(LA) NETHOD FORM MANAFACTURING ANNULAR GLASS PLATE, METHOD FOR MANAFACTURING GLASS SUBSTRATE FOR MAGNETIC DISK, METHOD FOR MANUFACTURING MAGNETIC DISK, ANNULAR GLASS PLATE, GLASS SUBSTE FOR MAGNETIC DISK, AND MANETIC DISK

(EN) NETHOD FORM MANAFACTURING ANNULAR GLASS PLATE, METHOD FOR MANAFACTURING GLASS SUBSTRATE FOR MAGNETIC DISK, METHOD FOR MANUFACTURING MAGNETIC DISK, ANNULAR GLASS PLATE, GLASS SUBSTE FOR MAGNETIC DISK, AND MANETIC DISK

(LA)

A method for manufacturing an annular glass plate that has an outer
circumferential edge surface, an inner circumferential edge surface, and a
thickness not larger than 0.6 mm includes processing for manufacturing an 
annular glass plate by irradiating each of the outer circumferential edge surface
and the inner circumferential edge surface of an annular glass blank with a laser
beam to melt the outer circumferential edge surface and the inner
circumferential edge surface and form molten surfaces such that the molten
surfaces in the outer circumferential edge surface and the inner circumferential 
edge surface each have an arithmetic average surface roughness Ra not larger
than 0.1 μm, and the surface roughness of the molten surface in the inner
circumferential edge surface becomes larger than the surface roughness of the
molten surface in the outer circumferential edge surface.