# US 2001/0022705 A1 · Glass substrate for recording medium

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- Number: US 2001/0022705 A1
- Document ID: US20010022705A1
- Status: Published application
- Kind: A1
- Application number: 09/808,020
- Filed: 2001-03-15
- Published: 2001-09-20
- Earliest claimed: 2000-03-16
- Inventors: Toshiharu Mori; Hideki Kawai; Akira Sugimoto; Hiroshi Yuki; Hideki Nagata; Kazuhiko Ishimaru
- Web page: https://patentgrep.com/patent/US20010022705A1

## CPC

- G11B 7/24: Record carriers characterised by shape, structure or physical properties, or by the selection of the material (characterised by the arrangement of information on the carrier G11B7/007)
- C03B 32/02: Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles {(C03B27/012 takes precedence)}
- C03C 3/085: containing an oxide of a divalent metal
- C03C 15/00: Surface treatment of glass, not in the form of fibres or filaments, by etching (etching or surface-brightening compositions, in general C09K13/00)
- G11B 5/73921: {Glass or ceramic substrates}
- G11B 5/8404: {manufacturing base layers}
- G11B 7/2531: comprising glass
- G11B 23/0021: {discs}
- G11B 7/2532: comprising metals
- G11B 7/26: Apparatus or processes specially adapted for the manufacture of record carriers
- G11B 11/10582: {Record carriers characterised by the selection of the material or by the structure or form}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS

## Abstract

A polished glass disk medium substrate table for use as a substrate for a hard disk, a hard disk containing the substrate and methods for making the substrate. Glass forming raw materials are formed into a disk having a diameter between about 70 mm and about mm, a thickness between about 0.7 mm and about 0.9 mm, a flutter of less than 90 nm at 10,000 rpm.

## Claims

### Claim 1

A polished glass disk medium substrate suitable for use as a substrate for a disk medium said disk having a diameter between about 70 mm and about 90 mm, a thickness between about 0.7 mm and about 0.9 mm, and a flutter of less than about 90 nm at 10,000 rpm.

### Claim 2 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said polished glass disk comprises crystallized glass.

### Claim 3 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said flutter is less than 58 nm at 10,000 rpm.

### Claim 4 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said glass has a Log η of 1.5 or higher at 1400° C. when the viscosity of the glass is η poise.

### Claim 5 (depends on 4)

The polished glass disk medium substrate according to claim 4, wherein said glass has a Log η of 2.5 or higher at 1400° C. when the viscosity of the glass is η poise.

### Claim 6 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said glass has a Log η of 2.0 or higher at 1300° C. when the viscosity of the substrate is η poise.

### Claim 7 (depends on 6)

The polished glass disk medium substrate according to claim 6, wherein said glass has a Log η of 3.0 or higher at 1300° C. when the viscosity of the substrate is η poise.

### Claim 8 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said glass has a Log η of 2.4 or higher at 1300° C. when the viscosity of the substrate is η poise.

### Claim 9 (depends on 8)

The polished glass disk medium substrate according to claim 8, wherein said glass has a Log η of 3.5 or higher at 1200° C. when the viscosity of the substrate is η poise.

### Claim 10 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein the glass disk medium has an internal friction coefficient of between about 8×10−4 and about 16×10−4.

### Claim 11 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein the proportion of dynamic energy loss due to natural vibration per one-cycle added to the suspended disk media glass is between about 8×10−4 and about 16×104.

### Claim 12 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein the glass disk medium possesses a damping coefficient of between about 5×10−4 and about 12×10−4.

### Claim 13 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein the glass disk medium possesses a loss coefficient due to attenuation of natural vibration generated by impact of between about 5×10−4 and 12×10−4.

### Claim 14 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein the glass has a specific gravity of less than about 3.

### Claim 15 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said glass comprises:
ab out 45% to about 60% by weight SiO2;
about 12% to about 20% by weight Al2O3;
about 0.1% to about 4% by weight Li2O;
about 12% to about 20% by weight MgO;
about 2% to about 60% by weight TiO2;
optionally about 0.1% to about 5% by weight Disk2O;
optionally about 0.1% to about 5% by weight P2O5; and
optionally about 0.1% to about 5% by weight Sb2O3.

### Claim 16 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said glass is essentially free of BaO, ZnO, ZrO2, B2O3 NiO, and Y.

### Claim 17 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said K2O is not optional.

### Claim 18 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said P2O5 is not optional.

### Claim 19 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said Sb2O3 is not optional.

### Claim 20 (depends on 1)

The polished glass disk medium substrate according to claim 1, wherein said substrate is prepared by heating glass forming raw materials to a temperature, T1, between about 730 and 770° C.; maintaining the temperature T1 for a time between about 2 and about 7 hours; heating the glass forming raw materials to a temperature, T2, between about 820 and 900° C.; and maintaining the temperature T2 for a time between about 3 and about 9 hours.

### Claim 21 (depends on 1)

A disk medium comprising the polished glass disk medium substrate defined in claim 1.

### Claim 22 (depends on 21)

The disk medium according to claim 21, wherein said disk medium is a high density recording disk.

### Claim 23 (depends on 21)

The disk medium according to claim 21, wherein said disk medium is a magnetic recording medium.

### Claim 24 (depends on 21)

The disk medium according to claim 21, wherein said disk medium is an optical recording medium.

### Claim 25 (depends on 21)

The disk medium according to claim 21, wherein said disk medium is a magnetic-optical recording medium.

### Claim 26

A method of making a glass disk medium substrate comprising:
heating glass forming raw materials to a temperature sufficiently high to melt the raw materials;
forming a disk medium substrate; and crystallizing the disk medium substrate, wherein said crystallizing comprises heating the disk medium substrate to a temperature, T1, between about 730 and 770° C.; maintaining the temperature T1 for a time between about 2 and about 7 hours; heating the glass forming raw materials to a temperature, T2, between about 820 and 900° C.; and maintaining the temperature T2 for a time between about 3 and about 9 hours.

### Claim 27 (depends on 26)

The method according to claim 26, wherein said forming comprises fluid dripping the melted raw materials onto a mold and applying pressure to form a desired shape.

### Claim 28 (depends on 26)

The method according to claim 26, wherein said crystallizing occurs in a thermo-regulated bath.

### Claim 29 (depends on 26)

The method according to claim 26, further comprising forming a hole in the center of said glass disk medium substrate.

### Claim 30 (depends on 26)

The method according to claim 26, further comprising subjecting the glass disk medium substrate to an abrasion process.

### Claim 31 (depends on 30)

The method according to claim 30, wherein said abrasion process comprises grinding.

### Claim 32 (depends on 30)

The method according to claim 30, further comprising polishing said glass disk medium substrate.

### Claim 33 (depends on 26)

The method according to claim 26, further comprising annealing said glass disk medium substrate after said heating at temperature T2.

### Claim 34 (depends on 22)

The method according to claim 22, wherein said glass disk medium substrate formed has a diameter between about 70 mm and about 90 mm, a thickness between about 0.7 mm and about 0.9 mm, and a flutter of less than about 90 nm at 10,000 rpm.