Display device, data driver, and display controller

The invention provides a display device, a data driver and a display controller. The data driver receives an image signal, generates a positive-polarity gradation data signal and a negative-polarity gradation data signal with respect to a predetermined reference voltage on the basis of the image signal, and outputs the positive-polarity gradation data signal to one of a first data line group and asecond data line group which divide a plurality of data lines into two. And outputting a gray scale data signal with negative polarity to the other one. The data driver generates, as a positive-polarity gradation data signal, a first signal indicating data pulses each having a positive-polarity voltage value corresponding to a luminance level of each pixel based on an image signal at a predetermined period, and generates, as a negative-polarity gradation data signal, a second signal indicating a negative-polarity gradation data value corresponding to a luminance level of each pixel based on the image signal. The seco