A display panel assembly includes a display panel including a light emitting structure and having a rectangular planar shape with rounded corners. A film layer is disposed under the display panel so as to overlap the display panel. The film layer includes a central area having a rectangular planar shape and a peripheral area surrounding the central area. In the peripheral area, the film layer has a thickness change section in which a thickness of the film layer gradually decreases and then gradually increases in a direction away from the central area.