| 摘要 |
PURPOSE:To make satisfactory the dynamic balance at the time of the use with a high accuracy by providing the steep rise part at the tip of plural conical protrusions provided at the inner and outer circumferential parts of one side substrate, unifying both substrates through the fused part and facilitating the assembling work. CONSTITUTION:At the inner circumferential part and the outer circumferential part of one side of substrates 31 and 35 having recording layers 41 and 45, plural protrusions 61 and 71 are provided. Bases 611 and 711 of the protrusion are conical, have fused parts 615 and 715 to rise steeply from the base at the tip, two substrates are faced and the ultrasonic wave fusion is executed, the fused part is effectively heated and unified. Consequently, the interval between substrates is determined at the base of the protrusion, the assembling accuracy is improved, the productivity is improved and the cost can be decreased. |
