Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1996-12-13
2001-05-08
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S089000, C345S096000, C345S100000, C345S209000
Reexamination Certificate
active
06229515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device having selection switching elements arranged in units of pixels or scanning lines, and a driving method for the device.
2. Description of the Related Art
Liquid crystal display devices are low-profile, lightweight devices which can be driven on low voltages, and hence are widely used for wristwatches, desk calculators, wordprocessors, personal computers, compact video games, and the like. With the recent, increased demand for pen input electronic notebooks, a demand has arisen for portable terminal devices (PDA).
As a method of driving a liquid crystal display device, a driving method of reversing the polarities within the same frame is available. This driving method includes a signal line reversal method of reversing the polarity in units of signal lines, a horizontal polarity reversal (to be referred to as H reversal hereinafter) method of reversing the polarity in units of scanning lines, and a dot reversal method of reversing the polarity between adjacent pixels. These driving methods can compensate for flicker components (e.g., plane flickers) resulting from polarity reversal. The H inversion driving method has been widely used especially as the demands have arisen for arrangement of signal line drivers on one side with a decrease in cabinet size, and for low-withstand voltage drivers for a decrease in power consumption.
In a large-screen, high-resolution LCD, as the number of signal lines increases, the capacitive component between the common electrode and each signal line becomes large. In addition, the resistive component greatly changes in accordance with the distance from the feeding point because of the sheet resistance of the common electrode. For this reason, when the polarity of the common electrode is reversed, since the time constant of the common electrode varies within the frame as shown in
FIG. 1
, the voltage value of the common electrode varies (the waveform becomes blunt). Since this phenomenon depends on the signal voltage, when window display is performed, picture degradation known as crosstalk occurs. In order to solve this problem, the sheet resistance of the common electrode may be decreased. However, this method has its own limitations, and cannot provide a satisfactory effect.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide a liquid crystal display device and a driving method therefor, which can prevent picture degradation such as crosstalk.
According to the present invention, there is provided a liquid crystal display device comprising:
a pair of substrates, on at least one of which pixels or scanning lines and switching elements for selecting the pixels or the scanning lines are arranged, a liquid crystal material sandwiched between the substrates, driving means for driving a pixel group arrayed on each of selected scanning lines with the same polarity, and polarity reversal means for compensating for flickers by reversing the polarity, wherein in a display area, a scanning line selection order is arbitrarily determined, and polarities are reversed on the basis of the determination result so as not to produce a bundle of scanning lines having the same polarity within one field.
In addition, according to the present invention, there is provided a driving method for a liquid crystal display device including a pair of substrates, on at least one of which A pixels or scanning lines and switching elements for selecting the pixels or the scanning lines are arranged, and a liquid crystal material sandwiched between the substrates, wherein a display area is divided into n sub-fields for sequentially displaying one frame image along a time axis, each of the sub-fields is basically constituted by A÷n×m (where A is a positive integer, n is a positive integer ranging from 3 to A, and m is a positive integer equal to or smaller than n) pixels or scanning lines, and the pixels or the scanning lines are selected at predetermined intervals in each of the sub-fields, comprising driving a pixel group arrayed on each of selected scanning lines with the same polarity, compensating for flickers by reversing the polarity, and selecting the pixels or the scanning lines in each of the sub-fields at predetermined intervals.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
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Itoh Goh
Okumura Haruhiko
Hjerpe Richard
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
Tran Henry N.
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