Scanning line driving circuit of a liquid crystal display

Details Scanning line driving circuit of a liquid crystal display Scanning line driving circuit of a liquid crystal display

1998-06-24

2001-09-18

Brier, Jeffery (Department: 2672)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

C345S092000, C345S204000

Reexamination Certificate

active

06292163

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to liquid crystal displays (LCDs) where a charge transfer scanning circuit is integrated into a LCD panel, and more particularly to a scanning line driving circuit for LCDs having discharging path for automatically discharging charges on scanning lines.
In general, a gate driver IC for scanning a LCD panel and a source driver IC for providing data to the LCD panel are respectively fabricated and then the driver ICs are packaged to the LCD panel. Because the conventional LCD packaging techniques fabricate driver ICs separately and package the driver ICs to the LCD panel, they have disadvantages in that the yield is reduced and the production cost rises.
To solve the problems occurred in case where driver ICs are separately fabricated and are packaged to a LCD panel, LCDs is which driver ICs are integrated into the LCD panel are proposed.
FIG. 1
shows a LCD disclosed in Korean Patent Application No. 96-77694, in which a gate driver IC is integrated into a LCD panel. The gate driver-integrated LCD comprises a LCD panel
100
, a gate driver IC
200
integrated into the LCD panel
100
, a data driver IC
300
and a controller
500
.
The LCD panel
100
comprises an upper glass substrate
110
where a color filter array is formed, a lower glass substrate
120
where a thin film transistor (TFT) array is formed, and LCs, not shown in
FIG. 1
, injected between the upper and lower glass substrates
110
and
120
. Together with the TFT array, the gate driver IC
200
which drives scanning lines SL
11
through SL
1
n
of the LCD panel
100
is integrated in the lower glass substrate
120
.
In the same manner as conventional LCDs, the data driver IC
300
is mounted on a tape carrier package(TCP)
400
and a pad part
310
of the data driver IC
300
is wire-bonded to the LCD panel
100
. The controller
500
is for providing clock signals and data signals to the gate driver IC
200
integrated into the LCD panel
100
and the data driver IC
300
. The controller
500
provides two-phase clock signals to the gate driver IC
300
through the LCD panel
100
and the data driver IC
300
.
The gate driver IC
200
that is, the scanning line driving circuit is integrated into the portion of the lower glass substrate
120
which is not overlapped with the upper glass substrate
110
in an integrating TFT array. The detailed diagram of the scanning line driving circuit is shown in FIG.
2
. The charge transfer type scanning line driving circuit
200
comprises a plurality of driving means
211
-
21
n
for driving scanning lines SL
11
-SL
1
n
of the LCD panel
100
, respectively.
The driving means
211
-
21
n
generate scanning line driving signals Vg_out
1
-Vg_outn to drive the scanning lines SL
11
-SL
1
n
, respectively. Each of the driving means
211
-
21
n
comprises a first TFT T
111
-T
11
n
for charge transfer, in which a clock signal Q
1
or Q
2
from the controller
500
is applied to a gate thereof, a capacitor C
111
-C
11
n
for charge, which is connected to a source and the gate of the first TFT T
111
-T
11
n
, and a second TFT T
121
-T
12
n
for a buffer in which the source of the first TFT T
111
-T
11
n
is connected to a gate thereof and which is driven by the first TFT T
111
-T
11
n
to generate the scanning line driving signal Vg_out
1
-Vg_outn to the scanning line SL
11
-SL
1
n
of the LCD panel
100
.
In the plurality of driving means
211
-
21
n
, a predetermined voltage Vin of high level is applied to a drain of the first TFT T
111
of the first driving means
211
. A source of the first TFT of one of the plurality of driving means is connected to a drain of the first TFT of the following driving means. For example, the source of the first TFT T
112
of the second driving means
212
is connected to the drain of the first TFT T
113
of the third driving means
213
. A gate voltage Vgh of the predetermined high level is applied to drains of the second TFTs T
121
-T
12
n.
The operation of the charge transfer type scanning line driving circuit will be described in detail below. Supposed that the first clock signal Q
1
of two-phase clock signals Q
1
and Q
2
is turned on and the second clock signal Q
2
is turned off. The first clock signal Q
1
is applied to the first driving means
211
. The first transistor T
111
is tuned on by the first clock signal Q
1
and the input voltage Vin of a predetermined high level is provided to the gate of the second transistor T
121
through the first TFT T
111
. The second transistor T
121
is turned on by the input voltage Vin. The gate voltage Vgh is provided to the first scanning line SL
11
of the LCD panel
100
as the first scanning line driving signal Vg_out
1
through the second TFT T
121
.
Subsequently, the first clock signal Q
1
is turned off and the second clock signal Q
2
is turned on. The second clock signal Q
2
is provided to the second driving means
212
and charges charged to the capacitor C
111
are applied to the drain of the first TFT T
112
of the second driving means
212
. The first TFT T
112
of the second driving means
212
is turned on by the second clock signal and the charges charged in the capacitor C
111
are provided to the gate of the second TFT T
122
through the first transistor T
112
and to the capacitor C
112
. The second transistor T
122
is turned on. Accordingly, the gate voltage Vgh is provided through the second transistor T
122
as the second scanning line driving signal Vg_out
2
to the second scanning line SL
12
of the LCD panel
100
.
As above described, the first through the nth driving means
211
-
21
n
are driven to generate the first through the nth scanning line driving signals Vg_out
1
-Vg_outn in turn with repeated turning-on and turning-off of two clock signals Q
1
and Q
2
. Therefore, the first through the nth scanning lines SL
11
-SL
1
n
of the LCD panel
100
are driven in turn by the first through the nth scanning line driving signals Vg_out
1
-Vg_outn.
As compared with the conventional LCDs in which the driver ICs are fabricated and then packaged to the LCD panel, the LCD of FIG.
1
and
FIG. 2
can improve yield and cost down by integrating the gate driver IC into the lower glass substrate together with the TFT array. However, because the scanning driving circuit of
FIG. 2
has no discharge path, the charges charged to the scanning line can not be discharged, when the following scanning line driving signal is generated, following the generation of any one of the scanning line driving signals. For example, when the second scanning line driving signal Vg_out
2
is generated to the second scanning line SL
12
, following the generation of the first scanning line driving signal Vg_out
1
to the first scanning line SL
11
, charges charged to the first scanning line driving signal SL
11
are not discharged. Accordingly, the second TFT T
122
of the second driving means
212
is turned on and the second scanning line driving signal Vg_out
2
is applied to the second scanning line SL
12
while the first scanning line driving signal Vg_out
1
is present in the first scanning line SL
11
, thereby resulting in deteriorating picture quality of LCD.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a scanning line driving circuit-integrated LCD capable of solving the problem according to package of driver IC and minimizing size thereof.
Another object of the present invention is to provide a scanning line driving circuit-integrated LCD having discharging means which prevents the deterioration of picture quality.
According to the present invention, there is provided a scanning line driving circuit of a liquid crystal display(LCD) including a LCD panel where liquid crystals are injected between an upper substrate and a lower substrate in which a thin film transistor array is integrated thereto and the scanning line driving circuit for driving scanning lines of the LCD panel, comprising: a driving means for generating scanning line driving signals for driving the scanning lines of the LCD panel according to e

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