FIG. 26B is a plan view showing the inner side surface of the upper second housing portion 102 b shown in FIG. 26A. FIG. 26C is a plan view showing an outer side surface of the upper second housing portion 102 b shown in FIG. 26A. [0223] Referring to FIGS. 26A, 26B and 26C, the conductor layer 102 bm is made of an electrically conductive material such as magnesium or zinc, and includes a rectangul