In recent years, see-through displays have been attracting attention as the display devices for information display systems or digital signage. In a see-through display, the background (i.e., the rear-face side of the display panel) is visible in a see-through manner, whereby information to be indicated on the display panel is displayed as if overlaid on the background. As a result, a novel manner of display that was never possible with conventional display devices can be achieved. Thus, a see-through display has good appeal and eyecatchingness. Application of see-through displays to showcases and show windows has also been proposed.
In the case where a liquid crystal display device is used for a see-through display, its low efficiency of light utilization will be a detriment. The reasons for the low efficiency of light utilization of a liquid crystal display device are the color filters and polarizing plates, which are provided in generic liquid crystal display devices. The color filters and polarizing plates absorb light in specific wavelength regions or light of specific polarization directions.
This has led to the idea of using a liquid crystal display device of the field sequential method. Under the field sequential method, multicolor displaying is performed through time-division switching between colors of light with which a liquid crystal display panel is irradiated from an illumination element. This eliminates the need for color filters, thus improving the efficiency of light utilization. However, in the field sequential method, the liquid crystal display device needs to have a rapid response.
Patent Documents 1 and 2 disclose liquid crystal display devices having improved response characteristics because of an electrode structure being provided which is capable of switchably generating a vertical field and a lateral field across the liquid crystal layer. In the liquid crystal display devices disclosed in Patent Documents 1 and 2, a vertical field is generated across the liquid crystal layer in either one of the transition (rise) from a black displaying state to a white displaying state and the transition (fall) from a white displaying state to a black displaying state, while a lateral field (fringing field) is generated across the liquid crystal layer in the other. Therefore, the torque due to voltage application acts on the liquid crystal molecules in both of a rise and a fall, whereby good response characteristics are attained.
Patent Document 3 also proposes a liquid crystal display device which realizes a rapid response by allowing the alignment regulating force of an electric field to act on the liquid crystal molecules in both a rise and a fall.