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1. US5606437 - Direct drive split pixel structure for active matrix liquid crystal displays

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[ EN ]
I claim:
1. A wide viewing angle liquid crystal display comprising:
a plurality of first conductors oriented in a first direction;
a plurality of second conductors oriented substantially parallel to the first direction;
a plurality of third conductors oriented in a second direction substantially perpendicular to the first direction; and
a plurality of pixel elements, each pixel element comprising:
a first pixel sub-element having a color associated therewith, the first pixel sub-element being coupled to one of the plurality of first conductors and to one of the plurality of third conductors, wherein the one of the plurality of first conductors and the one of the plurality of third conductors are used to drive the first pixel sub-element with a first drive voltage to a first gray scale intensity;
a second pixel sub-element having the color associated therewith, the second pixel sub-element being positioned adjacent to the first pixel sub-element, the second pixel sub-element being coupled to one of the plurality of second conductors and to the one of the plurality of third conductors, wherein the one of the plurality of second conductors and the one of the plurality of third conductors are used to drive the second pixel sub-element with a second drive voltage generated separately from the first drive voltage to a second gray scale intensity independent of the first gray scale intensity, each pixel element having an average gray scale intensity which is a function of gray scale intensities of the first and second pixel sub-elements; and
the first drive voltage is any of a plurality of selectable drive voltages corresponding to a plurality of selectable gray scale intensities.
2. The wide viewing angle liquid crystal display of claim 1 wherein the second drive voltage is any of the plurality of selectable drive voltages corresponding to the plurality of selectable gray scale intensities.
3. The liquid crystal display of claim 1 wherein the one of the plurality of first conductors is coupled to the first pixel sub-element but not to the second pixel sub-element, and wherein the one of the plurality of second conductors is coupled to the second pixel sub-element but not to the first pixel sub-element so that the first and second pixel sub-elements can be driven to selected gray scale intensities independently of one another.
4. The liquid crystal display of claim 3 wherein the first pixel sub-element is coupled to the one of the plurality of first conductors and to the one of the plurality of third conductors through a first thin film transistor, and wherein the second pixel sub-element is coupled to the one of the plurality of second conductors and to the one of the plurality of third conductors through a second thin film transistor.
5. The liquid crystal display of claim 4 wherein the plurality of first conductors and the plurality of second conductors are column conductors and wherein the plurality of third conductors are row conductors, the liquid crystal display having approximately twice as many column conductors as row conductors.
6. The liquid crystal display of claim 5 wherein the column conductors are substantially straight conductors which extend substantially parallel to one another.
7. The liquid crystal display of claim 6 wherein the plurality of pixel elements form a brickwall structure having rows of pixel elements, pixel elements in each row having a repeating pattern of colors associated therewith, the repeating pattern of colors in each row being offset from the repeating pattern of colors in adjacent rows such that each column conductors is coupled to a plurality of pixel sub-elements having a first color and being positioned on a first side of the column conductor, and is coupled to a plurality of pixel sub-elements having a second color and being positioned on a second side of the column conductor.
8. The liquid crystal display of claim 1 wherein the first gray scale intensity is essentially uniform over a wide range of viewing angles.
9. The liquid crystal display of claim 1 wherein the one of the plurality of first conductors and the one of the plurality of third conductors are used to periodically drive the first pixel sub-element with the second drive voltage to the second gray scale intensity while the one of the plurality of second conductors and the one of the plurality of third conductors are used to periodically drive the second pixel sub-element with the first drive voltage to the first gray scale intensity.
