1. Field of the Invention
The present invention relates to a liquid crystal display device, and in particular, to a transmissive liquid crystal display device.
2. Description of the Related Art
Liquid crystal display devices are generally known as image display devices. The liquid crystal display device is used in display sections of notebook personal computers, monitors, car navigation systems, alpha calculators, medium- and small-sized television receivers, and the like. The liquid crystal display device comprises an array substrate, an opposite substrate, and a liquid crystal layer. Among the liquid crystal display devices, a transmissive type and a semi-transmissive type comprising a backlight unit have a high contrast characteristic. Thus, the liquid crystal display device is used for a high-display-capacity apparatus with a plurality of image portions and is specifically used in display sections of notebook personal computers, monitors, car navigation systems, television receivers, and the like.
To offer a high contrast characteristic, almost all the liquid crystal display devices use a polarizing plate and a switching element such as TFT (Thin Film Transistor) or TFD (Thin Film Diode), and have a color filter for color display. However, this configuration may reduce the utilization efficiency and transmittance of light. This may in turn increase the power consumption of the backlight unit and prevent a sufficient display luminance from being achieved.
On the other hand, currently adopted display modes include a twisted nematic (TN) mode and a vertical alignment (VA) mode (hereinafter referred to as a VA mode). These modes allow liquid crystal molecules to be uniformly arranged when no electric field is applied to a liquid crystal layer, and allow the arrangement of the liquid crystal molecules to be uniformly changed when an electric field is applied to the liquid crystal layer.
In recent years, the electric field applied to the liquid crystal layer is controlled to arrange the liquid crystal molecules in each pixel in a plurality of (at least two) directions. The liquid crystal display device performs pixel orientation division, for example, as shown in Jpn. Pat. Appln. KOKAI Publication No. 2004-355032. This makes it possible to average the dependence of a visual angle on the direction in which the liquid crystal molecules are arranged, enabling the improvement of a visual angle characteristic, which has been an objective of the TN and VA modes.
The pixel orientation division results in an area in the pixel in which the liquid crystal molecules are arranged in a different direction. Thus, a phase difference in backlight is reflected even in white display pixels, and part of the backlight is absorbed by the polarizing plate. In particular, in a multi-domain VA (Vertical Alignment) mode (hereinafter referred to as an MVA mode), Schlieren orientation occurs inevitably, that is, a cross-shaped area is inevitably created in which the liquid crystal molecules are not uniformly arranged. Thus, as described above, the phase difference in the backlight is reflected even in the white display pixels, and part of the backlight is absorbed by the polarizing plate. As described above, the liquid crystal display device with the pixel orientation division offers a lower light utilization efficiency than the liquid crystal display device without the pixel orientation division.
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USPTO Backgrounds