Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-08-13
2001-08-07
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S096000, C345S097000, C345S209000, C345S210000
Reexamination Certificate
active
06271819
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for driving an electro-optical display device such as ferroelectric liquid crystal, dence etc.
Recently, the ferroelectric liquid crystal is drawing attentions of researchers as a successor of the TN type liquid crystal and a display device utilizing such a ferroelectric liquid crystal is currently researched.
The display mode of ferroelectric liquid crystal is categorized into the complex refraction type display mode and guest host type display mode. In the case of driving a display device of such modes, the driving method which has been employed for the conventional TN type liquid crystal cannot be used because the display condition (brightness of display) is controlled by changing the direction of applied electric field, unlike the conventional TN type liquid crystal. Namely, when a voltage, although it may be low level, is continuously applied even in one direction, the ferroelectric liquid crystal may at last respond to such voltage. Therefore, a special driving method is necessary for such display mode.
The driving methods which have been developed so far sometimes allow, during time-shared non-selected period, repeated application of small amplitude pulses having the polarity opposite to that of a pulse for display, and trigger drop of contrast in case that a number of digits to be displayed increases.
Moreover, a voltage to be applied is not a perfect AC voltage and a voltage of the one polarity is applied longer than a voltage of the polarity. Accordingly, there arises a problem that if a device is driven for a long period of time, the transparent electrode for display may be blackened or double color pigment may be discolored or liquid crystal may by deteriorated.
It Since the conventional driving methods are followed by such problems, these methods cannot be considered as the definitive method and therefore advent of the optimum driving method has long been expected.
Moreover, it has been supposed to be difficult to gene rate the intermediate tone in display for the ferroelectric liquid crystal and a driving method for generating the gradation has not yet been developed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for driving an electro-optical display device which prevents even after a long period of driving that the transparent electrode is blackened, double color pigment is discolored and liquid crystal is deteriorated.
It is another object of the present invention to provide a method for driving an electro-optical display device which does not bring about drop of contrast even in case a number of digits increases.
It is further object of the present invention to provide a method for driving an electro-optical display device which can generate an intermediate tone of display.
It is still further object of the present invention to provide a method for driving an electro-optical display device which shortens the period of time-sharing driving and remarkably increases a number of digits for display.
REFERENCES:
patent: 4655561 (1987-04-01), Kanbe et al.
patent: 4715688 (1987-12-01), Harada et al.
patent: 5092665 (1992-03-01), Kanbe et al.
Adams & Wilks
Lao Lun-Yi
Seiko Precision Inc.
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