1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for driving the liquid crystal display device.
2. Description of the Related Art
A technique for forming a thin film transistor (TFT) with the use of a semiconductor thin film formed over a substrate having an insulating surface has attracted attention. Thin film transistors are applied to a wide range of electronic devices such as integrated circuits (ICs) and image display devices (display devices).
An example of a display device including thin film transistors is an active matrix liquid crystal display device in which a thin film transistor is provided as a switching element in each pixel. Liquid crystal display devices are used in various fields ranging from portable devices such as mobile phones and notebook computers to large devices such as televisions. The reduction in power consumption is recognized as a major challenge for such electronic devices including a liquid crystal display device. For example, lower power consumption of a portable device leads to longer continuous operation time, and lower power consumption of a large television or the like saves money in electricity.
In a liquid crystal display device, video signals are always rewritten even while still images are displayed, and the rewriting operation consumes power. As a method for reducing such power consumption, for example, there has been reported a technique in which in still image display, an idle period that is longer than a scan period is provided as a non-scan period each time after a screen is scanned once to write video signals (e.g., see Patent Document 1 and Non-Patent Document 1).