| 摘要 |
PURPOSE:To attain high rigidity by using an aluminum oxide sheet prepd. by baking a prepreg sheet obtained by casting the mixture of a sol of an aluminum oxide and aqueous polyvinyl alcohol solution as a surface member for at least one side of a core member. CONSTITUTION:The mixture between the sol of the aluminum oxide including 3wt% of polyvinyl alcohol and 1wt% of the aluminum oxide, and the polyvinyl alcohol aqueous solution is cast on a polyethylene sheet, and dried naturally to obtain the prepreg sheet having 50mum thickness. The sheet is baked at 1,500 deg.C to form the aluminum oxide sheet having 20mum thickness. This sheet is taken as the surface member 1 of the core member 2 made of aluminum alloy ribbon having 20mum thickness and used for at least one side of the core member 2. Thus, the diaphragm having light weight and the high rigidity is formed. |
