Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
1999-05-14
2001-10-23
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C445S024000
Reexamination Certificate
active
06307317
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an electrode structure of an organic EL display which is constituted by using organic compounds, and which is used for an information display panel, an instrumental panel, or a display for animations or still images in home appliance and electrical components of motor vehicles and motor cycles.
Recently, considerable researches have been done on organic EL devices, and the organic EL devices are about to go into actual use. An organic EL device is a device which has a basic configuration including a transparent electrode (hole injecting electrode) of tin-doped indium oxide (ITO) etc., a thin layer of hole transporting material such as triphenyldiamine (TPD) etc. deposited by evaporation on the transparent electrode, a light emitting layer of a fluorescent material such as aluminum quinolinol complex (Alq3) on the hole transporting layer, and a metal electrode (electron injecting electrode) of a low work function metal such as Mg deposited on the hole transporting layer. Such organic EL devices have drawn public attention for its uses as a display in home appliance and electrical components of motor vehicles and motor cycles since the device is capable of producing a quite high luminance of several hundreds to several 10000 cm/m
2
by the drive voltage of about 10 V.
When a display such as a matrix type display is constituted by using such an organic EL device, wiring of the electrodes comes into question. For example, in
FIG. 3
wherein a part of a matrix display is schematically illustrated, an ITO electrode layer
5
corresponding to 1 pixel is deposited on a substrate
1
, and a passivation film
6
is deposited to surround the ITO electrode layer
5
. An organic layer
7
including a light emitting layer and electron injecting electrode layer
4
are then deposited. Such structure continues to the left direction of
FIG. 3
to constitute
1
line of matrix comprising necessary number of pixels. It should be noted that wiring on the side of the hole injecting electrode for connection of the ITO electrode layer
5
is omitted in FIG.
3
.
The structure shown in the right-hand part of
FIG. 3
is produced by depositing an underlying layer
2
and an electrode layer
3
on the substrate
1
in this order, and a part of the electron injecting electrode layer
4
extends onto the electrode layer
3
. The electron injecting electrode layer
4
and the electrode layer
3
are electrically connected at this part. The underlying layer
2
and the electrode layer
3
are connected to terminal electrode (not shown) to the right direction of
FIG. 3
to serve the role of power supply line.
When the organic EL display of such structure is produced, a hole injecting electrode structure such as the ITO layer
5
as well as the underlying layer
2
and the electrode layer
3
are first deposited, and the passivation layer
6
and the organic layer
7
, and then, the electron injecting electrode layer
4
are deposited.
FIG. 4
is a schematic cross-sectional view of the contacting part (structure shown in the right-hand part of
FIG. 3
) constituted by the underlying layer
2
, the electrode layer
3
, and the electron injecting electrode layer
4
. As shown in
FIG. 4
, the electron injecting electrode layer
4
is deposited on the underlying layer
2
and the electrode layer
3
which have been deposited beforehand for contact of the underlying layer
2
and the electrode layer
3
with the electron injecting electrode layer
4
. An oxide layer
3
a
, however, is occasionally formed by oxidation of the surface of the electrode layer
3
during the formation of the passivation layer
6
and the like as shown in FIG.
4
. As a consequence, when the electron injecting electrode layer
4
is deposited after the deposition of the organic layer
7
, contact between the electrode layer
3
and the electron injecting electrode layer
4
may become insufficient due to the high resistance of the surface portion of the electrode layer
3
, and such insufficient contact results in faulty connection and failure in the full drive of the pixels.
SUMMARY OF THE INVENTION
In view of such situation, an object of the present invention is to provide an organic EL display wherein electric connection between the electron injecting electrode layer and the electrode layer is improved, which is less likely to suffer from poor connection, and which exhibits low connection resistance. Another object is to realize a method for producing such an organic EL display.
This and other objects are achieved by the present invention which is defined below.
(1) An organic EL display having an electrode structure which connects at least a terminal and an electron injecting electrode,
wherein said electrode structure comprises
an underlying layer as a lower layer comprising a metal having low susceptibility to surface oxide layer formation, and
an electrode layer as an upper layer comprising a metal which has a susceptibility to surface oxide layer formation higher than that of the underlying layer; and
wherein said underlying layer and said electron injecting electrode layer are in direct contact with each other at least in some parts in the region where the electrode layer is connected to said electron injecting layer.
(2) An organic EL display according to the above (1) wherein the metal constituting said electrode layer has a resistivity lower than the metal constituting the underlying layer.
(3) An organic EL display according to the above (1) wherein the electron injecting electrode layer which is connected to an organic EL structure involved in light emitting function extends onto the region where said electrode layer is in contact with the electron injecting electrode layer; and the electron injecting electrode layer is electrically connected to the underlying layer in some parts thereof.
(4) An organic EL display according to the above (1) wherein a protective layer is formed on said electrode layer and said protective layer comprises a metal having a susceptibility to surface oxide layer formation lower than that of the electrode layer; and
said electron injecting electrode layer is formed on said protective layer so that the electrode layer and the underlying layer are electrically connected to the electron injecting electrode layer through the protective layer.
(5) An organic EL display according to the above (1) wherein said underlying layer comprises a material selected from titanium nitride and chromium.
(6) An organic EL display according to the above (1) wherein said electrode layer comprises a material selected from aluminum or an alloy containing aluminum as its main component.
(7) An organic EL display according to the above (4) wherein said protective layer comprises the material constituting said underlying layer.
(8) An organic EL display according to the above (1) wherein at least a part of the region where said electrode layer is in contact with said electron injecting layer is formed in the shape of a comb.
(9) An organic EL display according to the above (1) wherein said display has an organic EL structure, and the organic EL structure comprises the electron injecting electrode layer, a hole injecting electrode layer, and at least one organic layer involved in the light emitting function disposed between the electron injecting electrode layer and the hole injecting electrode layer.
(10) A method for producing an organic EL display wherein an underlying layer and an electrode layer are formed in this order for connection with the terminal electrode, and the electrode layer is formed on the underlying layer to leave a portion of the underlying layer uncovered, and wherein an electron injecting electrode layer is deposited on the resulting region where the electrode layer has been formed and the underlying layer is partly left uncovered.
(11) A method for producing an organic EL display according to the above (10) wherein a part of said electrode layer is formed in the shape of a comb to thereby leave said underlying layer partly uncovered.
REFERE
Codama Mitsufumi
Takaku Munehiro
Hopper Todd Reed
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Nimeshkumar D.
TDK Corporation
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