1. A display device comprising: a display panel having a plurality of unit pixels, each unit pixel of the plurality of unit pixels comprising first and second sub-pixels alternately arranged in a same first vertical line and a third sub-pixel arranged in a second vertical line different than the first vertical line where the first and second sub-pixels are arranged; and an image processing unit for converting data such that first sub-pixels adjacent upward and downward to the second sub-pixel in each unit pixel are driven in cooperation with each other, and third sub-pixels adjacent left and right of the second sub-pixel in each unit pixel are driven in cooperation with each other, when an image is realized on a background image of the display panel while having a different brightness than the background image, the third sub-pixels are driven in cooperation with each other at leftmost and rightmost portions of the image having the different brightness than the background image to realize a color of the third sub-pixel.