Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-09-12
2002-07-23
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S094000, C345S096000, C345S097000, C345S087000
Reexamination Certificate
active
06424329
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a system and a method for driving a nematic liquid crystal.
When two transparent flat plates having transparent electrodes and sandwiching a nematic liquid crystal are placed between two polarizing plates transmittance of light passing through the polarizing plates changes with voltages applied to the transparent electrodes.
Since liquid crystal display devices based on the above principle can be shaped flat and are operative with low electric power, they have been widely used in wrist watches, electronic calculating machines, and so forth. In recent years, they are also used in combination with color filters to form color display devices in note-type personal computers and small liquid crystal TV sets, for example. In such liquid crystal displays, dots of three colors, red, green and blue, are selectively combined to display desired colors. However, color filters are very expensive and need a high accuracy when bonded to panels. Moreover, they need a triple number of dots to ensure an equivalent resolution as compared with black-and-white liquid crystal display panels. Therefore, liquid crystal color panels require a triple number of drive circuits typically in the horizontal direction. This means an increase of the cost of drive circuits themselves and the cost for increased man hours for connecting drive circuits to the panel at a triple number of points.
That is, the use of color filters with liquid crystal panels to display color images involves many disadvantageous factors from the viewpoint of expense.
To avoid the problems caused by the use of color filters, color liquid crystal display devices as disclosed in Japanese Patent Laid-Open 1-179914(1989) have been proposed to display color images by combining a black and white panel and three-color back-lighting in lieu of color filters. Certainly, this method seems more likely to realize high-fidelity color images economically. Actually, however, because of the difficulty in driving liquid crystals at a high speed with conventional drive techniques, no such device has been brought into practice.
Another problem with conventional liquid crystal display devices was slow responses of liquid crystals. Due to this, liquid crystal display devices have been inferior to CRT displays especially when used as TV displays for displaying moving images or as personal computer displays required to follow quick movements of a mouse cursor.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a new system and a method for driving a nematic liquid crystal that can increase the speed of response of any conventional nematic liquid crystals, either TN-type or STN-type, to a value high enough to ensure a performance equivalent to or higher than the performance of a CRT display system when displaying color images by the three color back lighting method or reproducing moving images.
According to the present invention, there is provided a system for driving a nematic liquid crystal in a liquid crystal display device in which the nematic liquid crystal is confined between a common electrode and a segment electrode that are placed between two polarizing plates, comprising:
means for applying a sequence of selection pulses to the common electrode;
means responsive to the selection pulses to apply to the segment electrode a voltage corresponding to image data to be displayed; and
means for applying a voltage different from the voltage corresponding to the image data to the segment electrode in intervals where the selection pulses are not applied.
According to another aspect of the invention, there is provided a method for driving a nematic liquid crystal in a liquid crystal display device in which the nematic liquid crystal is confined between a common electrode and a segment electrode that are placed between two polarizing plates, comprising the steps of:
applying a sequence of selection pulses to the common electrode;
in response to the selection pulses, applying to the segment electrode a voltage corresponding to image data to be displayed; and
applying a voltage different from the voltage corresponding to the image data to the segment electrode in intervals where the selection pulses are not applied.
In both aspects of the invention, the voltage independent from the image data may be switched in level in response to intervals of the selection pulses.
The voltages to the common electrode and the segment electrode are preferably determined such that the voltage to the segment electrode be inverted in polarity when the selection pulse is applied to the common electrode.
The system preferably includes heater means for heating the nematic liquid crystal to a predetermined temperature.
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Chow Dennis-Doon
Flynn ,Thiel, Boutell & Tanis, P.C.
Nelson Alecia D.
Okita Masaya
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