Method and apparatus for driving reflective bistable cholestric displays
AssigneeThe Hong Kong University of Science and Technology
InventorsHoi-Sing Kwok, Fei-Hong Yu, Qing-Cheng Li, Wing-Chiu Yip
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Abstract
This invention provides a method and apparatus for driving bistable cholesteric liquid crystal displays. The method and apparatus provided a display in which all the pixels are initially driven to the P state. Selected pixels for the display are then driven to the FC state to provide the desired message. The state of the pixels is then maintained for a viewing period prior to any resetting of the display to the P state. The switching from the P state to the FC state allows fast addressing times and lower voltages to be used in driving the display.
Claims17
A bistable cholesteric liquid crystal display comprising:
- a plurality of pixels within said display;
- driving means to apply voltage to each pixel;
- and
- control means for controlling said driving means to supply a refresh pulse to said pixels to set all pixels to the reflective planar (P) state, to subsequently scan the plurality of pixels and supply a selection pulse to selected pixels to switch said selected pixels to the scattering/transparent focal conic (FC) state within about 0.5 ms to 2 ms without utilizing a surfactant within the bistable cholesteric liquid crystal display and to maintain said display for a period of time for viewing of the display.
A method of driving a bistable cholesteric liquid crystal display comprising the steps of:
- providing a refresh pulse to set all pixels to the reflective planar (P) state;
- switching selected pixels to provide the desired pattern to the scattering/transparent focal conic (FC) state within about 0.5 to 2 ms without utilizing a surfactant within the bistable cholesteric liquid crystal display;
- and
- holding said display for a suitable viewing period.
A bistable cholesteric liquid crystal display for switching pixels between a first stable state and a second stable state, comprising:
- a plurality of pixels;
- driving means for applying voltage to each pixel;
- and
- control means for controlling said driving means to supply a refresh pulse to said plurality of pixels to place said plurality of pixels in a first stable state, to subsequently scan the plurality of pixels and supply a selection pulse to selected pixels of said plurality of pixels in the first stable state to switch said selected pixels to a second bistable state within about 0.5 ms to 2 ms without utilizing a surfactant within the bistable cholesteric liquid crystal display to provide a desired pattern, and maintaining said display in the second bistable state for a period of time for viewing of the display;
- wherein said first stable state is the Planar (P) state and said second stable state is the Focal Conic (FC) state.
Dependencies are inferred from the claim text.