An object of the present invention is to provide a display device for making it possible to accurately adjust a gradation current even if there is a variation in characteristics of a transistor for driving an organic EL element in a display device using an organic EL element. Reinforcement pieces overhanging on front surfaces of fastener tapes are provided on side faces of the box pin and insert pin. In a second embodiment, the binary blend has a molar composition of 30 to 60 percent R717, the remainder being R170.