A flat display device, comprising: a substrate having an rectangular shape and including an image display unit on which display devices are arranged, wherein organic light emitting diodes are arranged in the image display unit of the substrate and the organic light emitting diodes include a lower electrode, an organic thin film layer, and an upper electrode; a sealing member with an attached absorbent adapted for absorbing moisture or oxygen contained in the air between the substrate and the sealing member; wherein the sealing member is sealed to the substrate with a sealant, the sealant including a frame portion consisting of four bar shaped frame members arranged such to form an rectangle which surrounds the image display unit, wherein the substrate comprises a top surface and the sealing member includes a substrate, and the sealant consists of one material which is selected from the group consisting of a thermosetting resin, an ultraviolet setting resin, and a thermoplastic resin, and wherein the frame portion of the sealant comprises a cross-section having a rectangular shape, and an upper surface of the frame portion is bonded to the substrate of the sealing member and a lower surface of the frame portion is bonded to the top surface of the substrate, characterized in that the sealant further comprises four protrusion portions adapted for preventing the separation from the sealing member of the substrate at corners of the substrate, wherein the protrusion portions are protruding from the frame portion at corners of the substrate, wherein the protrusion portions are arranged at each corner of the four bar shaped frame members, and wherein each protrusion portion comprises first and second bar pattern shaped parts protruding from corners of the frame portion. a substrate having an rectangular shape and including an image display unit on which display devices are arranged, wherein organic light emitting diodes are arranged in the image display unit of the substrate and the organic light emitting diodes include a lower electrode, an organic thin film layer, and an upper electrode; a sealing member with an attached absorbent adapted for absorbing moisture or oxygen contained in the air between the substrate and the sealing member; wherein the sealing member is sealed to the substrate with a sealant, the sealant including a frame portion consisting of four bar shaped frame members arranged such to form an rectangle which surrounds the image display unit, wherein the substrate comprises a top surface and the sealing member includes a substrate, and the sealant consists of one material which is selected from the group consisting of a thermosetting resin, an ultraviolet setting resin, and a thermoplastic resin, and wherein the frame portion of the sealant comprises a cross-section having a rectangular shape, and an upper surface of the frame portion is bonded to the substrate of the sealing member and a lower surface of the frame portion is bonded to the top surface of the substrate, characterized in that the sealant further comprises four protrusion portions adapted for preventing the separation from the sealing member of the substrate at corners of the substrate, wherein the protrusion portions are protruding from the frame portion at corners of the substrate, wherein the protrusion portions are arranged at each corner of the four bar shaped frame members, and wherein each protrusion portion comprises first and second bar pattern shaped parts protruding from corners of the frame portion.