# US 10,766,806 B2 · Glass for data storage medium substrate, glass substrate for data storage medium, and magnetic disk

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- Number: US 10,766,806 B2
- Document ID: US10766806B2
- Status: Granted
- Kind: B2
- Application number: 15/945,144
- Filed: 2018-04-04
- Published: 2018-08-09
- Granted: 2020-09-08
- Earliest claimed: 2015-10-05
- Assignees: AGC Inc.
- Applicants: AGC Inc.
- Inventors: Eriko Maeda; Hiroyuki Hijiya; Kensuke Nagai; Tetsuya Nakashima; Yutaka Kuroiwa
- Web page: https://patentgrep.com/patent/US10766806B2

## CPC

- C03C 4/20: for chemical resistant glass
- C03C 3/085: containing an oxide of a divalent metal
- C03C 3/087: containing calcium oxide, e.g. common sheet or container glass
- C03C 3/091: containing aluminium
- C03C 21/00: Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
- G11B 5/73921: {Glass or ceramic substrates}
- C03C 2204/00: Glasses, glazes or enamels with special properties
- G11B 7/24047: Substrates
- H01F 41/14: for applying magnetic films to substrates
- 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
- 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)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES

## Abstract

The present invention pertains to a glass for a data storage medium substrate which contains a specific amount of each of SiO2, Al2O3, MgO, CaO, SrO, BaO, Li2O, Na2O, and K2O, in molar percentage based on the oxides, and does not substantially contain B2O3 or ZrO2, wherein the sum of the Li2O, Na2O, and K2O contents (R2O), the molar ratio of the SiO2 content to the Al2O3 content (SiO2/Al2O3), and the molar ratio of the sum of the SiO2 and Al2O3 contents (SiO2+Al2O3) to R2O[(SiO2+Al2O3)/R2O] fall within their specific ranges, formula (1): 90<[SiO2]+2×[Al2O3]+0.8×[RO]−0.5×[R2O] [in formula (1), RO represents the sum of the MgO, CaO, SrO, and BaO contents] is satisfied, and the glass transition point Tg, the alkali resistance, and the acid resistance fall within their specific ranges.

## Claims

### Claim 1

A glass comprising, in terms of mole percentage based on oxides:
60% or more of SiO2,
more than 8.5% and less than 13% of Al2O3,
0 to 5% of MgO,
1 to 12% of CaO,
0 to 2% of SrO,
0 to 2% of BaO,
0 to 1% of TiO2,
0% or more and less than 4% of Li2O,
3 to 12% of Na2O,
0% or more and less than 4% of K2O,
0% or more and less than 0.01% of B2O3, and
0% or more and less than 0.01% of ZrO2,
wherein:
a total content (R2O) of Li2O, Na2O and K2O is 3 to 12%,
a total content of SiO2 and Al2O3 is 80.5% or less,
a molar ratio (SiO2/Al2O3) of the SiO2 content to the Al2O3 content is higher than 5,
a molar ratio [(SiO2+Al2O3)/R2O] of a total content (SiO2+Al2O3) of SiO2 and Al2O3 to R2O is higher than 9, and
contents of SiO2, Al2O3, RO and R2O are such that a value obtained by the Formula (1) is greater than 90:
[SiO2]+2×[Al2O3]+0.8×[RO]−0.5×[R2O] Formula (1),
wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO.

### Claim 2 (depends on 1)

The glass according to claim 1, comprising 0.1 to 1% of TiO2.

### Claim 3 (depends on 1)

The glass according to claim 1, comprising 4 to 12% of CaO.

### Claim 4 (depends on 1)

The glass according to claim 1, comprising 7 to 12% of CaO.

### Claim 5 (depends on 1)

The glass according to claim 1, comprising 0 to 4% of MgO.

### Claim 6 (depends on 1)

The glass according to claim 1, comprising greater than 0% of ZrO2.

### Claim 7 (depends on 1)

The glass according to claim 1, wherein a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower.

### Claim 8 (depends on 1)

The glass according to claim 1, wherein the total content of SiO2 and Al2O3 is 79.0% or less.

### Claim 9

A glass comprising, in terms of mole percentage based on oxides:
60% or more of SiO2,
more than 6.5% and less than 13% of Al2O3,
0 to 5% of MgO,
1 to 12% of CaO,
0 to 2% of SrO,
0 to 2% of BaO,
0 to 1% of TiO2,
0% or more and less than 4% of Li2O,
3 to 12% of Na2O,
0% or more and less than 4% of K2O, and
0% or more and less than 0.01% of B2O3,
wherein:
a total content (R2O) of Li2O, Na2O and K2O is 3 to 12%,
a total content of SiO2 and Al2O3 is 80.5% or less,
a molar ratio (SiO2/Al2O3) of the SiO2 content to the Al2O3 content is higher than 5,
a molar ratio [(SiO2+Al2O3)/R2O] of a total content (SiO2+Al2O3) of SiO2 and Al2O3 to R2O is higher than 9, and
contents of SiO2, Al2O3, RO and R2O are such that a value obtained by the Formula (1) is greater than 90:
[SiO2]+2×[Al2O3]+0.8×[RO]−0.5×[R2O] Formula (1),
wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO.

