Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-09-08
2003-05-27
Wu, Xiao (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S088000
Reexamination Certificate
active
06570554
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display using a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal.
Along with the recent developments of the so-called office automation (
0
A),
0
A apparatuses, typically exemplified by word-processors and personal computers, have been widely used. As such
0
A apparatuses have become prevalent in offices, there have been ever-increasing demands for portable-type
0
A apparatuses that can be used in offices as well as outdoors, and there have been also demands for small-size and light-weight of such apparatuses. Here, liquid crystal displays have come to be widely used as one of the means to achieve such an objective. Liquid crystal displays not only achieve small-size and light-weight, but also include an indispensable technique in an attempt to achieve low power consumption in portable
0
A apparatuses that are driven by batteries.
The liquid crystal displays are mainly classified into the reflection-type and the transmission-type. In, the reflection-type liquid crystal displays, light rays that have been made incident on the front face of a liquid crystal panel are reflected by the back face of the liquid crystal panel so that an image is visualized by the reflected light. In the transmission-type liquid crystal displays, transmitted light from a light source (backlight) placed behind the back face of a liquid crystal panel is used to visualize an image. Although those of the reflection-type are inferior in visibility due to irregularity in the amount of reflected light that depends on environment conditions, they are inexpensive and widely used as display devices with mono-color (for example, black/white display, etc.) for such as calculators and watches. However, they are not suitable for display devices for personal computers, etc. which carry out a multi-color or full-color display. For this reason, in general, transmission-type liquid crystal displays are used as display devices for personal computers, etc. which carry out a multi-color or full-color display.
Here, currently-used color liquid crystal displays are generally classified into the STN (Super Twisted Nematic) type and the TFT-TN (Thin Film Transistor-Twisted Nematic) type based upon the liquid crystal type to be used. Although those of the STN type have comparatively low manufacturing costs, they are susceptible to cross-talk, and comparatively slow in response speeds; therefore, they are not suitable for display for animation pictures. In contrast, those of the TFT-TN type have higher display quality as compared with the STN type; however, since, at present, their liquid crystal panel has a light transmittance as low as 4%, a back-light with high luminance is required. For this reason, those of the TFT-TN type have greater power consumption due to the back-light, resulting in a problem in use of carrying battery power-source. Moreover, the TFT-TN type have other problems with the response speed, particularly slow in response speed for displaying half tones, narrow viewing angle, difficulty in adjusting the color balance, etc.
Moreover, in the conventional liquid crystal displays, a back-light of white light is used and the white light is selectively transmitted through color filters of three primary colors so as to perform a multi-color or full-color display; that is, those of the color-filter type have been generally used. However, in the color-filter type, a display pixel is constituted by a certain area including adjacent three color filters as one unit; therefore, the resolution is lowered to virtually one-third. Moreover, the application of the color filters reduces the transmittance of the liquid crystal panel, resulting in a reduction in the luminance as compared with the case without color filters.
In order to solve the above-mentioned problems, a liquid crystal display (Japanese Patent Application Laid-Open No. 7-281150, etc.) has been proposed in which a ferroelectric liquid crystal element or an anti-ferroelectric liquid crystal element, which has a high response speed to an applied electric field, is used as its liquid crystal element, and the same pixel is allowed to emit light rays with the three primary colors sequentially color by color so as to provide a color display.
FIGS. 1 and 2
are graphs respectively show the electro-optical characteristics of the ferroelectric liquid crystal and anti-ferroelectric liquid crystal. As shown in
FIG. 1
, the light transmittance of the ferroelectric liquid crystal varies depending on the polarity of an applied voltage. In the case of the plus application, the light-transmittance increases in response to the applied voltage, and in the case of the minus application, the light-transmittance becomes zero independent of the magnitude of the applied voltage. Moreover, as shown in
FIG. 2
, the light-transmittance of the anti-ferroelectric liquid crystal increases in response to the applied voltage in both of the cases of the plus and minus applications, and in the case of zero of the voltage application, the light-transmittance becomes zero. Therefore, in the case when these ferroelectric liquid crystal and anti-ferroelectric liquid crystal are applied to a liquid crystal display, a voltage corresponding to pixel data is supplied to each pixel of a liquid crystal panel and the light-transmittance is adjusted so that a display is available.
In a liquid crystal display using a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal having the above-mentioned electro-optical characteristics, a liquid crystal panel, which uses a ferroelectric liquid crystal element or an anti-ferroelectric liquid crystal element that is capable of a high-speed response in hundreds to several &mgr; seconds order, and a back-light capable of emitting red, green and blue light rays in a time-divided manner are combined, and by synchronizing the switching of the liquid crystal element and the light emission of the back-light a color display is realized. In the case when the ferroelectric liquid crystal element or the anti-ferroelectric liquid crystal element is used as the liquid crystal material, the liquid crystal molecules are constantly maintained in parallel with the substrate (glass substrate) so that it is possible to provide a very wide viewing angle; therefore, no problem arises in practical use. Moreover, in the case when a back-light constituted by red, green and blue light-emitting diodes (LEDs) is used, it is possible to adjust the color balance by controlling currents flowing through the respective LEDs.
FIG. 3
is a block diagram that shows one example of the structure of a conventional liquid crystal display. To an image memory
52
included in a display control means
51
is supplied display data DD to be displayed on a liquid crystal panel
53
from, for example, an externally personal computer, etc. The image memory
52
temporarily stores the display data DD, and then transfers data of each pixel unit (hereinafter, referred to as pixel data PD) to a data driver
55
, and the data driver
55
outputs the pixel data PD thus transferred. Moreover, the display control means
51
outputs a control signal to a scan driver
56
, and the scan driver
56
controls the on/off operations of scan lines installed within the liquid crystal display panel
53
. Furthermore, the display control means
51
supplies a driving voltage to a back-light
54
so as to allow an LED array included in the back-light
54
to emit light.
FIG. 4
is a time chart that shows one example of a conventional display control carried out in such a liquid crystal display.
FIG. 4A
shows timing of light emissions of the LEDs of respective red, green and blue colors of the back-light
54
,
FIG. 4B
shows scanning timing of respective lines of the liquid crystal panel
53
, and
FIG. 4C
shows color-emitting states of the liquid crystal panel
53
.
As illustrated in
FIG. 4A
, the LEDs in the back-light
54
are allowed to emit light success
Kiyota Yoshinori
Makino Tetsuya
Shiroto Hironori
Yoshihara Toshiaki
Fujitsu Limited
Greer Burns & Crain Ltd.
Wu Xiao
LandOfFree
Liquid crystal display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3005729