A flexible printed circuit board is pulled out to the outside from an end portion of the bottom surface portion. A notch is formed on a tip end of the end portion of the bottom surface portion such that an inner edge of the notch and an outer edge which projects from the notch are contiguously formed. A side of the flexible printed circuit board is arranged so as to overlap the notch. The outer edge of the bottom surface portion which projects overlaps the flexible printed circuit board. An angle made by a straight line which connects an intersecting point between the side of the flexible printed circuit board and the inner edge and a point of inflection between the inner edge and the outer edge and the side of the flexible printed circuit board is set to 45° or less.