Organic electroluminescent device with color filter entirely...

Details Organic electroluminescent device with color filter entirely... Organic electroluminescent device with color filter entirely...

1999-10-19

2004-02-03

Patel, Ashok (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Solid-state type

C313S506000, C313S503000, C313S498000, C445S024000

Reexamination Certificate

active

06686692

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electroluminescent device [also referred to as “EL device” in the following], and in particular to an electroluminescent device with a flattened electroluminescent layer [also referred to as “EL layer” in the following].
2. Description of the Prior Art
FIG. 1
shows the basic structure of an organic EL device with a color filter. The organic EL device
50
includes a color filter
59
, an anode electrode
57
made of ITO, an organic EL layer
56
, and a cathode electrode
55
, formed in this order on a glass substrate
53
serving as a supporting member. The organic EL layer
56
consists of a hole transport layer
56
a
and an emitter layer
56
b
. When a predetermined voltage is applied between the anode electrode
57
and the cathode electrode
55
, the emitter layer
56
b
emits light, which is emitted through the color filter
59
and the glass substrate
53
.
FIG. 2
shows a color organic EL device
60
, whose anode electrodes and cathode electrodes are arranged in form of a matrix. The organic EL device
60
includes a plurality of color filters
64
extending in the row direction and lined up in the column direction
73
, formed on a glass substrate
63
serving as the supporting member. A plurality of anode electrodes
67
made of ITO extending in the column direction and lined up in the row direction are formed on the color filters
64
. An organic EL layer
66
extending over the entire substrate is formed on top of the anode electrodes
67
. A plurality of cathode electrodes
65
extending in the row direction and lined up in the column direction are formed on top of the organic EL layer
66
.
Selecting the anode electrodes
67
and cathode electrodes
65
to which a voltage is applied, the organic EL layer
66
emits light at the desired locations, which is transmitted through the color filter
64
and the glass substrate
63
, and emitted in the arrow direction
75
.
This organic EL device
60
, however, has the following problems. In this organic EL device
60
, the anode electrodes
67
, the organic EL layer
66
, and the cathode electrodes
65
are formed after forming the color filter
64
, because the color filter
64
, the anode electrodes
67
, the organic EL layer
66
, and the cathode electrodes
65
are formed in this order on the glass substrate
63
. Consequently, the anode electrodes
67
, the organic EL layer
66
, and the cathode electrodes
65
have to be formed under conditions that do not destroy the color filter
64
, which has already been formed. The forming conditions (such as material quality and temperatures) for those electrodes and for the organic EL layer
66
are limited to conditions that the color filter
64
can withstand. Also, because the anode electrodes
67
, the organic EL layer
66
, and the cathode electrodes
65
are formed on the color filter
64
, the surface of the color filter
64
has to be smooth.
Moreover, the organic EL layer
66
is about 100 nm thick, whereas the thickness of the color filter
64
is about 1 to 3 &mgr;m. When such a thin organic EL layer is formed on top of the color filter
64
with its sharp differences in level, there is the danger that the organic EL layer becomes thinner at corner portions of the level differences. Electric fields concentrate at the thin portions of the organic EL layer, which leads to light emission irregularities. The amount of light emitted from the organic EL layer is inversely proportional to the third power of its film thickness, so that slight variations of the film thickness have a large influence on the amount of emitted light.
SUMMARY OF THE INVENTION
With the foregoing drawbacks of the prior art in view, it is an object of the present invention to present an EL device with color filter, allowing the EL layer to be made flat.
An organic EL device of the present invention includes 1) a lower electrode formed in or on a substrate with a flat surface, 2) an organic EL layer formed on top of the lower electrode, 3) a transparent upper electrode formed on top of the organic EL layer, and 4) a color-converting layer arranged on top of the upper electrode.
The features of the present invention, other objects, uses and merits should become clearer from the following examples, with reference to the accompanying drawings.


REFERENCES:
patent: 5705285 (1998-01-01), Shi et al.
patent: 5811177 (1998-09-01), Shi et al.
patent: 5998805 (1999-12-01), Shi et al.
patent: 6008578 (1999-12-01), Chen
patent: 6037712 (2000-03-01), Codama et al.
patent: 6046543 (2000-04-01), Bulovic et al.
patent: 6117529 (2000-09-01), Leising et al.
patent: 6121726 (2000-09-01), Codama et al.
patent: 6198217 (2001-03-01), Suzuki et al.
patent: 6433355 (2002-08-01), Riess et al.
patent: 961330 (1999-12-01), None

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