Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-04-19
2004-04-13
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S099000
Reexamination Certificate
active
06720947
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for driving an anti-ferroelectric liquid crystal display (LCD) panel, and more particularly, to a method for driving an anti-ferroelectric LCD panel in which a plurality of parallel signal electrode lines are arranged over anti-ferroelectric liquid crystal cells (LCs), and a plurality of parallel scan electrode lines are arranged below the anti-ferroelectric LCs, perpendicular to the signal electrode lines.
2. Description of the Related Art
Referring to
FIG. 1
, a general anti-ferroelectric LCD
1
includes an anti-ferroelectric LCD panel
11
and a driving apparatus thereof. The anti-ferroelectric LCD panel
11
has a series of parallel signal electrode lines SL
1
, SL
2
, SL
3
, . . . , SLn arranged over anti-ferroelectric LCs, and a series of parallel scan electrode lines CL
1
, CL
2
, CL
3
, . . . , CLm arranged below the anti-ferroelectric LCs, wherein the signal electrode lines SL
1
, SL
2
, SL
3
, . . . , SLn are perpendicular to the scan signal electrode lines CL
1
, CL
2
, CL
3
, . . . , CLm. The signal electrode lines SL
1
, SL
2
, SL
3
, . . . , SLn and the scan electrode lines CL
1
, CL
2
, CL
3
, . . . , CLm are formed of a transparent conductive material, for example, indium tin oxide (ITO).
As shown in
FIG. 1
, the driving apparatus includes a segment driver
12
, a modulation signal generator
131
and a common driver
132
. The driving apparatus receives a data signal DATA, a shift clock signal SCK, a frame signal FLM and a latch clock signal LCK from a host, for example, from a notebook computer. The segment driver
12
stores the received data signal for each of the signal electrode lines SL
1
, SL
2
, SL
3
, . . . , SLn, according to the shift clock signal SCK. The segment driver
12
applies a signal voltage corresponding to the stored data signal DATA to each of the signal electrode lines SL
1
, SL
2
, SL
3
, . . . , SLn according to the latch clock signal LCK.
The frame signal FLM indicates the starting point of a frame. The modulation signal generator
131
divides the frequency of the latch clock signal LCK to generate a modulation signal. The polarity of the output voltages from the segment driver
12
and the common driver
132
are controlled by the modulation signal.
The common driver
132
applies a corresponding scan voltage to each of the scan electrode lines CL
1
, CL
2
, CL
3
, . . . , CLm in succession according to the controls of the latch clock signal LCK, the frame signal FLM and the modulation signal. As a result, the orientation state of the anti-ferroelectric LCs of a pixel to be displayed is shifted, thereby transmitting light or blocking the transmission of light.
FIG. 2
illustrates the waveform of a common drive voltage applied to a scan electrode line by a conventional driving method.
Referring to
FIG. 2
, during a first selection period t
s1
corresponding to a unit slot (SL), a scanning selection voltage +V
s
is applied, and the orientation state of anti-ferroelectric LCs selected depending on a corresponding display data signal S
s
are shifted into a ferro-electric state, which allows transmission of light from the outside. During the subsequent first holding period t
H1
, a holding voltage +V
H
, which has the same polarity as the scanning selection voltage +V
s
, but its level is lower than that of the scanning selection voltage +V
s
, is applied, and the selected LCs are maintained in the ferroelectric state. During the subsequent first reset period t
R1
, ground voltage is applied and the LCs are restored to the anti-ferroelectric state from the ferroelectric state. The first reset period t
R1
is required for smooth inverse driving during the subsequent unit driving period.
During the subsequent second selection period t
S2
, a scanning selection voltage −V
S
is applied and anti-ferroelectric LCs selected depending on a corresponding display data signal S
s
are shifted into the ferroelectric state, which allows transmission of light from the outside. During the subsequent second holding period t
H2
, a holding voltage −V
H
, which has the same polarity as the scanning selection voltage −V
s
, but its level is higher than that of the scanning selection voltage −V
s
, is applied and the selected LCs are maintained in the ferroelectric state. During the subsequent second reset period t
R2
, ground voltage is applied and the LCs are restored to the anti-ferroelectric state from the ferroelectric state. The second reset period t
R2
is required for smooth inverse driving of the subsequent unit driving period.
FIG. 3
shows the change of transmittancy of the selected LCs during the first or second reset period t
R1
or t
R2
of FIG.
2
. In
FIG. 3
, reference numeral
31
indicates a circular waveform in the state where a probe voltage is not applied, and reference numerals
311
,
312
,
313
and
314
indicate interference waveforms when the probe voltage is applied. As described with reference to
FIG. 2
, during the first or second reset period t
R1
or t
R2
, the level of voltage applied to a scanning electrode line is changed from the holding voltage +V
H
or −V
H
to ground voltage, so that the selected LCs in the ferroelectric state are restored to the anti-ferroelectric state. As a result, light transmittancy of the selected LCs is lowered, as shown in FIG.
3
.
In anti-ferroelectric LCD panels, brightness increases with a rising state restoration time in the selected LCs. However, when an anti-ferroelectric LCD panel is simply driven by the conventional method as illustrated in
FIG. 2
, it takes a long period of time to restore the orientation state of LCs in the first or second reset period t
R1
or t
R2
, and thus brightness of the anti-ferroelectric LCD panel decreases.
FIG. 4
illustrates the waveform of a common drive voltage applied to a scan electrode line by another conventional driving method. In
FIG. 4
, like reference numerals are used to refer to like operations of FIG.
2
. Compared with
FIG. 2
, the driving waveform of
FIG. 4
further includes single activation periods t
B1
, and t
B2
, for which a single blanking pulse is applied, between the first holding period t
H1
and the first reset period t
R1
, and between the second holding period t
H2
and the second reset period t
R2
.
FIG. 5
illustrates the change of transmittancy of the selected LCs during the first and second reset periods t
R1
and t
R2
. In
FIG. 5
, reference numeral
51
indicates a non-active waveform that appears when applying the driving method of FIG.
2
. Reference numeral
521
indicates an active waveform that appears when applying the driving method of
FIG. 4
, and reference numerals
522
and
523
indicate interference waveforms when the probe voltage is applied. As shown in
FIG. 5
, the state restoration time becomes short due to the presence of the single activation periods t
B1 and t
B2
during each of which the signal blanking pulse is applied.
However, when the driving method of
FIG. 4
is applied, the state restoration is sensitive to temperature variations. In other words, when the neighboring temperature is higher or lower than room temperature, the single blanking pulse applied during each of the single activation periods t
B1
, and t
B2
acts as a noise component, so that the state restoration time cannot be reduced.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a method for driving an anti-ferroelectric liquid crystal display (LCD) panel, which can consistently reduce the time required for restoring the state in liquid crystal cells, regardless of ambient temperature changes.
To achieve the objective of the present invention, there is provided a method for driving an anti-ferroelectric liquid crystal display (LCD) panel in which a plurality of parallel signal electrode lines are arranged over anti-ferroelectric liquid crystal cells (LCs) and a plurality of parallel scan electrode lines are
Yakovenko Sergei
Yoo Jeong-geun
Anyaso Uchendu O.
McGuireWoods LLP
Samsung SDI & Co., Ltd.
Saras Steven
LandOfFree
Method for driving an anti-ferroelectric liquid crystal... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for driving an anti-ferroelectric liquid crystal..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for driving an anti-ferroelectric liquid crystal... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3260302