Display device, display driving method, and electronic apparatus

1. A display device comprising:

a pixel array portion including plural pixels in which display gradations of the plural pixels are controlled in accordance with written pixel signals, the plural pixels are disposed in a row direction and in a column direction;

plural scanning lines disposed in said pixel array portion and supplying scanning pulses to the pixels in the rows;

plural signal lines disposed in said pixel array portion and supplying the pixel signals to the pixels in the columns;

a scanning line driver successively supplying the scanning pulses to said plural scanning lines and causing the pixels in the rows to carry out write of the pixel signals outputted to the signal lines; and

a signal line driver outputting the pixel signals for the pixels to said plural signal lines, wherein

the signal line driver outputs, at least once in a frame period, a charge voltage with lower electric potential than a predetermined pixel signal voltage to each of said plural signal lines, the charge voltage being output in less than all horizontal periods of the frame period;

an electric potential of a channel portion of a pixel transistor is controlled in accordance with the scanning pulse in the pixel;

said signal line driver outputs the charge voltage to said signal lines at a frequency such that the electric potential of the channel portion of the pixel transistor is less than an electric potential of the pixel signal written to a pixel capacitor due to a leakage current; and a time interval Tcg at which said signal line driver outputs the charge voltage is expressed by:

Tcg≦Cch ×( VgL−Vcg )/( Ipx+Ips )

where Cch is a capacitance of said channel portion of said pixel transistor, VgL is the predetermined pixel signal voltage, Vcg is the charge voltage, Ipx is a pixel transistor leakage current caused to flow from the pixel capacitor to said channel portion, and Ips is a pixel transistor leakage current caused to flow from the signal line to said channel portion.

2. The display device according to claim 1 , wherein the charge voltage is set as a voltage falling within a range of being equal to or lower than a negative-polarity electric potential of a drive maximum gradation of the pixel signal, and being equal to or higher than a gate electric potential in an OFF phase of a pixel transistor which is controlled in accordance with the scanning pulse in the pixel.

3. The display device according to claim 1 , wherein said signal line driver outputs the charge voltage to said signal lines at a timing after a negative-polarity pixel signal is outputted.

4. The display device according to claim 1 , further comprising

a touch panel portion disposed so as to be superposed on a display area based on said pixel array; and

a detection scanning portion that performs detection scanning and obtains a touch signal to detect a touch on said touch panel portion, wherein

the scanning line driver performs write scanning to write pixel signal,

the detection scanning portion performs detection scanning to detect touch,

the write scanning and the detection scanning are performed plural times for one frame period in a time division manner; and

the charge voltage is output by said signal line driver for a period between the detection scanning and the write scanning.

5. A display driving method for use in a display device including a pixel array portion containing plural pixels in which display gradations of the plural pixels are controlled in accordance with written pixel signals and which are disposed in a row direction and in a column direction, plural scanning lines disposed in said pixel array portion and supplying scanning pulses to the pixels in the rows, plural signal lines disposed in said pixel array portion and supplying the pixel signals to the pixels in the columns, a scanning line driver, and a signal line driver, said display driving method comprising:

successively supplying the scanning pulses to said plural scanning lines and causing the pixels in the rows to carry out write of the pixel signals outputted to the signal lines by said scanning line driver;

outputting the pixel signals for the pixels to said plural signal lines,

outputting, at least once per frame period, a charge voltage with lower electric potential than a predetermined pixel signal voltage to each of said plural signal lines by said signal line driver, the charge voltage being output in less than all horizontal periods of the frame period; and

an electric potential of a channel portion of a pixel transistor being controlled in accordance with the scanning pulse in the pixel,

outputting the charge voltage by said signal line driver to said signal lines at a frequency in such a manner that the electric potential of the channel portion of the pixel transistor is less than an electric potential of the pixel signal written to a pixel capacitor due to a leakage current, wherein

a time interval Tcg at which said signal line driver outputs the charge voltage is expressed by:

Tcg≦Cch ×( VgL−Vcg )/( Ipx+Ips )

where Cch is a capacitance of said channel portion of said pixel transistor, VgL is the predetermined pixel signal voltage, Vcg is the charge voltage, Ipx is a pixel transistor leakage current caused to flow from the pixel capacitor to said channel portion, and Ips is a pixel transistor leakage current caused to flow from the signal line to said channel portion.

6. An electronic apparatus including a display device, said display device comprises:

a pixel array portion including plural pixels in which display gradations of the plural pixels are controlled in accordance with written pixel signals, the plural pixels are disposed in a row direction and in a column direction;

plural scanning lines disposed in said pixel array portion and supplying scanning pulses to the pixels in the rows;

plural signal lines disposed in said pixel array portion and supplying the pixel signals to the pixels in the columns;

a scanning line driver successively supplying the scanning pulses to said plural scanning lines and causing the pixels in the rows to carry out write of the pixel signals outputted to the signal lines; and

a signal line driver outputting the pixel signals for the pixels to said plural signal lines, wherein

the signal line driver outputs, at least once in a frame period, a charge voltage with lower electric potential than a predetermined pixel signal voltage to each of said plural signal lines, the charge voltage being output in less than all horizontal periods of the frame period;

an electric potential of a channel portion of a pixel transistor is controlled in accordance with the scanning pulse in the pixel;

said signal line driver outputs the charge voltage to said signal lines at a frequency such that the electric potential of the channel portion of the pixel transistor is less than an electric potential of the pixel signal written to a pixel capacitor due to a leakage current; and a time interval Tcg at which said signal line driver outputs the charge voltage is expressed by:

Tcg≦Cch ×( VgL−Vcg )/( Ipx+Ips )

where Cch is a capacitance of said channel portion of said pixel transistor, VgL is the predetermined pixel signal voltage, Vcg is the charge voltage, Ipx is a pixel transistor leakage current caused to flow from the pixel capacitor to said channel portion, and Ips is a pixel transistor leakage current caused to flow from the signal line to said channel portion.

7. The electronic apparatus according to claim 6 , wherein the charge voltage is set as a voltage falling within a range of being equal to or lower than a negative-polarity electric potential of a drive maximum gradation of the pixel signal, and being equal to or higher than a gate electric potential in an OFF phase of a pixel transistor which is controlled in accordance with the scanning pulse in the pixel.

8. The electronic apparatus according to claim 6 , wherein said signal line driver outputs the charge voltage to said signal lines at a timing after a negative-polarity pixel signal is outputted.