| 摘要 |
PROBLEM TO BE SOLVED: To provide the subject insulating substrate preventing the separation of a formed membrane after cooling and enhanced in yield and productivity in a membrane forming process. SOLUTION: An insulating substrate is constituted of the projection 22 for a common electrode formed on the surface of an alumina substrate 21 by a thick film process, projected glaze glass layers 24a1, 24a2 having the projection 22 as apexes and the glaze glass layers 24a, 24b formed on the alumina substrate 21. In this case, if the lower part of each of the projected glaze glass layers 24a1, 24a2 having the projection 22 for the common electrode as apexes comprises a crystallized glass layer and the upper part thereof comprises a non-crystalline layer, the baking temp. of the glaze glass layer of the upper part can be set high and the surface roughness of the glaze glass layer can be reduced and this constitution is still more effective from an aspect of the elimination of separation in a film forming process.
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