Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-05-12
2003-04-08
Nguyen, Chanh (Department: 2775)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S097000
Reexamination Certificate
active
06545656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device. The invention also relates to electrooptical apparatus using the liquid crystal display device.
2. Description of the Prior Art
Recently, the technique of fabricating thin film transistors (TFTs) on cheap glass substrates is being rapidly developed. The reason therefore lies in that the demand for active matrix liquid crystal display devices is increasing.
An active matrix liquid crystal display device is constituted in such a manner that a pixel portion is comprised of several hundred thousands to several millions of pixels which are matrix-wise disposed, a pixel TFT is disposed in each of the pixels, and the charges entering and leaving the pixel electrode connected to each pixel TFT are controlled by the switching function of the pixel TFT.
Recently, active matrix liquid crystal display devices are coming into wide use not only as the displays of the so far popularly used notebook type personal computers but also as the displays of desk top type personal computers.
Personal computers are required to display a plurality of pieces of information (including character information and image information) at a time; and thus, effects have been made to enhance the display ability of personal computers, that is, to enhance the image resolution and the realization of multi-gradation display (desirably, full-color display).
As a result of such enhancement in the display ability of personal computers, active matrix liquid crystal display device as the display device thereof is being improved. Thus, a digital driving type active matrix liquid crystal display device which is easy to effect interface with a personal computer and in which the high speed driving of the drivers can be achieved, and the display ability can thus be enhanced, is drawing attention.
To a digital driving type active matrix liquid crystal display device, digital video data are inputted from data sources such as personal computer. In the active matrix liquid crystal display device with digital drivers, it is necessary to provide a D/A conversion circuit (which is referred to as DAC: Digital-Analog Converter, in some cases). There are various kinds of D/A conversion circuits.
As one of the features of active matrix liquid crystal display device with digital driver, there can be pointed out the fact that the pixels corresponding to one line can be driven at the same time, in other words, line-sequential driving can be realized with relative ease.
Further, in the case of realizing the screen enlargement of the matrix liquid crystal display device and rendering the matrix liquid crystal display device highly precise and minute, the TN mode (twist nematic mode) using the known nematic liquid crystal cannot be said to be sufficient in its response speed.
Thus, recently, a report has been made of active matrix liquid crystal display device using an antiferroelectric mixed liquid crystal which has a V-shaped electrooptical characteristic, that is, which has a response speed faster by two or three figures than that of the nematic liquid crystal.
However, in the case this antiferroelectric mixed liquid crystal with a V-shaped electrooptical characteristic is used in an active matrix liquid crystal display device, the “image persistence” is more apt to take place than in the case of using nematic liquid crystal, thus leading to the problem of image deterioration.
SUMMARY OF THE INVENTION
Thus, the present invention has been achieved in view of the above-mentioned problems; the invention realizes a liquid crystal display device in which the deterioration of the image due to image persistence can be prevented.
According to the invention, a liquid crystal display device is provided, which comprises
a pixel portion in which a plurality of pixel TFTs are matrix-wise disposed,
a source driver and a gate driver which feed a plurality of the TFTs with picture signals, and
a ferroelectric liquid crystal material which has substantially no threshold value,
characterized in that
one frame is constituted by a plurality of sub-frames, and,
during at least one of a plurality of the sub-frames, the display by a reset signal is performed.
According to the invention, there is further provided a liquid crystal display device comprising
a pixel portion in which a plurality of pixel TFTs are matrix-wise disposed,
a source driver and a gate driver which feed a plurality of the TFTs with picture signals, and
a ferroelectric liquid crystal material which has substantially no threshold value,
characterized in that
one frame is constituted by a plurality of sub-frames, and
during at least one of a plurality of the sub-frames, the display of black by a reset signal is performed.
According to the invention, there is further provided a liquid crystal display device comprising
a pixel portion in which a plurality of pixel TFTs are matrix-wise disposed,
a source driver and a gate driver which feed a plurality of the TFTs with picture signals, and
a ferroelectric liquid crystal material which has substantially no threshold value,
characterized in that
one frame is constituted by n sub-frames (n stands for a natural number of 2 or greater), and
during m sub-frames of the n sub-frames (1≦m<n, m stands for a natural number), the display by a reset signal is performed.
According to the invention, there is further provided a liquid crystal display device comprising
a pixel portion in which a plurality of pixel TFTs are matrix-wise disposed,
a source driver and a gate driver which feed a plurality of the TFTs with picture signals, and
a ferroelectric liquid crystal material which has substantially no threshold value,
characterized in that
one frame is constituted by n sub-frames (n stands for a natural number of 2 or greater), and
during m sub-frames of the n sub-frames (1≦m<n, m stands for a natural number), the display of black by a reset signal is performed.
According to the invention, there is further provided a liquid crystal display device comprising
a pixel portion in which a plurality of pixel TFTs are matrix-wise disposed,
a source driver and a gate driver which feed a plurality of the TFTs with picture signals, and
a ferroelectric liquid crystal material which has substantially no threshold value,
characterized in that
the display in one frame is constituted by the displays in a plurality of sub-frames,
the displays in a plurality of the sub-frames are formed in such a manner that picture signals which are equal to each other in absolute value but opposite to each other in polarity are applied as a pair to the same pixel TFTs mentioned above, and
during at least one of a plurality of the sub-frames, the picture display of black by a reset signal is performed.
According to the invention, there is further provided a liquid crystal display device comprising
a pixel portion in which a plurality of pixel TFTs are matrix-wise disposed,
a source driver and a gate driver which feed a plurality of the TFTs with picture signals, and
a ferroelectric liquid crystal material which has substantially no threshold value,
characterized in that
the display in one frame is formed by the displays in m sub-frames (m stands for a natural number),
during at least n sub-frames of the m sub-frames, the picture displays of black by a reset signal is performed (n stands for a natural number, and m>n), an
the displays in (m-n) sub-frames are formed in such a manner that picture signals which are equal to each other in absolute value but opposite to each other in polarity are applied as a pair to the same pixel TFTs mentioned above.
Here, the liquid crystal display device according to the invention will now be described in more detail on the basis of embodiments thereof. However, the liquid crystal display device according to the invention is not limited to the following embodiments.
The liquid crystal display device according to the invention uses a ferroelectric liquid crystal material; particularly an antiferroelectric mixed liquid crystal that
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Nguyen Chanh
Semiconductor Energy Laboratory Co,. Ltd.
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