PURPOSE: To prevent reliability of a function from worsening due to wearing dust and chipping pieces by smooth-processing the reference surface of a positioning pad by calender polishing work or the like, so as to prevent a position change of the reference surface from being generated due to wearing or the like during the use.

CONSTITUTION: In a funnel 2, between itself and a faceplate, in order to obtain a reference surface 5a for assembling position alignment in the case of applying a frit seal, a positioning pad 5 is protruded to be integrally molded in three parts of a peripheral edge part. In the reference surface 5a, its surface is smoothly processed by mechanical polishing, chemical process of using hydrofluoric acid, silica sol coating, etc. An edge part 5b in the periphery of the reference surface 5a is applied with chamfering work to provide roundness. Thus in a frit seal process, by suppressing the reference surface from wearing in the case that the pad reference surface is brought into contact with a supporting member in an assembly jig side, connection can be performed always in a fixed reference position.