US4849304A
Expired / Lapsed
US
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Optical recording medium
Assignee: TDK Corp
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Filing: 1987-12-16
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Granted: 1989-07-18
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Expires: 2007-12-16
Abstract
Abstract An optical recording medium comprising a recording layer on a substrate and a protective layer formed adjacent to the upper and/or lower surface of the recording layer is more durable and corrosion resistant when the protective layer has a composition comprising, in % by weight, 40-60% of SiO 2 , 0.5-10% of an alkali metal oxide, 10-59.5% of Al 2 O 3 and/or B 2 O 3 , and optionally up to 50% of a divalent metal oxide.
Inventors
- 👤 Kenji Uchiyama
- 👤 Hideki Ishizaki
- 👤 Hajime Utsunomiya
- 👤 Suguru Takayama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 12:24
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; G11B7/00; G11B7/24; G11B7/241; G11B7/252; G11B7/257; G11B7/2578; G11B7/242; G11B7/243; G11B2007/24302; G11B2007/24306; G11B2007/25705; G11B2007/25708; G11B2007/2571; G11B2007/25715; G11B7/253; G11B7/2533; G11B7/2534; G11B7/254; G11B7/2542; G11B7/256; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
112 words
A magneto optical recording medium comprising a substrate, a recording layer formed on the substrate, said recording layer having upper and lower surfaces disposed remote from and adjacent to the substrate, respectively, and at least one protective layer formed adjacent to the upper or lower surface of said recording layer, said protective layer having a composition comprising, in % by weight based on the total weight of the composition, (a) about 40 to 60% of silicon oxide calculated as SiO 2 , (b) about 0.5 to 10% of an alkali metal oxide, and (c) about 30 to 59.5% of aluminum oxide, boron oxide, or a mixture of aluminum oxide and boron oxide.
Claim 2
Dependent Claim
112 words
A magneto optical recording medium comprising a substrate, a recording layer formed on the substrate, said recording layer having upper and lower surfaces disposed remote from and adjacent to the substrate, respectively, and at least one protective layer formed adjacent to the upper or lower surface of said recording layer, said protective layer having a composition comprising, in % by weight based on the total weight of the composition, (a) about 40 to 60% of silicon oxide calculated as SiO 2 , (b) about 0.5 to 10% of an alkali metal oxide, and (c) about 30 to 59.5% of aluminum oxide, boron oxide, or a mixture of aluminum oxide and boron oxide.
Claim 3
Dependent Claim
48 words
The magneto optical recording medium of claim 1 wherein the protective layer composition further comprises (d) up to about 29.5% of a metal oxide represented by M(II)O wherein M(II) is a divalent metal, provided that the total of components (c) and (d) ranges from about 30 to 59.5%.
Claim 4
Dependent Claim
23 words
The magneto optical recording medium of claim 2 wherein the content of metal oxide represented by M(II)O ranges from about 10 to 49.5%.
Claim 5
Dependent Claim
21 words
The magneto optical recording medium of claim 1 wherein the content of alkali metal oxide ranges from about 1.0 to 7.0%.
Claim 6
Dependent Claim
32 words
The magneto optical recording medium of claim 1 wherein component (c) is a mixture of aluminum oxide and boron oxide with the content of boron oxide ranging from about 1 to 40%.
Claim 7
Dependent Claim
32 words
The magneto optical recording medium of claim 1 wherein component (c) is a mixture of aluminum oxide and boron oxide with the content of aluminum oxide ranging from about 3 to 45%.
Claim 8
Dependent Claim
33 words
The magneto optical recording medium of claim 1 wherein the protective layer composition further comprises at least one rare earth element selected from the group consisting of yttrium, lanthanide elements and actinide elements.
Claim 9
Dependent Claim
19 words
The magneto optical recording medium of claim 1 wherein the recording layer is comprised of a magnetic thin film.
Claim 10
Dependent Claim
41 words
The magneto optical recording medium of claim 1 which further comprises an intermediate layer formed contiguous to the lower surface of said recording layer from at least one member selected from the group consisting of an oxide, carbide, nitride, and sulfide.
Claim 11
Dependent Claim
48 words
The magneto optical recording medium of claim 9 wherein the intermediate layer contains at least one member selected from each of the groups consisting of metal compounds and metalloid compounds, wherein said members selected from metals and metalloids compounds are present in the form of oxides or nitrides.
Claim 12
Dependent Claim
121 words
The magneto optical recording medium of claim 1 wherein one protective layer is formed adjacent to the upper surface of said recording layer and another protective layer is formed adjacent to the lower surface of said recording layer, wherein at least one of said protective layer formed adjacent to the upper surface and said protective layer formed adjacent to the lower surface has said composition comprising, in % by weight based on the total weight of the composition, (a) about 40 to 60% of silicon oxide calculated as SiO 2 , (b) about 0.5 to 10% of an alkali metal oxide, and (c) about 30 to 59.5% of aluminum oxide, boron oxide, or a mixture of aluminum oxide and boron oxide.
Claim 13
Dependent Claim
131 words
A magneto optical recording medium comprising a substrate, a recording layer formed on the substrate, said recording layer having upper and lower surfaces disposed remote from and adjacent to the substrate, respectively, and at least one protective layer formed adjacent to the upper or lower surface of said recording layer, said protective layer having a composition comprising, in % by weight based on the total weight of the composition, (a) about 40 to 60% of silicon oxide calculated as SiO 2 , (b) about 0.5 to 10% of an alkali metal oxide, and (c) about 10 to 49.5% of aluminum oxide, boron oxide, or a mixture of aluminum oxide and boron oxide, and (d) about 10 to 49.5% of a metal oxide represented by M(II)O wherein M(II) is a divalent metal.
Claim 14
Dependent Claim
131 words
A magneto optical recording medium comprising a substrate, a recording layer formed on the substrate, said recording layer having upper and lower surfaces disposed remote from and adjacent to the substrate, respectively, and at least one protective layer formed adjacent to the upper or lower surface of said recording layer, said protective layer having a composition comprising, in % by weight based on the total weight of the composition, (a) about 40 to 60% of silicon oxide calculated as SiO 2 , (b) about 0.5 to 10% of an alkali metal oxide, and (c) about 10 to 49.5% of aluminum oxide, boron oxide, or a mixture of aluminum oxide and boron oxide, and (d) about 10 to 49.5% of a metal oxide represented by M(II)O wherein M(II) is a divalent metal.
Claim 15
Dependent Claim
33 words
The magneto optical recording medium of claim 12 wherein the protective layer composition further comprises at least one rare earth element selected from the group consisting of yttrium, lanthanide elements and actinide elements.
Claim 16
Dependent Claim
37 words
The magneto optical recording medium of claim 13 wherein the rare earth element is present in an amount of about 3 to 175 atom % based on the total of silicon, alkali metal, and aluminum and/or boron.
Claim 17
Dependent Claim
37 words
The magneto optical recording medium of claim 7 wherein the rare earth element is present in an amount of about 3 to 175 atom % based on the total of silicon, alkali metal, and aluminum and/or boron.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-17 | 1993-01-16 | 1993-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-17 | 1997-01-16 | 1997-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-17 | 2001-01-16 | 2001-07-18 | $7700.00 | Window Closed / Lapsed |