초록 ▼

A glass substrate for a magnetic disk of the present invention is one in which a laser beam is irradiated on a magnetic recording surface side thereby forming a large number of protrusions thereon to form texture thereon, each of the protrusions having a convex shape, an optical absorption coefficie

A glass substrate for a magnetic disk of the present invention is one in which a laser beam is irradiated on a magnetic recording surface side thereby forming a large number of protrusions thereon to form texture thereon, each of the protrusions having a convex shape, an optical absorption coefficient of a glass with respect to a wavelength of a laser beam at 266 nm being within a range of 20 to 2000 mm.sup.-1, the glass having a composition by weight of:

대표청구항 ▼

[ What is claimed is:] [1.] A glass substrate for a magnetic disk in which a laser beam is irradiated on a magnetic recording surface side thereby forming a large number of protrusions thereon to form texture thereon, each of said protrusions having a convex shape, an optical absorption coefficient

[ What is claimed is:] [1.] A glass substrate for a magnetic disk in which a laser beam is irradiated on a magnetic recording surface side thereby forming a large number of protrusions thereon to form texture thereon, each of said protrusions having a convex shape, an optical absorption coefficient of a glass with respect to a wavelength of a laser beam at 266 nm being within a range of 20 to 2000 mm.sup.-1, said glass having a composition by weight of:silicon oxide (SiO.sub.2): 58 to 66%,aluminum oxide (Al.sub.2 O.sub.3): 13 to 19%,lithium oxide (Li.sub.2 O): 3 to 4.5%,sodium oxide (Na.sub.2 O): 6 to 13%,potassium oxide (K.sub.2 O): 0 to 5%,R.sub.2 O: 9 to 18% (provided that R.sub.2 O=Li.sub.2 O+Na.sub.2 O+K.sub.2 O),magnesium oxide (MgO): 0 to 3.5%,calcium oxide (CaO): 1 to 7%;strontium oxide (SrO): 0 to 2%;barium oxide (BaO): 0 to 2%,RO: 2 to 10% (provided that RO=MgO+CaO+SrO+BaO),iron oxide (Fe.sub.2 O.sub.3): 0.05 to 2%,titanium oxide (TiO.sub.2): 0 to 2%,cerium oxide (CeO.sub.2): 0 to 2%, andmanganese oxide (MnO): 0 to 1%,(provided that Fe.sub.2 O.sub.3 +TiO.sub.2 +CeO.sub.2 +MnO=0.05 to 3%).