Problem To provide an inexpensive reservoir tank in which a light-out fluid level can be moved even farther away from a lead switch while reliably moving a float up and down and stabilizing the operation of the lead switch. A conductive film pattern is provided to be electrically insulated from the gate and data lines, and display electrodes, and to be overlapped on the display electrodes, thereby forming a storage capacitance between each of the display electrodes and the conductive film pattern. Some embodiments include a conductive fin, 5, to reduce cross-polarization coupling between antenna arms. Although in the preferred embodiment the plurality of surfaces defines a stair-step having right angles, other geometric patterns are applicable, so long as an irregular defect may be made more regular, andor compressive forces are used to prevent shear stress.