Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2000-11-09
2002-05-14
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169100
Reexamination Certificate
active
06388387
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical element including an organic light emitting layer and an organic EL (electroluminescence) display having organic electroluminescent elements.
2. Description of the Related Art
According to an organic EL display having a number of pixels each constituted by an organic electroluminescent element (hereinafter, referred to as organic EL element), voltage is applied to each of the organic EL elements, electrons are injected from a cathode thereof and holes are injected from an anode thereof respectively to an organic light emitting layer and light is emitted by causing recombination of electrons and holes in the organic light emitting layer.
As such an organic EL element provided to an organic EL display, for example, there is a single hetero-structure type organic EL element shown by FIG.
9
. According to the organic EL element, an anode
2
comprising a transparent conductive film made of ITO (Indium tin oxide) or the like is provided on a transparent substrate
1
of a glass substrate or the like, on which an organic layer
5
comprising a hole transport layer
3
and a light emitting layer
4
and a cathode
6
made of aluminum or the like are provided in this order.
Further, according to the EL element constituted in this way, when positive voltage is applied to the anode
2
and negative voltage is applied to the cathode
6
, holes injected from the anode
2
reach the light emitting layer
4
via the hole transport layer
3
and electrons injected from the cathode
6
reach the light emitting layer
4
, respectively and recombination of electrons and holes is caused in the light emitting layer
4
. At this occasion, light having a predetermined wavelength is generated and is emitted from a side of the transparent substrate
1
to outside as shown by arrow marks in FIG.
9
.
Accordingly, by arranging a number of the organic EL elements in, for example, a matrix-like shape, an organic EL display is formed as mentioned above.
FIG. 10
shows an example of such a conventional organic EL display. The organic EL display shown by
FIG. 10
is constituted such that a plurality of transparent electrodes
8
in a stripe-like shape (band-like shape) are provided on a transparent substrate
7
, an organic layer
9
in a sheet-like shape constituted by laminating a hole transport layer and a light emitting layer are provided on the transparent electrodes
8
and a plurality of cathodes
10
in a stripe-like shape (band-like shape) are provided on the organic layer
9
to be orthogonal to the transparent electrodes
8
and organic EL elements are formed at positions where the transparent electrodes
8
and the cathodes
10
intersect with each other.
FIG. 11
is a view showing other example of a conventional organic EL display. The organic EL display shown by
FIG. 11
is constituted such that the transparent electrodes
8
in a stripe-like shape are provided as anodes on the transparent substrate
7
, organic layers
11
a,
11
b
and
11
c
in a stripe-like shape each comprising a hole transport layer and a light emitting layer are provided on the transparent electrodes
8
in a state in which the organic layers and the transparent electrodes
8
are orthogonal to each other and cathodes
12
in a stripe-like shape having dimensions substantially equal to dimensions of the organic layers
11
a,
(
11
b
and
11
c
) are provided on the organic layers,
11
a,
11
d
and
11
c.
In this case, each of the organic layers
11
a,
11
b
and
11
c
is provided with a light emitting characteristic in correspondence with one of red (R), green (G) and blue (B) by which the organic EL display constitutes a display of full color or multiple color.
An explanation will be given of image display by the color organic EL display shown by FIG.
11
. According to the color organic EL display, as shown by
FIG. 12
, a scanning circuit
13
is connected to the transparent electrodes
8
and a brightness signal circuit
14
is connected to the cathodes
12
. Further, the organic layers
11
a,
11
b
and
11
c
respectively emit light by time-sequentially applying signal voltages to the organic layers
11
a,
11
b
and
11
c
at positions intersecting with the transparent electrodes
8
and the cathodes
12
by the scanning circuit
13
and the brightness signal circuit
14
. Accordingly, the organic EL display functions as an image reproducing apparatus by such a control.
However, there is the following inconvenience in the organic EL display.
In the case in which the organic EL display is driven by, for example, the simple matrix system, when a number of scanning lines is several hundreds, in order to ensure sufficient brightness, current of about 1 A/cm
2
need to flow. Then, in this case, although it differs depending also on the size of the display, current of about 0.5 through 1 A is flowed instantaneously in the transparent electrodes
8
connected to the scanning circuit
13
.
Further, the resistance value of ITO which is normally used for the transparent electrode
8
is about 100 times as much as that of a metal of aluminum or the like and its alloy. Accordingly, when large current of about 0.5 through 1 A is flowed as mentioned above, voltage drop in the transparent electrode
8
is increased. Further, when such a large voltage drop is caused in the transparent electrode
8
, voltage applied on the respective organic EL elements in the organic EL display becomes nonuniform and the display function of the organic EL display is significantly deteriorated.
That is, when the organic EL display is driven by the simple matrix system, although depending also on the display size, current flowing in the electrodes on the scanning side becomes 100 through 1000 times as much as current flowing in the electrodes on the brightness signal side in view of the drive principle. However, in the case of the organic EL display, large current is flowed in the transparent electrode
8
having high resistance. Therefore, large voltage drop is caused in a transparent conductive film constituting the transparent electrode
8
. Voltage applied on the organic layers
11
a,
11
b
and
11
c
constituting the respective pixels becomes nonuniform by which the display function is deteriorated and power consumption in the transparent electrode
8
is increased.
Further, in the case of the color organic EL display shown by
FIG. 11
, the organic layers
11
a,
11
b
and
11
c
are formed over an entire lower face thereof along the length direction of the cathodes
12
formed in a stripe-like shape. Owing to such a structure, brightness signals necessary for respective colors of R, G and B must be provided from the cathodes
12
. Therefore, the brightness signal circuit
14
must be connected to the cathodes
12
and the scanning circuit
13
must be connected to the transparent electrodes
8
.
Further, as mentioned above, power consumed in the transparent electrodes
8
is increased and accordingly, low power consumption formation in the entire organic EL display is deteriorated. Accordingly, to provide the organic EL display having low power consumption, the resistance of electrodes on the scanning side needs to reduce to thereby reduce voltage drop.
As a measure for reducing the resistance of the scanning side electrodes, there is disclosed a technology in which metal wirings are installed along with the transparent electrodes in JP-A-5-307997. According to the technology, a metal having low resistance is provided at a portion between the transparent electrode and the organic layer to thereby achieve low resistance formation of the scanning electrode.
However, in order to achieve sufficient low resistance formation by such a technology, an area of the metal wiring provided along with the transparent electrode needs to magnify as large as possible. When the area of the metal wiring is magnified in such a manner, the metal wiring covers the organic layers
11
a,
11
b
and
11
c
constituting light emitting portions, as a result, the l
Hirano Takashi
Nakayama Tetsuo
Sano Naoki
Sasaoka Tatsuya
Sekiya Mitsunobu
Dinh Trinh Vo
Sonnenschein Nath & Rosenthal
Wong Don
LandOfFree
Optical element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2874161