FIG. 13 illustrates a spring 70 having particularly advantageous a segmental dome shape. The small arrow in the figure indicates that the center portion is spaced apart from the level of the edge portion or portions. The spring 70 operated basically the same way as described above with respect to the dome-shaped spring. The segmental dome shaped spring when not completely compressed, an edge portion or portions of the segmental dome are in contact with one of the functional multilayer structure 20 (such as the first 22 or the second substrate 28, or the molded material layer 26) and the movable member 40, and a center portion of the dome is spaced apart from the other of the functional multilayer structure 20 and the movable member 40. FIG. 13 illustrates that the edge portion is in contact with the functional multilayer structure 20. The dome-shaped spring 70 in FIG. 13 may, preferably, be of plastic material, such as of a thermoformable plastic film. The center portion of the segmental dome shaped spring may comprise the through-hole through which the movable member 40 may extend towards the functional multilayer structure 20.