### Claim 10 (depends on 9)

The glass according to claim 9, comprising 0.1 to 1% of TiO2.

### Claim 11 (depends on 9)

The glass according to claim 9, comprising 4 to 12% of CaO.

### Claim 12 (depends on 9)

The glass according to claim 9, comprising 7 to 12% of CaO.

### Claim 13 (depends on 9)

The glass according to claim 9, comprising 0 to 4% of MgO.

### Claim 14 (depends on 9)

The glass according to claim 9, further comprising 0% or more of ZrO2.

### Claim 15 (depends on 9)

The glass according to claim 9, wherein contents of MgO, Al2O3, CaO, Na2O and SiO2 are such that a value obtained by the Formula (2) is satisfied less than 30:
3×[MgO]+6×[Al2O3]−0.4×[CaO]+0.4×[Na2O]—[SiO2] Formula (2).

### Claim 16 (depends on 9)

The glass according to claim 9, wherein a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower.

### Claim 17 (depends on 9)

The glass according to claim 9, wherein the total content of SiO2 and Al2O3 is 79.0% or less.

### Claim 18 (depends on 9)

The glass according to claim 9, having a liquidus temperature TL lower than 1300° C.

### Claim 19 (depends on 9)

The glass according to claim 9, having a density less than 2.55 g/cm3.

### Claim 20 (depends on 9)

The glass according to claim 9, having a specific modulus of 31 MNm/kg or higher.

### Claim 21 (depends on 9)

The glass according to claim 9, having a temperature T2 at which a viscosity η reaches 102 poises (dPa·s) of lower than 1770° C.

### Claim 22 (depends on 9)

The glass according to claim 9, having a temperature T4 at which a viscosity η reaches 104 poises (dPa·s) of lower than 1280° C.

### Claim 23 (depends on 9)

The glass according to claim 9, having a thermal expansion coefficient of 10×10−7/° C. or higher.

### Claim 24 (depends on 9)

The glass according to claim 9, having a glass transition point Tg higher than 680° C.

### Claim 25 (depends on 9)

The glass according to claim 9, having an alkali resistance lower than 2 mg/cm2 and an acid resistance lower than 0.1 mg/cm2.

### Claim 26

A glass comprising, in terms of mole percentage based on oxides,
60% or more of SiO2,
4% or more and less than 15% of Al2O3,
0 to 5% of MgO,
1 to 12% of CaO,
0 to 7% of SrO,
0 to 5% of BaO,
0 to 10% of TiO2,
0% or more and less than 4% of Li2O
0% or more and less than 4% of K2O,
3% to 12% of Na2O,
0% or more and less than 0.01% of B2O3 and
0 to 5% of ZrO2,
wherein:
a total content of SiO2 and Al2O3 is 80.5% or less,
a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower, and
contents of SiO2, Al2O3, RO and R2O are such that a value obtained by the Formula (1) is 90 or more:
[SiO2]+2×[Al2O3]+0.8×[RO]−0.5×[R2O] Formula (1),
wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO, and R2O represents a total content of Li2O, Na2O and K2O.

### Claim 27 (depends on 26)

The glass according to claim 26, wherein, in terms of mole percentage based on oxides, MgO is less than 5% and at least any one of (1) to (3) is satisfied:
(1) greater than 0% and 4% or less of ZrO2 is contained;
(2) 7% or less of Na2O is contained; and
(3) 9% or less of Na2O, 11% or less of Al2O3 and 1% or more and 9.5% or less of CaO are contained.

### Claim 28 (depends on 26)

The glass according to claim 26, comprising 0 to 4% of MgO.

### Claim 29 (depends on 26)

The glass according to claim 26, wherein, in terms of mole percentage based on oxides, MgO is 5% and at least one of (4) and (5) is satisfied:
(4) greater than 0% and 4% or less of ZrO2 is contained; and
(5) 1% or more and 8.5% or less of CaO is contained.

### Claim 30 (depends on 26)

The glass according to claim 26, comprising 4% to 12% of CaO.

### Claim 31 (depends on 26)

The glass according to claim 26, comprising 7% to 12% of CaO.

### Claim 32 (depends on 26)

The glass according to claim 26, wherein the total content of SiO2 and Al2O3 is 79.0% or less.