Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-04-25
2004-04-20
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S094000, C345S087000, C345S099000, C345S096000, C345S098000, C345S102000, C345S095000, C345S208000
Reexamination Certificate
active
06724360
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antiferroelectric liquid crystal display, such as a liquid crystal display panel or a liquid crystal optical shutter array, that has a liquid crystal layer of antiferroelectric liquid crystal.
2. Description of the Related Art
Liquid crystal panels using antiferroelectric liquid crystals have been researched vigorously since it was reported in Japanese Unexamined Patent Publication No. 2-173724 by Nippondenso and Showa Shell Sekiyu that such liquid crystal panels provide wide viewing angles, are capable of fast response, and have good multiplexing characteristics.
In traditional liquid crystal displays using conventional liquid crystals such as nematic liquid crystals, when a rapidly changing image is displayed on the screen, the screen cannot respond quickly to the changes of the image. For example, in a video game, when an image of a ball moving around is displayed on a liquid crystal display, there occurs the phenomenon that the contour of the ball cannot be displayed distinctly and the image is blurred (this phenomenon will hereinafter be referred to as the “image trailing phenomenon”). Previously, this image trailing phenomenon has been believed to occur because of the slow switching speeds of liquid crystal molecules. However, a recent research report shows that not only the slow switching speeds of liquid crystal molecules but the traditionally employed liquid crystal driving method is also responsible for the image trailing phenomenon. That is, the report says that in a scanning period during which an image based on display data is written to the pixels, if the image is written to the pixels without once resetting the previous image display, the previous image persists in the eye of the person viewing the display, thus causing the image trailing phenomenon.
It has been believed that antiferroelectric liquid crystals are resistant to the image trailing phenomenon because of their fast switching speeds compared with other conventional liquid crystals. However, recent research has revealed that antiferroelectric liquid crystal displays are resistant to the image trailing phenomenon, not only because of their fast switching speeds but also because of their unique driving method, that is, the inclusion of a reset period which, as earlier described, is supposed to contribute to reducing the image trailing phenomenon.
In the previous research, however, it has not been made clear as to how the antiferroelectric liquid crystals can be controlled most effectively to reduce the image trailing phenomenon. The prior known method has had the further problem that by simply providing the reset period, the image trailing phenomenon cannot be completely eliminated when displaying a moving image based on rapidly changing display data.
SUMMARY OF THE INVENTION
In view of the above situation, it is an object of the present invention to provide, in an antiferroelectric liquid crystal display using an antiferroelectric liquid crystal, an antiferroelectric liquid crystal display having an effective reset period, and achieving a good display quality by setting an optimum reset period when displaying an image, whether it be a moving image or a still image.
To attain the above object, the antiferroelectric liquid crystal display according to the present invention is equipped with an antiferroelectric liquid crystal panel having an antiferroelectric liquid crystal sandwiched between a pair of substrates, wherein the antiferroelectric liquid crystal display is provided with at least one scanning period when carrying out a display based on one set of display data, and the scanning period comprises a selection period for determining the state of the antiferroelectric liquid crystal, a non-selection period for holding the state determined in the selection period, and a reset period for resetting pixels to a black display state before initiating the selection period, and wherein the antiferroelectric liquid crystal display includes a device for adjusting the length of the reset period according to the speed of change in the display data.
The length of the reset period is increased when the speed of change in the display data is fast, and is reduced when the speed is slow.
The antiferroelectric liquid crystal display further includes a backlight and a device for adjusting the brightness of the backlight according to the length of the reset period.
The brightness of the backlight is increased when the length of the reset period is increased, and is reduced when the length is reduced.
The speed of change in the display data is detected by comparing display data of approximately successive screens (frames).
The antiferroelectric liquid crystal display is characterized in that the antiferroelectric liquid crystal display includes a pair of polarizers whose polarization axes are oriented substantially at right angles to each other, in that the antiferroelectric liquid crystal is capable of exhibiting an antiferroelectric state, a first ferroelectric state, and a second ferroelectric state, in that the pair of polarizers are arranged so that the polarization axis of either one of the polarizers substantially coincides with the average molecular long axis direction of the antiferroelectric liquid crystal in the absence of an applied voltage, and in that in the reset period, the antiferroelectric liquid crystal is set to the antiferroelectric state.
The antiferroelectric liquid crystal display is also characterized in that the antiferroelectric liquid crystal display includes a pair of polarizers whose polarization axes are oriented substantially at right angles to each other, in that the antiferroelectric liquid crystal is capable of exhibiting an antiferroelectric state, a first ferroelectric state, and a second ferroelectric state, in that the pair of polarizers are arranged so that the direction of line bisecting the angle which is made by the polarization axes of the polarizers substantially coincides with the average molecular long axis direction of the antiferroelectric liquid crystal in the absence of an applied voltage, and in that, in the reset period, the antiferroelectric liquid crystal is set to the first or second ferroelectric state.
The antiferroelectric liquid crystal display according to another aspect of the invention is equipped with a backlight and an antiferroelectric liquid crystal panel having an antiferroelectric liquid crystal sandwiched between a pair of substrates, wherein the antiferroelectric liquid crystal display is provided with at least one scanning period when carrying out a display based on display data for one frame, and the scanning period includes a selection period for determining the state of the antiferroelectric liquid crystal, a non-selection period for holding the state determined in the selection period, and a reset period for resetting all pixels simultaneously to a white display state before initiating the selection period, and wherein the backlight is turned off during the reset period.
The antiferroelectric liquid crystal display includes a device for adjusting the length of the reset period according to the speed of change in the display data.
The length of the reset period is increased when the speed of change in the display data is fast, and is reduced when the speed is slow.
The speed of change in the display data is detected by comparing display data of approximately successive screens (frames).
The antiferroelectric liquid crystal display further includes a device for adjusting the brightness of the backlight according to the length of the reset period.
The brightness of the backlight is increased when the length of the reset period is increased, and is reduced when the length is reduced.
The antiferroelectric liquid crystal display is characterized in that the antiferroelectric liquid crystal display includes a pair of polarizers whose polarization axes are oriented substantially at right angles to each other, in that the antiferroelectric liquid crystal is capable
Citizen Watch Co. Ltd.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Shankar Vijay
Shapiro Leonid
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