10. A method of achieving gray scale in a liquid crystal display over wide viewing angles, the liquid crystal display having a plurality of pixel elements, each of the plurality of pixel elements having first and second individually driveable adjacent sub-elements, an average gray scale intensity of each particular pixel element being a function of gray scale intensities of the particular pixel element's first and second adjacent sub-elements, the method comprising:
determining a desired average gray scale intensity for a first pixel element having a first color associated therewith;
determining a first drive voltage as a function of the desired average gray scale intensity for the first pixel element, the first drive voltage is any of a plurality of selectable drive voltages corresponding to a plurality of selectable gray scale intensities;
determining a second drive voltage as a function of the desired average gray scale intensity for the first pixel element;
providing the first drive voltage to a first sub-element of the first pixel element in order to drive the first sub-element to a first fray scale intensity, the first sub-element having the first color associated therewith; and
providing the second drive voltage to a second sub-element of the first pixel element in order to drive the second sub-element to a second gray scale intensity, the second sub-element having the first color associated therewith, the first and second gray scale intensities being selected such that an average gray scale intensity of the first pixel element is approximately equal to the desired average gray scale intensity.
11. The method of claim 10 wherein the first drive voltage is below a threshold voltage such that the first gray scale intensity is substantially viewing angle independent so that a viewing angle dependence of the first pixel element having the desired average gray scale intensity is minimized.
12. The method of claim 10 wherein the first drive voltage is above a saturation voltage such that the first gray scale intensity is substantially viewing angle independent so that a viewing angle dependence of the first pixel element having the desired average gray scale intensity is minimized.
13. The method of claim 12 wherein a voltage value of the second drive voltage can be increased without substantially increasing the first drive voltage above the saturation voltage.
14. The method of claim 10 wherein the first drive voltage has a voltage value which results in the first pixel sub-element having the first gray scale intensity and being substantially viewing angle independent so that a viewing angle dependence of the first pixel element having the desired average gray scale intensity is minimized.
15. A method of achieving gray scale in a liquid crystal display over wide viewing angles, the liquid crystal display having a plurality of pixel elements, each of the plurality of pixel elements having first and second individually driveable adjacent sub-elements, an average gray scale intensity of each particular pixel element being a function of gray scale intensities of the particular pixel element's first and second adjacent sub-elements the method comprising:
determining a desired average gray scale intensity for a first pixel element having a first color associated therewith:
determining a first drive voltage as a function of the desired average gray stale intensity for the first pixel element:
determining a second drive voltage as a function of the desired average gray scale intensity for the first pixel element:
providing the first drive voltage to a first sub-element of the first pixel element in order to drive the first sub-element to a first gray scale intensity, the first sub-element having the first color associated therewith: and
providing the second drive voltage to a second sub-element of the first pixel element in order to drive the second sub-element to a second gray scale intensity, the second sub-element having the first color associated therewith, the first and second gray scale intensities being selected such that an average gray scale intensity of the first pixel element is approximately equal to the desired average gray scale intensity;
periodically reversing the first and second gray scale intensities by providing the first drive voltage to the second sub-element of the first pixel element in order to drive the second sub-element to the first gray scale intensity, and by providing the second drive voltage to the first sub-element of the first pixel element in order to drive the first sub-element to the second gray scale intensity, wherein periodically reversing the first and second gray scale intensities results in a time averaged gray scale intensity for each of the first and second sub-elements which is approximately equal to the desired average gray scale intensity for the first pixel element.
16. A wide viewing angle liquid crystal display comprising:
a first pixel element having a first color associated therewith, the first pixel element comprising:
a first pixel sub-element having the first color associated therewith; and
a second pixel sub-element adjacent the first pixel sub-element and having the first color associated therewith;
means for driving the first pixel sub-element at a first drive voltage to obtain a first gray scale intensity from the first pixel sub-element;
means for driving the second pixel sub-element at a second drive voltage to obtain a second gray scale intensity from the second pixel sub-element, an average gray scale intensity of the first pixel element being a function of the first and second gray scale intensities, wherein a value of the second drive voltage is selectively chosen independent of a value of the first drive voltage is
the first drive voltage is chosen such that the first sub-element having the first gray scale intensity is substantially viewing angle independent:
the second drive voltage is chosen such that the second sub-element having the second gray scale intensity is substantially viewing angle independent:
the second drive voltage is substantially equal to the first drive voltage and the second gray scale intensity is substantially equal to the first gray scale intensity.