Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-08-04
2002-04-02
Wu, Xiao (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S096000, C345S100000
Reexamination Certificate
active
06366271
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for driving an LCD device comprising a large size, high resolution color LCD panel and to a driving circuit for the LCD.
In general, an LCD crystal display device comprises an LCD panel, a scanning signal circuit for supplying a scanning signal to the LCD panel, and a liquid crystal drive circuit for supplying an image signal to the LCD panel.
The above LCD panel comprises a scanning signal line and an image signal line which is perpendicular to the scanning signal line and connected to the liquid crystal drive circuit. The scanning signal lines are disposed in parallel with one another, and connected to the scanning signal circuit.
Furthermore, the LCD panel comprises pixels arranged in matrix pattern such that the scanning signal line and the image signal line serve as boundary lines. On each crossing part of the scanning signal line and image signal line, there is provided a TFT (thin film transistor) as an active element.
The LCD device can display a prescribed image signal by (1) giving a plurality of image signals outputted from the liquid crystal drive circuit to each image signal line, (2) selecting the specified scanning signal line by the scanning signal outputted from the scanning signal circuit, (3) turning ON only the TFT connected to the selected scanning signal line, (4) applying the respective predetermined image signal only to the pixel including TFT in ON state, (5) controlling transmittance of light of liquid crystal of each pixel by the potential difference of the applied predetermined image signal.
In general, in the large size LCD device having high resolution color LCD panel, in order to maintain the operating frequency of the image data which is a signal inputted to the liquid crystal drive circuit to a level lower than the highest frequency (maximum operating frequency) in the range in which the liquid crystal drive circuit can be operated, there may be a case of providing the liquid crystal drive circuits for example on and under the LCD panel.
In the conventional LCD device as described above, when the number of pixels is increased to improve resolution, the time for the TFT to charge the image signal is restricted to be short. Also, when the size of screen is enlarged (that is, large screen is used), length of line such as the image signal line, scanning signal line requires to be long, and the wiring load becomes large. Accordingly, there arises such problems that the wave forms of the image signal and scanning signal are distorted, or the transmission speed of the image signal on the image signal line or transmission speed of the scanning signal on the scanning signal line becomes slow. Accordingly, due to the mutual effects of the preceding and succeeding scanning signal or image signal, the image signal at the time of application to the pixel results in difference from the prescribed amount.
As mentioned above, when the number of pixels is increased and at the same time the size of screen is enlarged, there arises crosstalk which shows variation in the brightness of the pixels surrounding the pattern and defective display such as flicker in which the brightness of the pixels around the pattern varies at times, and the quality of display is remarkably lowered.
With respect to the driving method for the LCD device in consideration of the prevention of degradation of display quality, there is an alternating current driving method. The alternating current driving method is a method of driving the LCD device while inverting (changing) the polarity of the image signal in a predetermined cycle period. In the present specification, the polarity of the signal means the polarity of the voltage of the signal.
In case of adopting the alternating current drive method, in general, the polarity of the output from the odd number from the image drive (hereinafter referred to simply as “odd number output”) is different from the polarity of the output from the even number from the image drive (hereinafter referred to as “even number output”). In order to change the polarity of the odd number output from the polarity of the even number output, a drive circuit for outputting the polarity inversion signal capable of optionally inverting the polarity (hereinafter to be referred to as “polarity inverting drive circuit”) is provided, for example, in the timing control circuit.
FIG. 12
is an illustrative view showing an example of conventional liquid crystal drive circuit. In
FIG. 12
, the part
1
shows a liquid crystal drive circuit, and
101
to
106
show the output terminals of the liquid crystal drive circuit
1
. In
FIG. 12
, there are shown only six output terminals of the liquid crystal drive circuit
1
. The first output terminal, third output terminal and (2 m+1)-th output terminal denoted by numerals
101
,
103
and
105
are the odd number output terminals to output the odd number outputs. Furthermore, the second output terminal, fourth output terminal and (2 m+2)-th output terminal denoted by numerals
102
,
104
and
106
are the odd number output terminals to output the odd number outputs, wherein m is 0 (Zero) or natural number.
FIG. 13
is an illustrative view showing the polarity inversion signal, and examples of the polarities of the odd number output and even number output outputted from the liquid crystal drive circuit shown in FIG.
12
. In
FIG. 13
, there are shown from the top the polarities of polarity inversion signal, odd number output, and even number output. In
FIG. 13
, the horizontal direction shows time, and the vertical direction shows voltage with respect to the polarity inversion signal only.
In
FIG. 13
, when the polarity inversion signal is in high level, the polarity of the odd number output is positive, and when the polarity inversion signal is in low level, the polarity of the odd number output is negative, and the polarity of the even number output is negative.
FIGS.
14
(
a
) and
14
(
b
) and FIGS.
15
(
a
) and
15
(
b
) are the illustrative views showing an example of the concept of the line relating to the pixels of the conventional LCD panel. FIG.
14
(
a
) is an illustrative view showing an LCD device in n frame (n is 0 (Zero) or natural number), and FIG.
14
(b) is an illustrative view showing an LCD device in n+1 frame. FIG.
15
(
a
) is an illustrative view showing an LCD device in n+2 frame, and FIG.
15
(
b
) is an illustrative view showing an LCD device in n+3 frame.
In FIGS.
14
(
a
) and
14
(
b
) and FIGS.
15
(
a
) and
15
(
b
), the part
1
a
shows an upper liquid crystal drive circuit provided on the upper side of the LCD panel, numeral
1
b
shows a lower liquid crystal drive circuit provided on the under side of the LCD panel, numeral
2
shows a scanning signal circuit, and numeral
4
shows a timing control circuit for controlling the timing for varying the voltage of the signal outputted from the upper liquid crystal drive circuit
1
a
, lower liquid crystal drive circuit
1
b
, and scanning signal circuit
2
to the predetermined amounts. Furthermore, numeral
11
a
shows an image signal line connected to the output terminal of the upper liquid crystal drive circuit
1
a
,
11
b
shows an image signal line connected to the output terminal of the lower liquid crystal drive circuit
1
b
, and numeral
12
shows a scanning signal line connected to the output terminal of the scanning signal circuit
2
. The symbol “+” or “−” shown in the white circle schematically shows the polarity, i.e., positive or negative, of the image signal to be applied to the pixel. Furthermore, the upper image signal line
11
a
and image signal line
11
b
labeling “R” are the signal lines dealing with the pixels for red color, the upper image signal line
11
a
and lower image signal line
11
b
labeling “G” are the signal lines dealing with the pixels for green color, and the upper image signal line
11
a
and lower image signal line
11
b
labeling “B” are the signal lines dealing with the pixels for blue color, re
Kohno Yasuhiko
Nishimura Masaru
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wu Xiao
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