Dynamic drive method and apparatus for a bistable liquid crystal display
First Claim
1. A method of addressing a bistable chiral nematic liquid crystal material disposed between electrodes arranged on opposed sides of said liquid crystal and adapted to selectively apply an electric field through said liquid crystal material, said method comprising the steps of energizing said electrodes to establish a preparation voltage across said liquid crystal during a preparation phase, thereafter energizing said electrodes to establish a selection voltage across said liquid crystal during a selection phase for selecting a final display state for said liquid crystal, next energizing said electrodes to establish an evolution voltage across said liquid crystal during an evolution phase, and thereafter permitting said liquid crystal to exhibit the final display state.
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Accused Products
Abstract
A flat-panel liquid crystal display. The display includes a flat sheet of bistable chiral nematic liquid crystal material activated by a drive circuit that individually controls the display state of multiple picture elements at a refresh rate 1000 scan lines per second. The driver circuitry activates the liquid crystal domains into homeotropic states over a relatively long activation period and then, during a short (˜1 msec.) selection period, either keeps the domains in a homeotropic state or initiate a transition to the transient twisted planar state. The drivers then activate the domains in an evolution phase to provide either focal conic or twisted planar end states across the two-dimensional array of picture elements.
260 Citations
25 Claims
- 1. A method of addressing a bistable chiral nematic liquid crystal material disposed between electrodes arranged on opposed sides of said liquid crystal and adapted to selectively apply an electric field through said liquid crystal material, said method comprising the steps of energizing said electrodes to establish a preparation voltage across said liquid crystal during a preparation phase, thereafter energizing said electrodes to establish a selection voltage across said liquid crystal during a selection phase for selecting a final display state for said liquid crystal, next energizing said electrodes to establish an evolution voltage across said liquid crystal during an evolution phase, and thereafter permitting said liquid crystal to exhibit the final display state.
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13. A method for displaying information comprising the steps of:
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a) providing a layer of bistable liquid crystal material and arranging electrodes on opposed sides of the liquid crystal material to form an array of display elements; b) coupling the electrodes to a drive circuit for energizing the electrodes to selectively activate the display elements of the array to one of a first and a second final display; and c) addressing selected display elements of the array by sequentially energizing the liquid crystal material at a selected display element location with a preparation signal during a preparation phase, reducing the preparation signal to a selection signal for pre-disposing the liquid crystal material to later attain a desired final display state, changing the signal across the display element to an evolution signal during an evolution phase, and then allowing the display element to exhibit the desired final display state which is different than the state of the liquid crystal material during application of said selection signal. - View Dependent Claims (14, 15, 16, 17)
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18. A display apparatus comprising:
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a) a layer of bistable chiral nematic liquid crystal material; b) multiple electrodes spaced on opposite sides of the liquid crystal layer for applying selected activation voltages across multiple picture elements of the liquid crystal layer; and c) control electronics for sequentially setting a display state of multiple picture elements of the liquid crystal layer comprising circuitry for; i) applying a preparation signal across a selected picture element during a preparation phase; ii) applying a selection signal across said selected picture element during a selection phase to select a predetermined final display state; and iii) applying an evolution signal across said selected picture element during an evolution phase. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification