Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-12-27
2004-06-01
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169100, C257S753000, C257S762000, C345S076000
Reexamination Certificate
active
06744217
ABSTRACT:
The present invention claims the benefit of the Korean Patent Application No. 2001-89298 filed in Korea on Dec. 31, 2001, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic electro luminescence device, and more particularly, an organic electro luminescence device with low-resistance wiring.
2. Description of the Background Art
An organic electro luminescence display using an electro-luminescence (EL) device is seen as the next generation display device after the cathode ray tube (CRT) and a liquid crystal display (LCD). Its applicability is wide spread and an EL device is used as a display in devices such as portable terminals, car navigation systems (CNS), game machines, notebook computers, and wall-type televisions. Generally, an organic electro luminescence display includes a matrix of electro luminescence devices each including an organic emitting layer positioned between a positive electrode and a negative electrode. Light is emitted from the organic emitting layer when a voltage is applied across the positive electrode and the negative electrode.
More specifically, the positive electrode is formed by sputtering indium-tin-oxide (ITO) on a glass substrate having switching and drive circuits and then patterning the ITO such that the electrode is connected to a drive circuit. An organic emitting layer including a hole transport layer, an emitting layer, and an electron transport layer are then formed on the ITO film. A negative electrode is then formed on the organic emitting layer. The negative electrode is a metal having low work function so as to readily supply electrons to the organic emitting layer. The ITO of the positive electrode has a high electrical conductivity so that holes can be readily supplied to the organic emitting layer. Further, the ITO has high light transmittance so that light emitted from the organic emitting layer can be transmitted through the positive electrode. Thus, when positive and negative voltages are applied to the positive electrode and to the negative electrode, respectively, the holes injected from the positive electrode and the electrons injected from the negative electrode cause the organic emitting layer to emit light.
In an organic electro luminescence display, unit pixels each containing an organic emitting layer are disposed in a matrix form. The organic emitting layers of the unit pixels are selectively driven through thin film transistors disposed in each of the respective unit pixels to display an image. The organic electro luminescence display described above will be described in more detail with reference to accompanying
FIG. 1
showing an equivalent circuit for configuring and operating the thin film transistors in accordance with a voltage driving method.
As shown in
FIG. 1
, each unit pixel includes a first thin film transistor
10
and a second thin film transistors
20
, and an organic luminescence device
30
. The unit pixel is defined by a gate line Gn for supplying a gate signal to the gate of the first thin film transistor
10
in a row direction, a data line Dm for supplying a data signal to the source of the first thin film transistor
10
in a column direction, a power line Pm for supplying electric power to the source of the second thin film transistor
20
in a column direction and a gate line of another pixel area in a row direction. The first thin film transistor
10
includes a gate electrode
11
connected to the gate line Gn to be supplied with the gate signal, a source electrode
12
connected to the data line Dm to be supplied with the data signal, and a drain electrode
13
connected to a gate electrode
21
of the second thin film transistor
20
. The second thin film transistor
20
includes the gate electrode
21
connected to the drain electrode
13
of the first thin film transistor
10
, a drain electrode
22
connected to a pixel electrode, and a source electrode
23
connected to the power line Pm. The organic luminescence device
30
includes an organic emitting layer
31
positioned between a cathode electrode (not shown) and an anode electrode (not shown), wherein the organic emitting layer
31
includes a hole transport layer (not shown), an emitting layer (not shown), and an electron transport layer (not shown). In addition, a capacitor
40
is included in which one electrode is connected to the power line Pm and the other electrode is connected both to the drain electrode
13
of the first thin film transistor
10
and to the gate electrode
21
of the second thin film transistor
20
.
Hereinafter, the operation of the equivalent circuit for the unit pixel of the organic electro luminescence display device shown in
FIG. 1
will be described in detail as follows. When the gate signal is applied to the gate electrode
12
from the gate line Gn, the first thin film transistor
10
is turned on, and therefore, the data signal supplied from the data line Dm is supplied to the gate electrode
21
of the second thin film transistor
20
through the source electrode
12
and the drain electrode
13
of the first thin film transistor
10
. Thus, the potential of the gate electrode
21
becomes the same as that of the data line Dm.
The degree of turn on for the second thin film transistor
20
is decided by the potential supplied to the gate electrode
21
, and therefore, electric current corresponding to the potential supplied to the gate electrode
21
is supplied to the organic luminescence device
30
from the power line Pm. The organic luminescence device
30
emits light according to the amount of electric current supplied. Thus, the brightness of the light emitted from the organic luminescence device
30
is determined by the value or voltage of the data signal, which is applied through the data line Dm.
Generally, in a display device having a matrix form, a gate signal is supplied to the first gate line and then to the rest of the gate lines sequentially such that an image is displayed on the screen after the sequence is completed across the display. The capacitor
40
in a unit pixel stays charged to the potential of the data signal to maintain the luminescence of the organic luminescence device
30
in the unit pixel until another data signal is supplied corresponding to another gate signal from the gate line Gn of the unit pixel. Thus, the amount of light from each unit pixel can be changed each time a gate signal is sequentially applied across the display to all of the gate lines Gn.
FIG. 2
depicts an equivalent circuit diagram of an organic electro luminescence device for configuring and operating the thin film transistors according to a current driving method. As shown in
FIG. 2
, a unit pixel includes a first thin film transistor
210
and a second thin film transistors
220
for switching, a third thin film transistor
230
and a fourth thin film transistor
240
for driving, and an organic luminescence device
250
. The area of the unit pixel is divided by gate line Gn for supplying a gate signal to the unit pixel, and is in between the data line Dm for supplying the data signal to the unit pixel and the power line Pm for supplying electric power to the source of the fourth transistor
240
of the unit pixel.
When a gate signal is supplied from the gate line Gn, the first switching thin film transistor
210
is turned on, and therefore, the data signal supplied from the data line Dm is supplied to the source electrode
232
and to the gate electrode
231
of the third thin film transistor
230
through the source electrode
212
and drain electrode
213
of the first thin film transistor
210
. At the same time, the gate signal is also applied to the gate electrode
221
of the second thin film transistor
220
from the gate scan line Gn such that the second thin film transistor
220
is also turned on. The amount of current flowing through the drain electrode
233
and the source electrode
232
of the third thin film transistor
230
from the power line Pm is determined by
LG.Philips LCD Co. , Ltd.
Philogene Haissa
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