| 摘要 |
Disclosed is a diaphragm having a flexible film portion and an outer peripheral flange portion integrally provided on the peripheral edge of the film portion, said outer peripheral flange portion being provided between and held by a first housing and a second housing, wherein the film portion is prevented from rising upward when the diaphragm is attached to the housings. The outer peripheral flange portion has a first pressed surface which is one surface of the diaphragm in the thickness direction and which is in close contact with the first housing, and a three-dimensional shape composed of a projected portion or a recessed portion, on the first pressed surface. When the outer peripheral flange portion is attached to the first housing and the second housing while being compressed and deformed therebetween, the three-dimensional shape defines voids in the thickness direction between the outer peripheral flange portion and the first housing.
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