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  Organic electroluminescent deviceUSPTO Application #: 20080107798Title: Organic electroluminescent device Abstract: An organic electroluminescent device comprises a substrate that supports a first electrode, a second electrode, and a light emitting structure that is disposed between the first and second electrodes. A protective structure comprising a layer of boron oxide and an inorganic barrier layer cooperates with the substrate to encapsulate the first electrode, the second electrode, and the light-emitting structure. (end of abstract) Agent: 3m Innovative Properties Company - St. Paul, MN, US Inventors: Fred B. McCormick, Manoj Nirmal, George V. Tiers USPTO Applicaton #: 20080107798 - Class: 427066000 (USPTO) Related Patent Categories: Coating Processes, Electrical Product Produced, X-radiation Properties, Electroluminescent Lamp The Patent Description & Claims data below is from USPTO Patent Application 20080107798. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. Ser. No. 10/948,011, filed Sep. 23, 2004, the disclosure of which is incorporated by reference in its entirety herein. TECHNICAL FIELD [0002] This invention relates to improved organic electroluminescent devices and, more particularly, to organic electroluminescent devices that have been protected to reduce the absorption of moisture by the device. This invention also relates to a method of protecting an organic electroluminescent device against the undesirable absorption of moisture by the device. BACKGROUND [0003] Organic electroluminescent devices (e.g., organic light emitting diodes) are useful in a variety of lighting applications and in the preparation of high and low resolution displays. These devices typically include an organic electroluminescent material disposed between an anode and a cathode. The devices may also contain moisture-reactive electrode materials or electroluminescent materials and susceptibility of organic light emitting diodes (OLEDs) to moisture degradation is well known. Consequently, organic electroluminescent devices that contain reactive materials are usually encapsulated to extend the useful lifetimes of the devices. Encapsulation typically involves positioning and sealing the electrodes and electroluminescent material between two substrates such as glass and polymeric materials or between a substrate and a metal can and often in the presence of a desiccant. Various other protective layers can also be included to further reduce contact of the reactive materials with moisture. SUMMARY OF THE INVENTION [0004] In one embodiment, the invention provides an organic electroluminescent device that comprises a low moisture permeable substrate (e.g., glass, metal, silicon, or a protected polymeric film) that supports a first electrode, a second electrode, and a light emitting structure that is disposed between the first and second electrodes; and a protective structure that cooperates with the substrate to encapsulate the first electrode, the second electrode, and the light-emitting structure. The protective structure comprises a layer of boron oxide and an inorganic barrier layer. Preferably, the inorganic barrier layer has low moisture permeability. [0005] The layer of boron oxide may be disposed over the first electrode, the second electrode, and the light-emitting structure, and the inorganic barrier layer may be disposed over the layer of boron oxide. The inorganic barrier layer preferably comprises an inorganic oxide, boride, nitride, carbide, oxynitride, oxyboride, or oxycarbide, such as silicon or aluminum oxides, nitrides or carbides; diamond-like carbon compounds; and metals such as silicon, aluminum or combinations thereof. Specific examples include silicon oxide (monoxide or dioxide), silicon nitride, aluminum oxide or silicon aluminum oxide. The inorganic barrier layer may be a multilayer construction comprising, for example, alternating polymeric and inorganic layers. [0006] The device may additionally comprise a buffer layer to protect the layer of boron oxide from reaction with the first electrode, the second electrode, and/or the light-emitting structure. The buffer layer may be disposed over the first electrode, the second electrode, and the light-emitting structure, the layer of boron oxide may be disposed over the buffer layer, and the inorganic barrier layer may be disposed over the layer of boron oxide. The buffer layer preferably comprises an organometallic compound or a chelate compound such as tris(8-hydroxyquinoline) aluminum (AlQ) or copper phthalocyanine (CuPc). [0007] The protective structure may additionally comprise a second inorganic barrier layer. In such constructions, a buffer layer (if present) is disposed over the first electrode, the second electrode, and the light-emitting structure, the inorganic barrier layer is disposed over the buffer layer, the layer of boron oxide is disposed over the inorganic barrier layer, and the second inorganic barrier layer is disposed over the layer of boron oxide. [0008] In another embodiment, the invention relates to a method of protecting an organic electroluminescent device. The method comprises providing an organic electroluminescent assembly comprising a low moisture permeable substrate that supports a first electrode, a second electrode, and a light emitting structure disposed between the first and second electrodes; and applying a protective structure that cooperates with the substrate to encapsulate the first electrode, the second electrode, and the light-emitting structure. The protective structure comprises a layer of boron oxide and an inorganic barrier layer. [0009] The layer of boron oxide may be applied by thermal evaporation, the inorganic barrier layer may be applied by vapor deposition, and if the device additionally comprises a buffer layer, it may be applied by either thermal evaporation or vapor deposition. BRIEF DESCRIPTION OF THE DRAWINGS [0010] The invention will be more fully appreciated with reference to the following non-limiting and not-to-scale drawings in which the same reference symbols designate like or analogous components throughout and in which: [0011] FIG. 1 is a schematic, sectional view of a first embodiment of an organic electroluminescent device according to the invention; [0012] FIG. 2 is a schematic, sectional view of a second embodiment of an organic electroluminescent device according to the invention; [0013] FIG. 3 is a schematic, sectional view of a third embodiment of an organic electroluminescent device according to the invention; [0014] FIG. 4 is a schematic sectional view of a first embodiment of a protected polymeric film that may be used as a low moisture permeable substrate in an organic electroluminescent device according to the invention; [0015] FIG. 5 is a schematic sectional view of a second embodiment of a protected polymeric film that may be used as a low moisture permeable substrate in an organic electroluminescent device according to the invention; [0016] FIG. 6 is a schematic sectional view of a third embodiment of a protected polymeric film that may be used as a low moisture permeable substrate in an organic electroluminescent device according to the invention; [0017] FIG. 7 is a schematic sectional view of a fourth embodiment of a protected polymeric film that may be used as a low moisture permeable substrate in an organic electroluminescent device according to the invention; [0018] FIG. 8 is a schematic sectional view of a fifth embodiment of a protected polymeric film that may be used as a low moisture permeable substrate in an organic electroluminescent device according to the invention; and [0019] FIG. 9 is a schematic sectional view of a sixth embodiment of a protected polymeric film that may be used as a low moisture permeable substrate in an organic electroluminescent device according to the invention. 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