Patent ID: 8866725

Claim:
A liquid crystal display device comprising: a display panel, the display panel comprising: a plurality of pixels each including a transparent electrode, a reflective electrode, a transistor electrically connected to the transparent electrode and the reflective electrode; and a first driver circuit configured to drive the plurality of pixels; an image processing circuit, the image processing circuit comprising: a memory circuit capable of storing image signals in successive frame periods; a comparison circuit configured to compare the image signals in the successive frame periods and calculate a difference; and a display control circuit; and a backlight portion, the backlight portion comprising: a plurality of light emitting elements; and a second driver circuit configured to drive the plurality of light emitting elements, wherein the transistor has a channel formation region comprising an oxide semiconductor, wherein the transparent electrode is partly in contact with and overlapped with the reflective electrode, wherein the transparent electrode and the reflective electrode are each configured to control an orientation state of liquid crystal, wherein the display panel is configured to be driven in a moving-image display mode or a still-image display mode, wherein in the moving-image display mode, the comparison circuit judges successive frame periods during which the difference is detected as a moving-image display period, the image processing circuit outputs a first signal to the display panel, the first driver circuit drives the display panel, the image processing circuit outputs a second signal to the backlight portion, and the second driver circuit drives the backlight portion, wherein, in the still-image display mode, the comparison circuit judges successive frame periods during which the difference is not detected as a still-image display period and the image processing circuit stops the output of the second signal to the backlight portion, wherein the image processing circuit is configured to control a supply of a clock signal to the first driver circuit, wherein the image processing circuit is configured to supply the clock signal to the first driver circuit in the moving-image display mode, wherein a still-image holding period, in which the clock signal is not supplied to the first driver circuit so that operation of the first driver circuit is stopped, is provided in the still-image display mode, and wherein a still-image is displayed on the display panel during the still-image holding period.