Search

In this study, we observed the color performance of an organic light-emitting diode (OLED) as functions of the optical lengths of the inorganic layers on the parameter space map in order to obtain the goal of increased color performance. To design the dominant wavelength and the bandwidth of the OLED, we employed the finite-difference time-domain method to calculate the optical characteristics of the light emitted from the emitting material layer. We only handled inorganic layers such as the cathode layer, the capping layer, and the indium-tin oxide layer in OLED layers to avoid changing the electro-optical characteristics of the light emerging from the organic layers. With this simple technique, we established the optimal conditions for the optical length of each layer without any intrusion into the organic layers. In this study, we demonstrated the parameter space map for a red OLED that exhibits a 24-nm bandwidth with a peak emission at wavelength λ = 618 nm. We verified the proposed parameter space method by experimentation and present the experimental results in this paper.

The application of a single-wall carbon-nanotube (SWCNT) and polyimide (PI) composite thin film on an indium tin-oxide (ITO) glass substrate, working as the command surface in a twisted nematic liquid crystal display (LCD), is described. SWCNTs were chopped and oxidized in a strong acid medium to make them more miscible in a polyimide solution. A film of this newly-developed PISWCNT composite was rubbed to determine the director direction for the LC molecules. The newlyfabricated command surface was examined using a laser beam profiler and atomic force microscopy. Sizes of shortened SWCNTs were characterized by using field-emission scanning electron microscopy (FE-SEM). Finally, small-sized test panels were fabricated from this composite-coated ITO glass, and their electro-optic performances were measured. Although the operating voltage to switch a cell was increased by around 41%, the switching speed was improved remarkably. The rise time of the test cells was found to be improved by around 10.12% and the decay time by around 29.77%. Thus, an overall improvement of around 16.12% in the total switching time was achieved. The change in the surface morphology of the newly-developed composite materials was found to be one of the factors responsible for the faster switching of the device. Detailed discussions are given in this report to explain the faster switching of the newly-developed twisted nematic liquid crystal display (TN-LCD). The device can be useful for practical applications.

The γ-curve represents the viewing angle characteristics of a liquid crystal (LC) cell in all gray levels, including the dark state. In this paper, we propose a optical configuration of a four-domain (4-D) twisted nematic (TN) LC cell for improving the γ-curve distortion in the oblique direction, without any deterioration in the optical property of a conventional 4-D TN cell. A positive A-plate and a negative A-plate are applied at the top and the bottom of the 4-D TN LC layer, respectively. The two A-films applied can be optimized at all viewing angles by calculating the polarization difference (Δ p ) as functions of the retardation and the optical axis of the films, so that the transmittance distortion in the middle gray scale can be compensated for in all viewing directions. As a result of a calculation of the gamma distortion index (GDI), the γ-curve can be improved by more than 70% in the off-axis at 0° and 180°, and by more than 50% in the off-axis at 90° and 270°.

In order to improve the image crosstalk for a film patterned retarder (FPR) of a linear polarizer type in a stereoscopic three dimensional (3D) display, we propose an optical structure with wideband and wide viewing angle characteristics and using only two half-wave retarders. This proposed half-wave retarder of the FPR 3D cell consists of a λ/2 biaxial film and a patterned λ/2 A-film. We calculated the phase retardation and confirmed the polarization states of the light passing through each film on the Poincare over all visible wavelengths by using the Stokes vector and the Muller matrix method. Then, we optimized the optical parameters of the two retardation films in the oblique direction by using the parameter space method as a function of the optical axis and the NZ parameter of the biaxial λ/2 film. Consequently, we verified that the left 3D crosstalk of the proposed FPR 3D cell could be improved by about 91.87% in the horizontal viewing direction and 97.22% in the vertical viewing direction. The right 3D crosstalk could almost maintain the crosstalk value of the conventional structure.

In this paper, we propose a numerical modeling method that can calculate the hydrodynamic behavior of a micro-sized charged particle in an electrophoretic cell. In order to simulate the electrokinetic characteristics of a particle in a real cell, we applied the electrostatic body force of the particle to the total dynamic interaction force and calculated the electrophoretic mobility so that we could calculate the dynamic response of the particle in a viscous fluid. We compared the calculated result with the experimental result of a horizontal switching electrophoretic cell for verification.