Technology Papers
A brief abstract of the paper is provided under the title. Should you wish more, simply clicking on the title will open the full paper in a new window.
A brief abstract of the paper is provided under the title. Should you wish more, simply clicking on the title will open the full paper in a new window.
Characterization of the Helical-Axis Distribution in Reflective Cholesteric LCDs
A unique technique for characterizing the orientation distribution of the helical axis in the planar state of reflective cholesteric display has been developed. It is used to study domain structure and to optimize display geometry for use in specific applications.
Bistable Reflective Cholesteric Displays
With the arrival of the information age, electronic displays are playing an ever increasing role as the interface between information processing machine and human beings. Computer monitors, television sets, public information displays are just a few examples. The trend of electronic displays is towards thinner, lighter and more energy-efficient packages owing to the huge demand in portable application such as notebook and palmtop personal computers, personal digital assistants (PDAs), pagers, portable fax machines, portable information terminals, etc. This is why flat-panel displays, including liquid crystal displays (LCDs), plasma display panels, electroluminescence displays and field emission displays are expanding their applications.
High-Performance Dynamic Drive Scheme for Bistable Reflective Cholesteric Displays
We report a high performance dynamic drive scheme for bitable reflective cholesteric displays suitable for use in electronic books and newspapers. The drive scheme consists of preparation, pre-selection, selection and evolution phases in altered pipeline sequences to minimize the visual response to the black bar. The pre-selection phase makes it possible to shorten the selection phase to 0.2 ms.
Polymer Walls In Higher-Polymer-Content Bistable Reflective
We have formed polymer walls in a high polymer content, bistable reflective cholesteric display using photo-polymerization phase separation on glass and plastic substrates. The polymer walls serve to adhere the substrates and increase the brightness and contrast of the display. The results of microscopic observations, SEM analysis and electro-optic characterization will be presented.
Recent advances In Bistable Reflective Cholesteric Displays: Relaxation from Homeotropic Texture in Pulsed Cells
We examined the relaxation of cholesteric liquid crystals from homeotropic to planar texture using spectral measurements of electrically pulsed cells with varying field-off times. This technique allows us to follow shifts in the reflectivity peak over short time intervals. Our results confirm a transient planar texture with longer pitch than the final planar texture. The resulting shift in wavelength can be utilized to produce a white on black reflective display.
Novel Bistable Reflective Cholesteric LCD with Excellent Contrast Ratio and Fast Response Time
A new type of bistable reflective cholesteric liquid crystal display is reported for the first time. The texture and the relaxation process is very different from the other type of the reflective cholesteric displays reported previously. The contrast ration of the cholesteric display is about 2.5 times higher than the regular cholesteric displays made with the same liquid crystal materials. A model to explain the unique textures of the display is presented as well.
Cholesteric liquid-crystals displays illuminated by diffuse and partially diffuse light
We report on the photometric and colorimetric properties of surface and polymer network stabilized reflective cholesteric displays. Both diffuse and partially diffuse illumination are used, the latter being an experimental approach to emulating typical room light conditions. It is shows that addition of polymer increases the field of view while decreasing angular dependence of the color quantities: hue, chroma, and lightness. Total luminance and contrast ration, however, are also decreased. Therefore, it is concluded that optimum polymer concentration is dependent of the viewing geometry. Luminance and contrast ration of the surface stabilized cells exceeded that of polymer stabilized cell when viewed in a geometry void of specular reflection. Colorimetric quantities in surface stabilized cells are less sensitive to illumination geometry. This suggests that for displays in which specular reflection has been suppressed, surface treatment represents the best method of stabilization. If the viewing angle allows specular reflection, polymer stabilization yields the largest luminance and contrast ratio. This behavior is explained in terms of angular distribution of helical axes due to present of the stabilizer
Reflective Cholesteric Liquid Crystal Displays
Guided by an earlier but similar experiment using smectic liquid crystal, the thought was to see if the polymer network would be twisted by the cholesteric material. Surprisingly, it was discovered that the polymer had a most unusual effect on the cholesteric phase: Stabilizing one of its optically clear states while maintaining the stability of a color reflective state. It was possible to switch the materials back and forth between these two stages states by applying a low-or a high-voltage pulse to a cell containing the materials. A second surprise was the observation that the reflected color did not appreciably with the angle of view of the cell, a charter is no exception from the early history of research with cholesteric materials. An, finally, a third surprise was the discovery that polymers were not needed at all to create the displays’ features the surface of the cell could do the same thing. It was obvious from these discoveries that the cholesteric liquid-crystal material was a good candidate for a reflective flat-panel display technology.