Display device and method for driving the same

Abstract

It is an object to provide a display device in which a problem of light leakage from a liquid crystal element in black display is reduced or overcome and the contrast is improved. It is another object to provide a pixel circuit having a function to control a lighting state of a backlight based on each pixel. These objects are achieved by turning off a light-emitting element in display of a black gray scale, and by providing a light-emitting element in each pixel and providing, in a pixel circuit, a function to individually control lighting and non-lighting of the light-emitting element depending on a gray scale to perform display. When a backlight is provided in each pixel, a light-emitting element that is a backlight is turned off when a black gray scale is displayed, whereby reduction in contrast due to light leakage from a liquid crystal element can be prevented.

What is claimed is: 
     
         1 . A display device comprising:
 a pixel portion including a light-emitting element and a liquid crystal element which is overlapped with the light-emitting element;   a data line electrically connected to the liquid crystal element; and   a comparator electrically connected to the data line and the light-emitting element.