Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-12-24
2004-08-24
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169300, C345S082000, C345S084000, C345S092000
Reexamination Certificate
active
06781320
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. 2001-87390 filed in Korea on Dec. 28, 2001, which is hereby incorporated by reference for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix organic electroluminescence display device including an organic emissive layer.
2. Discussion of the Related Art
A cathode ray tube is widely used as a display device such as a television and a monitor, and the cathode ray tube has a large size, heavy weight, and high driving voltage. Therefore, flat panel displays, which have properties of being thin, low weight and low power consumption, have been proposed. The flat panel displays include a liquid crystal display device, a plasma display panel, a field emission display device, and an electroluminescence display device.
Electroluminescence display devices may be categorized into inorganic electroluminescence display devices and organic electroluminescence display devices according to source material for exciting carriers. The organic electroluminescence display device has attracted considerable attention lately due to its high brightness, low driving voltage, and natural color images from all colors of a visible light spectrum. Additionally, the organic electroluminescence display device has great contrast ratio because of self-luminescence. The organic electroluminescence display device can easily display moving images due to short response time of several microseconds, and is not limited by a viewing angle. The organic electroluminescence display device is stable at a low temperature, and its driving circuit can be fabricated easily because it is driven by low voltage. Besides, manufacturing process of the organic electroluminescence display device is relatively simple.
In general, an organic electroluminescence display device emits light by injecting an electron from a cathode electrode and a hole from an anode electrode into an emissive layer, combining the electron with the hole, which generates an exciton, and transiting the exciton from an excited state to a ground state.
Because of its luminous mechanism similar to a light emitting diode, the organic electroluminescence display device may be called an organic light emitting diode (OLED).
Organic electroluminescence display devices are classified into a passive matrix type and an active matrix type according to a driving method.
The passive matrix organic electroluminescence display device has a simple structure and is manufactured through a simple process. However, the passive matrix organic electroluminescence display device has high power consumption and is difficult to manufacture to have a large area. Additionally, aperture ratio in the passive matrix organic electroluminescence display device decreases according to the increasing number of electro lines.
Therefore, the passive matrix organic electroluminescence display device is widely used as a small size display device. On the other hand, the active matrix organic electroluminescence display (AMOELD) device is widely used as a large size display device.
An active matrix organic electroluminescence display (AMOELD) device according to the related art will be described hereinafter more in detail.
FIG. 1
is an equivalent circuit diagram for a pixel of an AMOELD device in the related art. In
FIG. 1
, a pixel of an AMOELD device includes a switching thin film transistor (TFT)
4
, a driving thin film transistor (TFT)
5
, a storage capacitor
6
, and an electroluminescent diode
7
.
A gate electrode of the switching TFT
4
is electrically connected to a gate line
1
, and a source electrode of the switching TFT
4
is electrically connected to a data line
2
. A drain electrode of the switching TFT
4
is electrically connected to a gate electrode of the driving TFT
5
. A drain electrode of the driving TFT
5
is electrically connected to an anode electrode of the electroluminescent diode
7
, and a source, electrode of the driving TFT
5
is electrically connected to a power line
3
. A cathode electrode of the electroluminescent diode
7
is grounded. The storage capacitor
6
is electrically connected to the gate electrode and the source electrode of the driving TFT
5
.
When a signal is applied to the gate electrode of the switching TFT
4
through the gate line
1
, the switching TFT
4
turns on. At this time, a signal from the data line
2
is transmitted to the gate electrode of the driving TFT
5
through the switching TFT
4
and is stored in the storage capacitor
6
. Then, the driving TFT
5
is turned on by the signal from the data line
2
, and a signal from the power line
3
is transmitted to the electroluminescent diode
7
through the driving TFT
5
. Therefore, light is emitted from the electroluminescent diode
7
. Brightness of the device of
FIG. 1
is regulated by controlling current passing through the electroluminescent diode
7
.
Here, even though the switching TFT
4
turns off, the driving TFT
5
maintains in an “on state” because of the signal stored in the storage capacitor
6
. Accordingly, light is emitted by current continuously passing through the electroluminescent diode
7
until the next signal is transmitted to the gate electrode of the driving TFT
5
through the switching TFT
4
.
FIG. 2
illustrates a plan view for the pixel of an AMOELD device in the related art. In
FIG. 2
, a gate line
41
and a data line
61
cross each other and define a pixel region “P”. A power line
67
is formed parallel to the data line
61
.
A switching TFT “T
S
” is formed at the crossing of the gate line
41
and the data line
61
and is connected to the gate line
41
and the data line
61
. A driving TFT “T
D
” is formed in the pixel region “P” and is connected to the switching TFT “T
S
”.
As stated above, the gate electrode
42
of the driving TFT “T
D
” is connected to the drain electrode of the switching TFT “T
S
” and a first capacitor electrode
45
of the storage capacitor. The source electrode
62
of the driving TFT “T
D
” is connected to the source region
22
through a first contact hole
50
a
. The source electrode
62
is also connected to the second capacitor electrode
65
of the storage capacitor, and the second capacitor electrode
65
is connected to the power line
67
. The second capacitor electrode
65
forms the storage capacitor with the overlapped first capacitor electrode
45
. A drain region
23
of the driving TFT “T
D
” overlaps a pixel electrode
81
formed in the pixel region “P”, and the drain region
23
is connected to the pixel electrode
81
through a second contact hole
50
b.
FIG. 3
illustrates a cross-section along the line III—III of FIG.
2
. In
FIG. 3
, polycrystalline silicon layers
21
,
22
and
23
having an island shape are formed on a substrate
10
, and the polycrystalline silicon layers are divided into an active layer
21
and source and drain regions
22
and
23
. The source and drain regions
22
and
23
are doped.
A gate insulator
30
is formed on the polycrystalline silicon layers
21
,
22
and
23
, and a gate electrode
42
and a first capacitor electrode
45
are formed on the gate insulator
30
. The gate electrode
42
is disposed over the active layer
21
.
An interlayer dielectric
50
is formed on the gate electrode
42
and the first capacitor electrode
45
, and the interlayer dielectric
50
has first and second contact holes
50
a
and
50
b
, which also pass through the gate insulator
30
, to expose the source and drain regions
22
and
23
, respectively.
A source electrode
62
and a second capacitor electrode
65
are formed on the interlayer dielectric
50
. The source electrode
62
and the second capacitor electrode
65
are made of a conductive material such as metal. The source electrode
62
is connected to the source region
22
through the first contact hole
50
a
. The second capacitor electrode
65
contacts the source electrode
62
, and overlaps the first capacitor electrode
45
to form a sto
Ahn Tae-Joon
Park Jae-Yong
LG. Philips LCD Co. Ltd.
McKenna Long & Aldridge LLP
Philogene Haissa
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