1. Field of the Invention
The present invention relates to a liquid crystal display device.
2. Description of the Related Art
In a liquid crystal display device having pixels arranged in a matrix form, light is allowed to pass or blocked depending upon whether or not a voltage is applied to electrodes each corresponding to the pixels, and the display operation is conducted by controlling the transmission/nontransmission of light.
When a conductor for applying a voltage to electrodes is short-circuited or open-circuited, it is not possible to apply such a voltage to the respective electrode. The pixel corresponding to this conductor cannot be applied with a voltage, so that it is always at the display state of no-voltage application, with the result that the display control for the pixel cannot be conducted. Namely, the pixel becomes a defective-pixel.
In a display device wherein light is blocked when a voltage is applied to electrodes corresponding to pixels, it is impossible to block the light transmission through such a defective-pixel. When normal pixels surrounding such a defective-pixel are operated so as to block the light transmission, such a defective-pixel appears as a bright spot, thereby extremely degrading the display quality of the display device.
In a display device wherein thin film transistors (hereinafter, referred to as "TFTs") are used as switching elements, when an insulation failure occurs in a TFT, a voltage is always applied to the electrode connected to this defective TFT.
In a display device wherein TFTs are used and wherein light is not blocked when a voltage is applied to electrodes corresponding to pixels, it is impossible to block the light transmission through such defective-pixel. When normal pixels surrounding such a defective-pixel are operated so as to block the light transmission, such a defective-pixel appears as a bright spot, thereby extremely degrading the display quality of the display device.
In order to prevent such defective-pixel from being generated, conventionally, each pixel is connected to two conductors so that, even if one of the two conductors is damaged, the display operation of the corresponding pixel is not affected by this failure. Alternatively, each pixel is divided into two portions and provided with a plurality of electrodes so that, when a voltage cannot be applied to one of the plurality of electrodes, the display operation of the corresponding pixel is performed using the other electrodes.
In a liquid crystal display device wherein each pixel is connected to two conductors or divided into two portions and provided with a plurality of electrodes, there is a problem in that the circuit is complex in configuration and therefore it is difficult to design and construct the complicated circuit. Moreover, the complicated circuit and the increased number of conductors cause a problem in that an large area is required for forming the conductors, resulting in the reduced area of the electrodes and the lowered luminous intensity of the display.
When a plurality of electrodes are used for displaying one pixel, there is a problem in that the burden of the circuit for driving the electrodes is heavy.
Even if the countermeasures in the prior art are taken, when both the two conductors connected to a pixel are broken or when all of the conductors respectively connected to the electrodes constituting a pixel are broken, it is not possible to prevent a bright spot from being produced.