Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2002-06-10
2004-09-28
Garrett, Dawn (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C428S212000, C313S504000, C313S506000
Reexamination Certificate
active
06797414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic EL (Electroluminescence) device and a method of manufacturing the organic EL device, and more particularly, relates to the organic EL device including metallic oxide at an interface between an organic layer including an organic luminescent layer at least and a cathode and the method of manufacturing the organic EL device.
The present application claims priority of Japanese Patent Application No. 2001-174444 filed on Jun. 8, 2001, which is hereby incorporated by reference.
2. Description of Related Art
As one of EL elements used for a display device for an information apparatus or a like, an organic EL device is developed.
FIG. 12
is a sectional view showing a structure of a conventional well-known organic EL device. The organic EL device, as shown in
FIG. 12
, is provided with a transparent insulation substrate
51
made of a glass substrate or a like, an anode (lower electrode)
52
made of transparent conductive material such as an ITO (Indium Tin Oxide) formed on the transparent insulation substrate
51
, a hole transport layer
53
formed on the anode
52
, an organic luminescent layer
54
formed on the hole transport layer
53
, a cathode (upper electrode)
55
made of AlLi (Aluminum Lithium) or a like formed on the organic luminescent layer
54
, and a cap
57
attached to the transparent insulation substrate
51
on which an element main portion including the anode
52
, the hole transport layer
53
, the organic luminescent layer
54
and the cathode
55
is formed so as to cover the element main portion via seal resin
56
.
As the seal resin
56
, for example, UV (Ultra-Violet) curable resin is used, and is cured by irradiating light including UV rays to the seal resin
56
from a light source so as to seal the EL element.
In the above-mentioned organic EL device, since there are many cases in that the interface between the organic luminescent layer
54
and the cathode
55
is incomplete, an unstable defect exists from the first. The defect indicates that an impurity level caused by a grid defect or a like is formed at a position at which an interface level must be formed. With existence of the defect, a path generates in addition to a normal carrier path, and then a leak current increases. Also, there is a possibility in that the cathode
55
and the anode
52
become short-circuited. Therefore, a characteristic of the organic EL device becomes unstable, and a high rectification ratio can not be obtained. As a result, when a simple matrix drive is performed, a pixel short-circuit and a cross talk occur.
Now, conventionally, there is another well-known organic EL device in which an oxide layer is formed at an interface between an organic luminescent layer and a cathode so as to make a characteristic stable. For example, Japanese Patent Application Laid-open No. Hei 9-245968 discloses such the organic EL device. The organic EL device, as shown in
FIG. 13
, is provided with a glass substrate
61
, an anode
62
made of ITO formed on the glass substrate
61
, a hole transport material layer
63
made of an organic material formed on the anode
62
, an electron transport material layer
64
made of an organic material formed on the hole transport material layer
63
, and a cathode
65
formed on the electron transport material layer
64
. An oxide layer
66
(or a hydroxide layer) is formed at an interface between the electron transport material layer
64
and the cathode
65
.
As a material for the cathode
65
, a univalent metal such as Li (lithium), Na (sodium) and K (potassium), a bivalent metal such as Ca (calcium), and a trivalent metal such as Al (aluminum) are used. Concretely, when a film of the material of the cathode
65
is formed, the oxide layer
66
is formed by making a concentration of oxygen molecules or hydrogen molecules in an atmosphere higher than that of ordinary film formation.
With this arrangement, a work function of metals or ionization potential of organic material at the interface between the electron transport material layer
64
which is an organic luminescent layer and the cathode
65
is lowered, whereby a low voltage drive is possible. As a result, it is possible to obtain the organic EL device which operates stably.
However, in the organic EL device disclosed in Japanese Patent Application Laid-open No. Hei 9-245968, since only the oxide layer is formed at the interface between the organic luminescent layer
64
and the cathode
65
, there is a problem in that it is difficult to obtain a high rectification ratio.
In other words, in Japanese Patent Application Laid-open No. Hei 9-245968, when the film of the material of the cathode
65
is formed in manufacturing the organic EL device, the oxide layer
66
is formed by making a concentration of oxygen molecules or hydrogen molecules in the atmosphere higher than that of ordinary film formation. Therefore, since it is difficult to control the concentration of oxygen molecules or hydrogen molecules in a desirable range, a yield of manufacturing the organic EL device gets worse, a throughput lowers, and an enough high rectification ratio can not be obtained. Further, the oxide layer
66
(or the hydroxide layer) is an insulation layer, and therefore, when the oxide layer
66
(or the hydroxide layer) is formed evenly, there are problems in that a drive voltage is high and a luminescent efficiency lowers.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide an organic EL device and a method of the organic EL device capable of obtaining a high rectification ratio with a low drive voltage and capable of making a luminescent efficiency high.
According to a first aspect of the present invention, there is provided an organic EL device in which an anode made of a transparent electrode, an organic layer including an organic luminescent layer at least, and a cathode sequentially stacked on a transparent insulation substrate, the cathode including a metallic oxide in an interface with the organic layer wherein; the metallic oxide is formed so as to have a concentration gradient in which a concentration becomes high at a side of the interface with the organic layer.
In the foregoing, a preferable mode is one wherein the cathode includes a first cathode and a second cathode and the first cathode includes the metallic oxide in the interface with the organic layer.
Also, a preferable mode is one wherein the cathode includes a plurality of layers and a cathode among the plurality of layers includes the metallic oxide in the interface with the organic layer.
Also, a preferable mode is one wherein the concentration gradient of the metallic oxide varies curvedly along a direction of a film thickness of the cathode.
Also, a preferable mode is one wherein the concentration gradient of the metallic oxide varies linearly along the direction of the film thickness of the cathode.
Furthermore, a preferable mode is one wherein a concentration of the metallic oxide becomes 0 (zero) in the film thickness of the cathode forming the interface with the organic layer.
According to a second aspect of the present invention, there is provided a method of manufacturing an organic EL device in which an anode made of a transparent electrode, an organic layer including an organic luminescent layer at least, and a cathode sequentially stacked on a transparent insulation substrate, the cathode including metallic oxide in an interface with the organic layer wherein;
the transparent insulation substrate on which the anode and the organic layer are sequentially stacked is put into a vacuum evaporation apparatus, and a first metal capable of forming the metallic oxide and a second metal for forming the cathode are co-evaporated in a manner that the metallic oxide having a concentration gradient in which a concentration becomes high at a side of the interface with the organic layer is formed.
According to a third aspect of the present invention, there is provided a method of manufacturing
Garrett Dawn
McGuireWoods LLP
Samsung SDI & Co., Ltd.
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