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, thereby conducting displaying such that information which is displayed by the display panel is overlaid on the background. 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, since displaying in the respective colors is sequentially performed, displaying one multicolor image requires multiple times of displaying with different color rays (e.g., three times for red light displaying, green light displaying, and blue light displaying). In other words, as compared to a display device which utilizes color filters, operation at a higher driving frequency is required in order to achieve a similar frame rate of displaying. For this reason, in a liquid crystal display device driven by the field sequential method, the liquid crystal display panel is often required to have a rapid response.
Patent Document 1 discloses a liquid crystal display device having improved response characteristics because of an electrode structure being provided which is capable of switchably generating a vertical field or a lateral field across the liquid crystal layer. In the liquid crystal display device disclosed in Patent Document 1, 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.
However, when the liquid crystal display device disclosed in Patent Document 1 is used for a see-through display, the problem of background blur (it being perceived as double images) may occur and a deteriorated display quality may result, as has been confirmed by the inventors. For suitability in a see-through display, as is described in Patent Document 2 by the Applicants, for example, it is preferable to achieve a transparent displaying state (see-through displaying) in the absence of any voltage applied across the liquid crystal layer, in a liquid crystal display device which is adapted to be able to generate a vertical field and a lateral field across the liquid crystal layer.