Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
1999-09-13
2003-03-04
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S503000, C428S917000
Reexamination Certificate
active
06528942
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention related to an organic electroluminescence device, its manufacturing method and a board used therefor, and more particularly to its pattern formation.
2. Description of the Related Art
An electroluminescence (EL) device has been used as various kinds of display devices or light sources, a back light for a liquid crystal display, a light emitting device in an optical communication device, etc. The EL device is a light emitting device using electric-field light-emission of a solid fluorescent material. It is now actually used in the form of an inorganic EL device which uses an inorganic material as a light emitting material, and being developed in various applications inclusive of a back light for the liquid crystal display, flat display, etc. However, the inorganic EL device, which requires a high voltage of 100 V or more for light emission and difficult to emit blue light, has been difficult to implement its full-color display using three RGB primary colors.
On the other hand, various studies have been also made for the EL device using an organic material. However, because of its poor efficiency of light emission, it has not been put into real practice. In recent years, the EL device having a function-separating type of a laminated structure has been proposed in which the organic material is separated into a hole transporting layer and a light emitting layer. It has been verified that the organic EL can provide high luminance at a low voltage of 10 V or lower. Since then, the organic EL device has drawn great attention. Also now, the organic EL device having a function-separating type of separation structure is being studied widely.
An explanation will be given of the structure and operation of an ordinary EL device. The EL device has a laminated structure composed of a first electrode formed on the surface of a transparent glass substrate by sputtering or resistive-heating evaporation technique, a light emitting layer formed thereon and a second electrode formed thereon by a vacuum evaporation technique. The first electrode is made of a transparent conductive material such as indium tin oxide (ITO). The light emitting layer is made of poly (2-methoxy-5-dodecyloxy-p-phenylene vinylene) (hereinafter referred to as MDOPPV). The second electrode is made of metal such as Aluminum (Al).
In operation, when a DC voltage is applied to the EL device having such a structure, holes are injected from the first electrode into the light emitting layer, and electrons are injected from the second electrode into the light emitting layer. The recombination of holes and electrons occurs in the light emitting layer. When the exitons thus created decay from an excited state to a ground state, the phenomenon of light emission occurs. A various light emission color can be obtained by changing the molecular structure of an organic compound.
Meanwhile, it is known that the property of the polymer such as MDOPPV used for this light emitting layer varies drastically by photo-oxidation. Specifically, bleaching of optical absorption is observed, which is whitening corresponding to the inter-band transition which is attributable to shortening of the effective &pgr; conjugated length and reduction of the molecular weight. In this way, extinction of photoluminescence by the photo-irradiation in the air has been studied. The light extinction is due to the defect such as a carbonyl group which operates as a light extinction center for light emission species such as exitons or exitons-polarons.
A technique of patterning the EL device using such a phenomenon has been proposed. This technique, however, performs the photo-irradiation for patterning the light-emitting layer in an atmosphere of oxygen prior to forming a second electrode. In this technique, since the second electrode must be formed after the pattern has been formed, when the substrate is heated at a high temperature in a vacuum evaporation step, the device region deteriorates greatly and the light emitting region does not emit light favorably, thus making it impossible to give sufficient contrast.
Further, there is a phenomenon that the center of light extinction is widened so that the non-light-emitting region is extended and the contour of an image is also extended.
Further, since the patterning is completed through the vacuum evaporation step starting from photo-irradiation for forming an image, it takes a long time from determination of an image to be formed to its completion. Namely, the TAT (turn around time) is disadvantageously long. Under such a circumstance, the present invention has been accomplished.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a reliable organic electroluminescence (EL) device which can provide high contrast.
A second object of the present invention is to provide a method for manufacturing an organic EL device in a short time from its order to completion and with good workability.
A third object of the present invention is to provide a reliable board for a display device which can provide high contrast.
In order to attain the first object, in accordance with a first aspect of the present invention, there is provided an organic electroluminescence device comprising: a substrate; a first electrode formed on the substrate; a light emitting layer formed on the first electrode; and a second electrode formed on the light emitting layer and made of an oxygen-transmittable material, wherein the light-emitting layer includes an oxide layer selectively formed by the selective photo-oxidation using light and oxygen reached through the second electrode, and the oxide layer constitutes (serves as) a non-light-emitting region.
In this configuration, after the second electrode is formed, light-emitting species in a local region in the light emitting layer are extinguished by selective photo-oxidation using oxygen reached through the second electrode. Therefore, a vacuum evaporation step for forming the second electrode is not required after a pattern is formed. Thus, the substrate is not heated to a high temperature and hence a device region is not deteriorated, thereby providing sufficient contrast. In addition, since the vacuum evaporation step is not carried out, a phenomenon owing to the temperature in this step, i.e. that the center of light extinction is extended, the non-light-emitting region is expanded and the contour of an image is expanded, does not occur. Further, since the patterning is completed starting from photo-irradiation for creating an image and through the vacuum evaporation, it can be implemented in a short time from determination of the image to be formed to its completion. The oxide layer may not be formed over the entire depth of the light emitting layer, but may be partially formed therein.
A second aspect of the device is an organic electroluminescence device according to the first aspect wherein the substrate is made of a light-transmittable material and the first electrode is also made of a light transmittable material; and the non-light-emitting region is formed through invasion of oxygen from the side of the second electrode and photo-oxidation based on photo-irradiation from the side of the substrate.
In this configuration, since oxygen is supplied to the light emitting layer from the side of the second electrode and photo-irradiation is done from the side of the substrate, after the pattern is formed, the second electrode is covered with a protective layer so that it is protected from transmittance of oxygen. This permits the life of the electroluminescence device to be lengthened.
A third aspect of the device is an organic electroluminescence device according to the firs aspect, wherein the second electrode is made of a light-transmittable material and the non-light-emitting region is formed by photo-oxidation using light transmitted through the second electrode.
In this configuration, since the second electrode is made of a light-transmittable material and photo-irradiation is done from the s
Onoda Mitsuyoshi
Tada Kazuya
Morgan & Lewis & Bockius, LLP
Patel Ashok
Rohm & Co., Ltd.
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