Liquid crystal display device and method of driving the same
View Patent ↗A liquid crystal display device includes a plurality of common electrodes arranged so as to counter pixel electrodes extending in the row direction on a substrate. First and second voltage supply lines to supply first and second voltages to the common electrodes are connected with the common electrodes through a first switch circuit. A second switch circuit is arranged between the first voltage supply line and signal lines to switch a connection between the first voltage supply line and the signal lines. A gate open circuit is connected to scan lines to simultaneously supply a signal to switch on the pixel electrodes to all the scan lines. In case the power supply of the liquid crystal display device is turned off, a control circuit starts the power OFF driving operation to set the potential of the pixel electrode and the common electrode to substantially same by switching the first and second switch circuits.
1. A liquid crystal display device, comprising:
a substrate;
a plurality of first electrodes arranged in a matrix of rows and columns on the substrate;
scan lines extending along with the first electrodes arranged in the row direction;
signal lines extending along with the first electrodes arranged in the column direction;
a pixel switch arranged in an intersection portion of the scan line and the column line to switch a connection between the signal line and the first electrode by a scan signal applied to the scan line;
a scan line driving circuit to sequentially scan the scan lines;
a plurality of second electrodes arranged so as to counter the first electrodes with an insulating layer positioned between the first electrodes and the second electrodes, and the second electrodes extend along with the pixels in the row direction;
a first voltage supply line to supply a first voltage to the second electrode;
a second voltage supply line to supply a second voltage to the second electrode;
a control circuit;
a first switch circuit arranged between the first and second voltage supply lines and the second electrodes to switch a connection between the first voltage supply line and the second electrodes, and a connection between the second voltage supply line and the second electrodes by a control signal outputted from the control circuit;
a second switch circuit arranged between the first voltage supply line and the signal line to switch a connection between the first voltage supply line and the signal line by the control signal outputted from the control circuit; and
a gate open circuit to receive signals from the scan line driving circuit and the control circuit, the gate open circuit supplying a signal to switch on the pixel witch to the scan line, wherein
the first switch circuit includes a first switching element to switch a connection between the first voltage supply line and the second electrode and a second switching element to switch the connection between the second voltage supply line and the second electrode under control by the control circuit;
the second switch circuit includes a third switching element to switch the connection between the first voltage supply line and the signal line under control by the control circuit,
the gate open circuit includes a NOT circuit to receive a signal outputted from the signal line driving circuit, and a NAND circuit to receive the output signal from the NOT circuit and the control signal from the control circuit; and
the control circuit switches on the first switching element, switches off the second switching element, and switches on the third switching element by setting the control signal to a low level when the liquid crystal display device is powered off.
2. The liquid crystal display device according to claim 1 , wherein in case the power supply to the liquid crystal display device is turned off, the voltage supplied to the first electrode is substantially same as that supplied to the second electrode.
3. The liquid crystal display device according to claim 1 , wherein the liquid crystal display device uses one of the IPS mode and FFS mode.
4. The liquid crystal display device according to claim 1 , wherein the control circuit supplies control signals to connect the first voltage supply line with the second electrode by controlling the first switch circuit, to connect the first voltage supply line with the signal line by controlling the second switch circuit, and to simultaneously supply the scan signals to switch on the pixel switches to all the signal lines through the gate open circuit when the liquid crystal display device is powered off.
5. The liquid crystal display device according to claim 1 , wherein the first electrode is a pixel electrode and the second electrode is a common electrode.
6. The liquid crystal display device according to claim 1 , wherein
in case the power supply of the liquid crystal display device is turned off, the control circuit starts the power OFF driving operation, and the power supply to the control circuit is turned off after a predetermined time passes.
