Method for driving liquid crystal display device

A method for driving a liquid crystal display device that is capable of displaying a still image and a moving image, the liquid crystal display device comprising a transistor electrically connected to a pixel electrode, and a capacitor having a first electrode electrically connected to the pixel electrode and a second electrode electrically connected to a capacitor line, wherein a gate of the transistor is electrically connected to a gate line, the method comprising the steps of:

• supplying an image signal to the pixel electrode through the transistor by turning on the transistor in a writing period;
• and
• holding a potential of the pixel electrode by turning off the transistor in a holding period to display the still image,
• wherein a potential of the capacitor line is changed throughout the holding period,
• wherein a refresh rate during display of the still image is lower than a refresh rate during display of the moving image,
• wherein one frame period comprises the writing period and the holding period,
• wherein a channel formation region of the transistor comprises an oxide semiconductor,
• wherein the liquid crystal display device further comprises a current source circuit being electrically connected to the second electrode of the capacitor through the capacitor line, and
• wherein current flows in the current source circuit when the liquid crystal display device displays the still image.

A method for driving a liquid crystal display device, the liquid crystal display device comprising a transistor electrically connected to a pixel electrode, and a capacitor having a first electrode electrically connected to the pixel electrode and a second electrode electrically connected to a capacitor line,,

• the method comprising the steps of:
• supplying an image signal to the pixel electrode through the transistor by turning on the transistor in a writing period;
• and
• holding a potential of the pixel electrode by turning off the transistor in a holding period,
• wherein a potential of the capacitor line is lowered or raised monotonically at least during the holding period,
• wherein one frame period comprises the writing period and the holding period,
• wherein a channel formation region of the transistor comprises an oxide semiconductor,
• wherein the liquid crystal display device further comprises a current source circuit being electrically connected to the second electrode of the capacitor through the capacitor line, and
• wherein current flows in the current source circuit when the liquid crystal display device displays a still image.