Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-01-03
2003-12-02
Nguyen, Chanh (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S103000
Reexamination Certificate
active
06657610
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid-crystal display device which is suitably used particularly in a method of selecting plural scanning electrodes in the form of lines at the same time and driving them, and to a method of driving the same.
BACKGROUND ART
Generally, since liquid-crystal display devices have features, such as small size and low profile, low power consumption, and flat-panel display, they are widely used in display portions of wristwatches, portable game machines, notebook-type personal computers, liquid-crystal televisions, car navigation devices, and other electronic devices.
As methods of driving a liquid-crystal display panel, there are a driving method of selecting scanning electrodes one at a time and driving them, and an MLS (multi-line selection) driving method (refer to International Application Publication No. WO93/18501) in which all scanning electrodes are grouped in advance and a scanning signal is simultaneously output to plural adjacent scanning electrodes belonging to the same group in a predetermined period. The MLS driving method has an advantage in that power consumption can be reduced.
An example of a conventional liquid-crystal display device using an MLS driving method will now be described with reference to
FIGS. 11
to
13
. As shown in
FIG. 11
, a conventional liquid-crystal display device
100
has a liquid-crystal display panel
101
. As shown in
FIG. 12
, the liquid-crystal display panel
101
has a substrate having plural scanning electrodes (common electrodes) Y (Y
1
, Y
2
, . . . Ym) in the form of lines, a substrate having plural signal electrodes (segment electrodes) X (X
1
, X
2
, . . . Xn) in the form of lines, and a liquid-crystal layer (not shown) interposed between the two substrates. In order to drive the liquid-crystal display panel
101
, a liquid-crystal driving circuit
102
supplies, to each scanning electrode Y, a scanning signal which can differ according to each scanning electrode and supplies, to each signal electrode X, a data signal which can differ according to each signal electrode. A liquid-crystal driving voltage generation circuit
103
, which is connected to an input end of the liquid-crystal driving circuit
102
, generates a liquid-crystal driving voltage. A driving control circuit
104
is connected to the input ends of the liquid-crystal driving circuit
102
and the liquid-crystal driving voltage generation circuit
103
. When the driving control circuit
104
receives display data and control data, the driving control circuit
104
generates a display signal and supplies it to the liquid-crystal driving circuit
102
and the liquid-crystal driving voltage generation circuit
103
.
The liquid-crystal driving circuit
102
comprises a driving circuit
105
on the scanning side which generates a scanning signal which is output to a scanning electrode Y of the liquid-crystal display panel
101
and a driving circuit
106
on the signal side which generates a data signal which is output to a signal electrode X thereof when the liquid-crystal driving voltage and the display signal are received.
Next, the driving operation of the liquid-crystal display device
100
is described with reference to
FIGS. 12 and 13
. In this technique, the scanning electrodes Y are grouped in advance so that plural (
3
in the example of the figures) adjacent scanning electrodes belong to the same group. The driving circuit
105
on the scanning side drives three scanning electrodes Y belonging to the same group at the same time. That is, the driving circuit
105
on the scanning side generates a scanning signal corresponding to each of the three scanning electrodes Y in a predetermined horizontal scanning period T. Then, another group is driven at the same time, and the process proceeds to the driving of another group in sequence. On the other hand, the driving circuit
106
on the signal side generates a data signal corresponding to each one of the signal electrodes X
1
, X
2
, . . . Xn.
Specifically, as shown in part (a) of
FIG. 13
, the three scanning electrodes Y
1
, Y
2
, and Y
3
of the first group are selected in the first horizontal scanning period T, scanning signals are applied to these scanning electrodes Y
1
, Y
2
, and Y
3
, and at the same time, data signals are applied to the signal electrodes X. As shown in
FIG. 13
, the scanning signal and the data signal can change in an interval of a selection period &Dgr;t even within the same horizontal scanning period T. In the next horizontal scanning period T, as shown in part (b) of
FIG. 13
, the scanning electrodes Y
4
, Y
5
, and Y
6
of the next group are selected, and scanning signals having a waveform similar to that supplied to the scanning electrodes Y
1
, Y
2
, and Y
3
are applied to those electrodes. The application of the data signals to the signal electrodes X is performed continuously from the previous horizontal scanning period T, and the waveform is different from the previous one. In this manner, the process proceeds to the driving of the next group, and when the driving of the final group is terminated, the process returns to the driving of the first group. The period of time required for the driving of all the scanning electrode groups to be completed once, that is, the period of time required to scan one display area of the liquid-crystal display panel
101
once, is called “one frame” (as indicated by F in FIG.
13
).
Since the voltage level of the scanning signal exists at two levels, +V
2
and −V
2
, if the number of scanning electrodes Y belonging to one group (the number of scanning electrodes which are selected at one time) is denoted as h, the number of pulse patterns which can be realized by one group in one selection period &Dgr;t is 2
h
. That is, for example, as shown in
FIG. 13
, in a case where three scanning electrodes Y are selected at the same time, the number of pulse patterns which can be realized by one group in one selection period &Dgr;t is 2
3
=8. In the first selection period &Dgr;t in the first horizontal scanning period T, the scanning electrode Y
1
is off (voltage=−V
2
), the scanning electrode Y
2
is off, and the scanning electrode Y
3
is off. In the next selection period &Dgr;t, the scanning electrode Y
1
is off, the scanning electrode Y
2
is off, and the scanning electrode Y
3
is on (voltage=+V
2
), and in sequence, a different pulse pattern is used in each selection period &Dgr;t.
The data signal applied to each signal electrode X is determined by the on/off of each of the pixels (3 pixels in the case of 3-line simultaneous driving) which are objects for display at the same time on that signal electrode, and the voltage level of the scanning signal applied to the scanning electrode Y. For example, in this conventional technique, during the period in which the voltage of a pulse of a scanning signal applied to the scanning electrodes Y
1
, Y
2
, and Y
3
which are selected at the same time is positive, the pixel display is assumed to be on; during the period in which the voltage of the pulse is negative, the pixel display is assumed to be off; and the on/off of the display data is compared with the voltage level of the scanning signal at each selection period &Dgr;t, so that the data signal is set according to the number of mismatches.
Specifically, in the waveforms of the scanning signals sent to the scanning electrodes Y
1
, Y
2
, and Y
3
in part (a) of
FIG. 13
, during the period in which a voltage of +V
2
is applied, the pixel display is assumed to be on; during the period in which a voltage of −V
2
is applied, the pixel display is assumed to be off; a pixel in
FIG. 12
whose display is indicated as a black circle mark is assumed to be on, and a pixel whose display is indicated as a white circle mark is assumed to be off. The displays of the pixels at which the signal electrode X
1
intersects the scanning electrodes Y
1
, Y
2
, and Y
3
in
FIG. 12
are on, on, and off, in that order. It is assumed that data signals for obta
Bell Paul A.
Gabrik Michael T.
Nguyen Chanh
Seiko Epson Corporation
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