A black matrix having an opening at pixels of a matrix array in a display area, a common wire including common pads and common signal lines, and gate pads in a peripheral area, and an alignment key in outer area to align interlayer thin films are formed on an insulating substrate. The process selects a set of evenly spaced distinct time points and a set of reference time points. The top wall partially encloses the body so as to create a hollow body structure that includes an interior compartment defined by the end walls, side walls, and top wall. A thickness of a part of the horizontal rib, which is connected to the outer wall portion, is set larger than a thickness of a part of the horizontal rib, which is connected to the inner wall portion.