCDs. The frequency range spreads from 40 Hz to 2 KHz around a dielectric relaxation frequency that increases with increasing the concentration of metal nanoparticles. This behavior is explained by the equivalent circuit model of heterogeneous dielectrics, for the first time, formulated by the present authors. Further, we discuss the origin of the fast response and the value of electrical conductivity of metal nanoparticles.
Electro-optic characteristics of a twisted nematic (TN) liquid crystal display (LCD) fabricated by doping Ag nanoparticles protected with NLC, 5CB (K-15, Merck) molecules has been investigated and it is shown that the device exhibits a unique electrooptic response characteristics that is sensitive to the high frequency component of the operating voltage together with the conventional root-mean-square response to the operating voltage. We call this device frequency modulation (FM) TN-LCD. The FM TN-LCD is switched by switching the frequency of the operating voltage while its amplitude is kept unchanged. As an example, by switching the frequency from 20Hz to 500Hz or 50Hz to 2kHz, and the switching is done with the time constant of several ms. This device shows a peculiar response to a burst AC square voltage waveforms, where the device exhibits bipolar response with the time constant of 500 ms and the envelope with the time constants shorter than those of an undoped TN-LCD by from 30% to 80%. The mechanism of the FM-TN-LCD is investigated through the study of its dielectric properties.
Defect free polymer-stabilized (PS-)V-mode FLCDs and intrinsic half (H-)V-mode FLCDs have been fabricated; they exhibit high contrast ratio over 700:1 and high reliability for a temperature cycling test by using specially developed polyimide alignment materials, RN-1411 series, from Nissan Chem. Ind., and also by adopting special alignment technique such as appropriate rubbing technique, photoalignment, and ion beam irradiation techniques and also particularly developed polymer-stabilization technique. These FLCDs are shown to be useful for implementing a field sequential type full color (FS-FC) LCDs due to their fast response with the response time of τ = 100μs ~ 500μs that is 10 to 100 times faster that those of LCDs using NLCs. We have developed several prototype models of FS-FC LCDs having VGA specifications that exhibit good performance for displaying fast moving video rate images with wide color gamut.
The effect of the photoalignment on the electrooptic characteristics of polymer stabilized ferroelectric liquid crystal displays (FLCDs) exhibiting V-shaped switching and those of FLCDs exhibiting half-V switching are reported and discussed. Photoalignment technique and hybrid alignment, which is done by combining photoalignment and rubbing, are shown to be useful for fabricating zig-zag defect-free FLCDs and improving the electrooptic characteristics of FLCDs-SSFLCDs, V-F-LCDs, and H-V-FLCDs- especially in the reduction of operation voltage.
A zig-zag defect free ferroelectric liquid crystal display exhibiting fast response speed, high contrast ratio, monostability with grayscale capability has been fabricated by using an especially developed polyimide alignment films and by adopting polymer stabilization with a mesogenic side- chain polymer. Some electrooptic performance of this display as a field sequential type color LCD are described and demonstrated.
The photopolymer materials of poly(vinyl cinnamate) (PVCi) and polyimides showing homeotropic liquid crystal (LC) alignment have been used to control LC alignment on these films using linearly-polarized (LP)- UV exposure, and the LC alignment mechanism including pretilt angle generation on the films has been discussed. In the case of PVCi, an important contribution of non-dimerized side chains of PVCi molecules to the LC alignment is pointed out. On the other hand, LC alignment on homeotropically alignment polymer films exposed to LP-UV light is shown to be determined through the interaction of LC with alkyl branches attached to the polymer. It is also shown that the photo-alignment method using these photopolymer materials are very promising technique for the fabrication of some attractive LCD modes such as in-plane switching and vertically-aligned display modes, and an example of the application of the photo-alignment method to the fabrication of in-plane switching device is presented.
TN-LCDs having multidomain subpixels have been fabricated using photoalignment. These TN-LCDs exhibit a homogeneous and wide viewing angle. This paper places an emphasis on four domain TN-LCD called super multidomain (SMD). The SMD- TN-LCD exhibits the maximum performance among other multidomain TN-LCDs which is shown in terms of computer simulation and experimental measurements done by the author's group. A non-rubbing technique is required for SMD; we also show that photoalignment is useful for fabricating SMD-TN-LCD. Some performance of an SMD-TN-LCD are demonstrated.
All kinds of LCDs are generally consisted of planar liquid crystal media, which are sandwiched between glass or plastic sheets. In this paper, the LC molecular conformations and their surface alignments in LCDs are systematically introduced, and the methods of LC surface alignment and their mechanisms are discussed. Furthermore the relationship between the EO performance of LCDs, such as TN, STN, Ch-N phase change, FLC, and PD-LCDs and the surface LC alignment is discussed.
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