7. A liquid crystal display device, comprising:
a first substrate;
a second substrate opposite the first substrate including;
a plurality of pixel electrodes arranged in a matrix of rows and columns,
scan lines extending along with the pixel electrodes arranged in the row direction,
signal lines extending along the pixel electrodes arranged in the column direction,
a pixel switch arranged in an intersection portion of the scan line and the column line to switch a connection between the signal line and the pixel electrode by a scan signal applied to the scan line,
a scan line driving circuit to sequentially scan the scan lines,
a source line driving circuit to supply picture signals to the signal lines,
a plurality of common electrodes arranged so as to counter the pixel electrodes with an insulating layer positioned between the common electrodes and the second electrodes, the common electrodes extending along with the pixels in the row direction,
a first voltage supply line to supply a first voltage to the common electrode,
a second voltage supply line to supply a second voltage to the common electrode,
a control circuit,
a first switch circuit arranged between the first and second voltage supply lines and the common electrodes to switch a connection between the first voltage supply line and the common electrodes, and a connection between the second voltage supply line and the common electrodes by a control signal outputted from the control circuit,
a second switch circuit arranged between the first voltage supply line and the signal line to switch a connection between the first voltage supply line and the signal line by the control signal outputted from the control circuit, and
a gate open circuit to receive signals from the scan line driving circuit and the control circuit, the gate open circuit supplying a signal to switch on the pixel electrode,
a liquid crystal layer held between the first and second substrates;
wherein in case the power supply of the liquid crystal display device is turned off, the control circuit starts the power OFF driving operation to set the potential of the pixel electrode and the voltage of the common electrodes substantially equal, and the power supply to the control circuit is turned off after a predetermined time passes,
the first switch circuit includes a first switching element to switch a connection between the first voltage supply line and the second electrode, and a second switching element to switch the connection between the second voltage supply line and the second electrode under control by the control circuit;
the second switch circuit includes a third switching element to switch the connection between the first voltage supply line and the signal line under control by the control circuit;
the gate open circuit includes a NOT circuit to receive a signal outputted from the signal line driving circuit, and a NAND circuit to receive the output signal from the NOT circuit and the control signal from the control circuit; and
the control circuit switches on the first switching element, switches off the second switching element, and switches on the third switching element by setting the control signal to a low level when the liquid crystal display device is powered off.
8. The liquid crystal display device according to claim 7 , wherein in case the power supply to the liquid crystal display device is turned off, a black display signal is written in all the pixel electrodes.
9. The liquid crystal display device according to claim 7 , the liquid crystal display device uses one of the IPS mode and FFS mode.
10. The liquid crystal display device according to claim 7 , wherein the polarity of the potential impressed to the liquid crystal layer is inversed for every one or more scan lines by changing the potential of the common electrodes.
11. A method of driving a liquid crystal display device including;
a substrate,
a plurality of first electrodes arranged in a matrix of rows and columns on the substrate,
scan lines extending along with the first electrodes arranged in the row direction,
signal lines extending along with the first electrodes arranged in the column direction,
a pixel switch arranged in an intersection portion of the scan line and the column line to switch a connection between the signal line and the first electrode by a scan signal supplied to the scan line,
a scan line driving circuit to sequentially scan the scan lines,
a plurality of second electrodes arranged so as to counter the first electrodes in the row direction with an insulating layer positioned between the first electrodes and the second electrodes,
a first voltage supply line to supply a first voltage to the second electrode,
a second voltage supply line to supply a second voltage to the second electrode,
a control circuit,
a first switch circuit arranged between the first and second voltage supply lines and the second electrodes to switch a connection between the first voltage supply line and the second electrodes, and a connection between the second voltage supply line and the second electrodes by a control signal outputted from the control circuit,
a second switch circuit arranged between the first voltage supply line and the signal line to switch a connection between the first voltage supply line and the signal line by the control signal outputted from the control circuit, and
a gate open circuit to receive signals from the scan line driving circuit and the control circuit and supply a signal to switch on the pixel switch, wherein
the first switch circuit includes a first switching element to switch a connection between the first voltage supply line and the second electrodes and a second switching element to switch the connection between the second voltage supply line and the second electrode under control by the control circuit;
the second switch circuit includes a third switching element to switch the connection between the first voltage supply line and the signal line under control by the control circuit,
the gate open circuit includes a NOT circuit to receive a signal outputted from the signal line driving circuit, and a NAND circuit to receive the output signal from the NOT circuit and the control signal from the control circuit; and
the control circuit switches on the first switching element, switches off the second switching element, and switches on the third switching element by setting the control signal to a low level when the liquid crystal display device is powered off,
the method comprising: when the power supply to the liquid crystal display device is turned off,
(a) connecting the first voltage supply line with the second electrode by controlling the first switch circuit;
(b) connecting the first voltage supply line with the signal line by controlling the second switch circuit; and
(c) supplying a signal to simultaneously switch on the pixel switches connected with all the signal lines to the gate open circuit.
12. The method of driving a liquid crystal display device according to claim 11 , wherein in case the power supply of the liquid crystal display device is turned off, the control circuit starts the power OFF driving operation, and the power supply to the control circuit is turned off after a predetermined time passes.
13. The method of driving a liquid crystal display device according to claim 12 , wherein in the case the power supply of the liquid crystal display device is turned off, a black display signal is written in all the pixel electrodes.
14. The method of driving a liquid crystal display device according to claim 11 , the liquid crystal display device uses one of the IPS mode and FFS mode.
15. The method of driving a liquid crystal display device according to claim 11 , wherein the first electrode is a pixel electrode and the second electrode is a common electrode.
16. The method of driving a liquid crystal display device according to claim 11 , wherein the polarity of the potential impressed to the liquid crystal layer is inversed for every one or more scan lines by changing the voltage of the second electrode.