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US 5,457,565 AGranted
Organic electroluminescent device
AssigneePioneer Electronic Corporation
InventorsTohru Namiki, Hitoshi Sato, Kenichi Nagayama, Teruichi Watanabe
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AssigneePioneer Electronic Corporation
InventorsTohru Namiki, Hitoshi Sato, Kenichi Nagayama, Teruichi Watanabe
Estimating the term…
An organic electroluminescent device comprises an anode, a positive-hole transport layer made of an organic compound, an emitting layer made of an organic compound, and a cathode which are layered in sequence, further comprising an electron-injecting layer containing at least one of alkaline earth metal oxides and disposed between the emitting layer and the cathode. This device emits light at a high luminance and a high efficiency upon application of a low voltage together with reduction of the decrement of luminance in the running of emitting light of the device. Selection scope for cathode materials is expanded because of the device is free from the restriction of a low work function for the cathode layer. The cathode can be made a transparent electrode such as ITO. Anode and cathode lines may be formed with low resistance material. As a result, emitting efficiency and life time of the device is improved.
An organic EL device comprising:
An electroluminescent (EL) device, comprising:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
Electroluminescent light sources: light sources with substantially two-dimensional [2D] radiating surfaces
Light sources with substantially two-dimensional [2D] radiating surfaces: characterised by the chemical or physical composition or the arrangement…
Characterised by the composition or arrangement of the conductive material used as an electrode: of translucent electrodes
Carrier injection layers: electron injection layers
Term ended 18 Nov 2013 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Field of the invention
The present invention relates to an electroluminescent device (hereinafter referred as "EL device") having an emitting layer made of an emitting substance, which utilizes an electroluminescence phenomenon that is the emission of light resulting from application of an electric field or electrons to the substance. More particularly, it is concerned with an organic EL device in which the emitting layer is made of an organic luminous substance.
2. Description of the prior art
FIG. 1 is a schematic diagram showing an organic EL device with two-layer structure;
FIG. 2 is a schematic diagram showing an organic EL device with three-layer structure;
FIG. 3 is a schematic diagram showing an organic EL device of an embodiment according to the present invention with two-layer structure;
The embodiments according to the present invention will be described in more detail with reference to the accompanying drawings.
The EL device in accordance with the present invention has the two-layer structure formed by layering an anode 2, a positive-hole transport layer 4 of organic compound, an emitting layer 3 of organic compound, an electron injecting layer 10 and a cathode 1 in sequence on a glass substrate 6 (FIG. 3). Alternatively, another EL device in accordance with the present invention has the three-layer structure formed by layering an anode 2, an organic positive-hole transport layer 4, an organic emitting layer 3, an organic electron transport layer 5, an electron injecting layer 10 and a cathode 1 in sequence on a glass substrate 6 (FIG. 4).
The electron-injecting layer 10 comprises at least one of oxides of alkaline earth metal (Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra)), for example, SrO, CaO, BaO, (Sr,Ca,Ba)O. The electron-injecting layer 10 is transparent and has a low work function of about 1.2 eV. Although the electron-injecting layer functions as an insulator, the device using this layer emits light at a high luminance only by optimize the thickness of the injecting layer. Therefore, the order of the function layers 3, 4, 5 on the substrate is various. In other words, since the electron-injecting layer 10 is used only for the first function the first and the second functions of the cathode, its interposition expands the selectional variety of materials for the electrode layers.