Hyeokjin Lee

11.1: Invited Paper: The World's First Blue Phase Liquid Crystal Display

Recently, the display of liquid crystal having the blue phase have been studied more intensively because it has many merits such as wide viewing angle without compensation films, very fast switching response time, and no need for the alignment layer and the rubbing process. First, we confirmed the feasibility of the blue phase liquid crystal display by means of polymer stabilization in the test cell. Even though we could get a wide temperature range that shows the blue phase, there were still problems such as the high operation voltage, hysteresis so on. In 2008, by developing and applying new technologies for improving these characteristics, we successfully fabricated a new kind of the liquid crystal display using the blue phase for the first time in the world.

Ultrafast switching of randomly-aligned nematic liquid crystals.

We propose an ultrafast nematic liquid crystal (LC) device without alignment layers, where both the dark and bright states can be realized by applying an electric field. A vertical electric field is applied to vertically align the LCs for the dark state, whereas an in-plane electric field is applied to homogeneously align the LCs for the bright state. We achieved a total response time of less than 3 ms in the proposed device. This device may contribute, not only to a significant improvement of the switching speed in liquid crystal devices, but also to the simplification of the device fabrication by the omission of the alignment layer coating and the rubbing process.

Low Voltage and High Transmittance Polymer-Stabilized Blue-Phase Liquid Crystal Device by Combined In-Plane and Oblique Electric Field along the Horizontal Direction

We propose a polymer-stabilized blue-phase liquid crystal (PS-BPLC) device with high transmittance and low driving voltage by designing the electrode structure. The electrodes are comprised with two interdigitated bottom pixel electrodes with opposite polarities and a top common electrode with 0 V, which is placed in the middle of the two bottom electrodes. Since these electrode structures could generate a strong horizontal electric field and induce a high Kerr effect, we could realize a lower driving voltage (30 V) and higher transmittance characteristics (20%) than those of conventional PS-BPLC cells with an in-plane switching electrode structure.

Maximization of an Electric Field Penetrating an Optically Isotropic Phase Liquid Crystal for Low Operating Voltage Display

Liquid crystal displays (LCDs) correlated with polymer-stabilized optically isotropic state LC mixtures show relatively low light efficiency and very high operating voltage when the device is structured by interdigitated electrodes which generate in-plane electric fields. This is because the horizontal field intensity is not strong enough and half of the field is wasted by penetrating the substrate and the Kerr constant of the mixture is not high enough. We propose an electrode structure which can absolutely diminish the operating voltage while keeping the transmittance by generating in-plane electric fields penetrating the LC layer twice stronger than that of the conventional one.