Abstract: A method for producing a glass substrate for a magnetic disk involving the use of a polishing pad having: a first resin foam layer which forms the polishing surface, includes a resin foam having pores with a pore diameter of more than 20 ?m and has a thickness of 400 ?m or less; and a second resin foam layer which is provided between a platen for fixing the polishing pad and the first resin foam layer, includes a resin foam having pores with a pore diameter of 20 ?m or less and has a thickness of 50 to 250 ?m, and in which a total thickness of the first resin foam layer and the second resin foam layer is 550 ?m or less, and a international rubber hardness degree of the polishing pad measured by the M method according to JIS K6253 is 40 IRHD or more.

Abstract: The present invention relates to a method for producing a glass substrate for a magnetic disk, the method including a step of polishing a main surface of a circular glass plate while supplying a polishing slurry containing a polishing material, in which polishing is performed, after a polishing surface is subjected to dressing treatment, by using a polishing pad having: a first resin foam layer which forms the polishing surface, includes a resin foam having pores with a pore diameter of more than 20 ?m and has a thickness of 400 ?m or less; and a second resin foam layer which is provided between a platen for fixing the polishing pad and the first resin foam layer, includes a resin foam having pores with a pore diameter of 20 ?m or less and has a thickness of 50 to 250 ?m, and in which a total thickness of the first resin foam layer and the second resin foam layer is 550 ?m or less, and a international rubber hardness degree of the polishing pad measured by the M method according to JIS K6253 is 40 IRHD or mor

Abstract: The present invention relates to a glass substrate for a magnetic recording medium, which is a disk-shaped glass substrate for a magnetic recording medium having a circular hole at the center thereof, in which the glass substrate for a magnetic recording medium has an inner peripheral side surface, an outer peripheral side surface and both main surfaces, and the both main surfaces have parallelism of 3.2 ?m or less in at least a recording and reproducing region thereof.

Abstract: Dressing treatment of a polishing pad, adjusting a polishing surface of the polishing pad to given flatness and surface roughness without deteriorating productivity, a method for polishing a glass substrate, including polishing a main surface of a glass substrate using the polishing pad adjusted by the dressing treatment, and a method for manufacturing a glass substrate using the polishing method are provided. A dressing jig having arithmetic surface roughness on a surface performing dressing treatment of from 0.10 ?m to 2.5 ?m is used as the dressing jig for adjusting a polishing surface of the polishing pad to given flatness and surface roughness. A main surface of the glass substrate is polished with the polishing surface of the polishing pad having been subjected to a dressing treatment using the dressing jig.

Abstract: The present invention relates to a method for producing a glass substrate for a magnetic disk, the method including a step of polishing a main surface of a circular glass plate while supplying a polishing slurry containing a polishing material, in which polishing is performed, after a polishing surface is subjected to dressing treatment, by using a polishing pad having: a first resin foam layer which forms the polishing surface, includes a resin foam having pores with a pore diameter of more than 20 ?m and has a thickness of 400 ?m or less; and a second resin foam layer which is provided between a platen for fixing the polishing pad and the first resin foam layer, includes a resin foam having pores with a pore diameter of 20 ?m or less and has a thickness of 50 to 250 ?m, and in which a total thickness of the first resin foam layer and the second resin foam layer is 550 ?m or less, and a international rubber hardness degree of the polishing pad measured by the M method according to JIS K6253 is 40 IRHD or mor

Abstract: A method for cleaning a disk-shape glass substrate, which comprises rotating the disk-shape glass substrate on its center with its main surface vertical, and making a cleaning fluid irradiated with ultrasonic waves run down on the outer peripheral edge surface of the rotating glass substrate.

Abstract: A method for producing a glass substrate for magnetic disk, which is capable of effectively removing a crack is provided. In the method for producing a glass substrate for magnetic disk, there were provided a preparation step 1 of preparing a circular glass substrate having a main surface, a back surface opposing to the main surface, an inner side surface defining a through-hole penetrating from the main surface to the back surface and an outer side surface opposing to the inner side surface; a pre-polishing step 2A of polishing the inner side surface and the outer side surface of the glass substrate; a lapping step 3 of lapping the polished glass substrate; and a post-polishing step 2B of polishing the inner side surface and the outer side surface of the lapped glass substrate.

Abstract: A process for producing a glass substrate for a magnetic disk, which comprises etching an edge surface of circular glass, followed by polishing.

Abstract: A method for cleaning a disk-shape glass substrate, which comprises rotating the disk-shape glass substrate on its center with its main surface vertical, and making a cleaning fluid irradiated with ultrasonic waves run down on the outer peripheral edge surface of the rotating glass substrate.

Abstract: A glass substrate for magnetic disks, which is a doughnut-type glass substrate with its inner peripheral edge surface etching-treated, wherein the etching-treated inner peripheral edge surface is coated with a silicone resin or a polyimide.

Abstract: A glass substrate for magnetic disks, obtained by chemical strengthening treatment of a glass consisting essentially of from 50 to 65 wt % of SiO.sub.2, from 5 to 15 wt % of Al.sub.2 O.sub.3, from 2 to 7 wt % of Na.sub.2 O, from 4 to 9 wt % of K.sub.2 O, from 7 to 14 wt % of Na.sub.2 O+K.sub.2 O, from 12 to 25 wt % of MgO+CaO+SrO+BaO, and from 1 to 6 wt % of ZrO.sub.2.

Abstract: To reduce occurrence of flaws in a polishing process by preventing an abrasive grain or metallic particles deposited on the surface of a glass substrate for a magnetic disk in a lapping process from entering into the subsequent polishing process. A lapping process for the main surface is a glass substrate for a magnetic disk is conducted; an etching process for the main surface of the glass substrate is conducted to the extent of a depth of 0.1 .mu.m to 3 .mu.m, followed by conducting a polishing process for the main surface of the glass substrate where the etching process has been conducted.

Abstract: A glass disk is subjected to a chemical or gentle mechanical polishing step to remove microcracks or scratches in the disk surface prior to chemically texturing the disk. Thereafter, magnetic media is deposited onto the glass disk. We have discovered that by performing this pre-texturing polishing step, we can avoid the phenomenon of "linkage bumps," which could otherwise cause the resulting magnetic disk to fail a glide-type test or to cause a read/write head crash.