Liquid crystal display device viewable in dim ambient light

摘要

An object is to provide a liquid crystal display device in which image display can be recognized even in an environment where light is dim around the liquid crystal display device. Another object is to provide a liquid crystal display device capable of image display in both modes of a reflective mode in which external light is used as a light source and a transmissive mode in which a backlight is used. One pixel is provided with a pixel electrode having both of a region where light incident through a liquid crystal layer is reflected and a region having a light-transmitting property, so that image display can be performed in both modes of a reflective mode in which external light is used as a light source and a transmissive mode in which a backlight is used.

主权项

1. 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; anda 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; anda display control circuit; and a backlight portion, the backlight portion comprising:
a plurality of light emitting elements; anda 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.