Method for driving liquid crystal display device

A driving method of a display device which comprises:

• a display panel comprising a pixel circuit portion and a gate line driver circuit for driving the pixel circuit portion;
• and
• a touch panel superimposed on the display panel,
• the driving method comprising:
• displaying a moving image in a first period at a first refresh rate;
• stopping supply of a start pulse to the gate line driver circuit in a second period after the first period;
• stopping supply of a clock signal to the gate line driver circuit in the second period after stopping the supply of the start pulse;
• and
• displaying a still image in a third period after the second period at a second refresh rate which is smaller than the first refresh rate,
• wherein the pixel circuit portion comprises a pixel electrode and a first transistor electrically connected to the pixel electrode, the first transistor comprising a first oxide semiconductor layer including a channel formation region over a substrate, and
• wherein the gate line driver circuit comprises a second transistor, the second transistor comprising a second oxide semiconductor layer including a channel formation region over the substrate.

A display device comprising:

• a display panel comprising a pixel circuit portion and a gate line driver circuit for driving the pixel circuit portion;
• a touch panel superimposed on the display panel;
• a comparison circuit configured to compare image signals in each of pixels in order to determine if an image is a moving image or a still image;
• and
• a display control circuit configured to control operation of the gate line driver circuit in accordance with a determination by the comparison circuit,
• wherein, when the image is a moving image, the display control circuit is configured to control the gate line driver circuit so that the moving image is displayed at a first refresh rate,
• wherein, when the image is a still image, the display control circuit is configured to control the gate line driver circuit so that the still image is displayed at a second refresh rate smaller than the first refresh rate,
• wherein the pixel circuit portion comprises a pixel electrode and a first transistor electrically connected to the pixel electrode, the first transistor comprising a first oxide semiconductor layer including a channel formation region over a substrate,
• wherein the gate line driver circuit comprises a second transistor, the second transistor comprising a second oxide semiconductor layer including a channel formation region over the substrate, and
• wherein an off current per micrometer in a channel width of the first transistor is less than or equal to 1×10−17 A/μm.