Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2001-09-27
2003-02-25
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S504000
Reexamination Certificate
active
06525467
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an organic electroluminescence display device (which may be referred to as an organic EL display device), and a method of producing the same.
More specifically, the present invention relates to an organic EL display device having a large luminescence pixel area to be suitable for display devices (displays) for the personal use and industrial use; and a production method making it possible to obtain such an organic EL display device effectively.
BACKGROUND ART
Conventionally, there have been suggested EL display devices wherein EL elements, each of which is composed of a luminescent layer sandwiched between electrodes, are driven (are caused to cause luminescence) through scanning electrode lines or signal electrode lines arranged in a matrix form. To make their luminescence pixels highly fine, it is required to prevent a voltage drop and a response delay based on the wiring resistance of the scanning electrode lines and the like.
As shown in
FIG. 17
, therefore, there is suggested an inorganic EL element comprising first transparent electrodes (lower electrodes)
102
, an inorganic luminescent layer
104
and second electrodes (opposed electrodes)
105
which are successively deposited on a glass substrate
101
, wherein auxiliary electrodes
103
for resistance-reduction and the first transparent electrodes
102
are electrically networked to each other on the same plane and they are electrically connected to each other in side ends of the first transparent electrodes
102
and non-luminescent portions.
One of EL elements having this type of auxiliary electrode is an EL element disclosed in Japanese Patent Application Laid-Open (JP-A) No. 1996-180974.
As shown in
FIG. 18
, JP-A No. 1999-31590 suggests an organic EL element wherein metal electrodes
203
are formed, in the vicinity (non-luminescent portions) of transparent electrodes
202
formed in a simple matrix form on a substrate
201
, so as to overlap with four sides of the respective transparent electrodes
202
to connect them electrically, and the metal electrodes
203
are covered with an electric insulation layer
206
, thereby suppressing the electric resistance of the transparent electrodes
202
by the metal electrodes
203
.
On the other hand, as shown in
FIG. 19
, WO97/34447 discloses an organic EL element comprising a flattening layer
306
, lower electrodes
302
, an organic luminescent layer
304
and opposed electrodes
305
which are successively deposited on a supporting substrate
301
, wherein an auxiliary wiring layer
303
which is electrically connected to the lower ends of the lower electrodes
302
is formed and the auxiliary wiring layer
303
is embedded in the flattening layer
306
.
In the EL element shown in
FIG. 17
, however, the first transparent electrodes (lower electrodes) and the auxiliary electrodes are arranged on the same plane and they are electrically connected to each other in the state that they overlap with each other. Moreover, the luminescent layer is deposited directly on the transparent electrodes and the auxiliary electrodes. For these reasons, many level-differences, which result from the film thicknesses of the transparent electrodes and the auxiliary electrodes, are generated. Therefore, there arises a problem that crosstalk, which is a phenomenon of luminescence of pixels other than selected pixels, is caused by a short circuit between some opposed electrode and some lower electrode, or a problem that display defects, such as generation of a non-luminescence line, which is a phenomenon that light from selected pixels is not emitted by the snapping of the opposed electrode, are easily generated.
Since the transparent electrodes and the auxiliary electrodes are formed on the same plane, the sectional area of the auxiliary electrodes themselves is so small that sufficient measures cannot be taken for making the luminescence pixels highly fine. Particularly in the case that the luminescence pixels are made highly fine to make the electric resistance of the transparent electrodes to, for example, 1 k&OHgr; or more, it is not easy to adjust the electric resistance of the transparent electrodes to a low value, for example, 100&OHgr; or less by changing the width or the thickness of the auxiliary electrodes.
Furthermore, the transparent electrodes and the auxiliary electrodes are formed on the same plane. Therefore, if the transparent electrodes and the auxiliary electrodes are subjected to positional slippage, the transparent electrodes adjacent to the auxiliary electrode subjected to the positional slippage are short-circuited through this auxiliary electrode so that a display defect is generated. Thus, a problem that the yield in production is lowered arises.
In the case of the organic EL element shown in
FIG. 18
, the problem that the transparent electrodes are short-circuited by the positional slippage of the metal electrodes can be avoided since the metal electrodes are covered with the electric insulation layer. However, the metal electrodes wired on the same plane where the transparent electrodes are wired are formed to overlap with the edge sides of the transparent electrodes. Therefore, the level-differences resulting from the thicknesses or deposition heights of the transparent electrodes and the metal electrodes become more notable so that a short circuit is caused between some transparent electrode and some opposed electrode. Thus, there arises a problem that crosstalk and display defects such as generation of a non-luminescence line is more easily caused than the case of the EL element shown in FIG.
17
.
Furthermore, in the case of this organic EL element, the metal electrodes are made, on the same plane where the transparent electrodes are made, so as to connect electrically only to the four sides of the transparent electrodes, which do not produce an effect on the luminescent area of the EL element. However, the transparent electrodes are covered with the metal electrodes. Therefore, if the sectional area of the metal electrodes is made large, a problem that the luminescent area is reduced is caused, resulting in a problem that a luminescent brightness cannot be sufficiently obtained if the luminescence pixels are made highly fine.
On the other hand, in the organic EL display device disclosed in the PCT WO97/3447 publication, the auxiliary wiring layer is embedded in the flattening layer or the like; therefore, the level-differences resulting from the thickness of the auxiliary wiring layer is not generated and the following advantages are produced: the yield in production is high, and crosstalk and display defects such as generation of a non-luminescence line are not caused very much. However, the electrical connection portion between the auxiliary wiring layer and the lower electrode is positioned at the side end of the lower electrode; therefore, it is difficult to make the sectional area of the auxiliary electrode large. If the sectional area is made large, a problem that the area of the luminescence pixels is reduced arises.
Thus, the inventors of the present invention made eager investigations on the above-described problems. As a result, the inventors have found that the problems in the prior art can be solved by wiring a part of the auxiliary wiring layer on a face different from the face on which the lower electrodes are wired and connecting the auxiliary wiring layer electrically in non-luminescent portions in the organic EL display device, or by arranging an electric insulation layer between the lower electrodes and the auxiliary wiring layer and thus connecting the auxiliary wiring layer electrically in non-luminescent portions even if the auxiliary wireing layer and the lower electrodes are wired on the same plane.
That is, an object of the present invention is to provide an organic EL display device which has a luminescence pixel area and a high luminescent brightness, and makes it possible to exclude bad effects, such as generation of display defects based on the thickness of an auxiliary wir
Eida Mitsuru
Fukuoka Kenichi
Clove Thelma Sheree
Idemitsu Kosan Co. Ltd.
Parkhurst & Wendel, L.L.
Patel Ashok
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