US4918683A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical information medium having a base plate made of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate
Assignee: Hitachi Ltd
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Filing: 1988-04-06
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Granted: 1990-04-17
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Expires: 2008-04-06
Abstract
Abstract An optical disc consists of a base plate, a reflective thin layer and a protective thin layer. As the base plate, polymethylmethacrylate is used. Since defects in the protective thin layer are a function of defects in the base plate, in order to reduce defects in the protective thin layer, defects in the base plate are reduced. For reducing defects in the base plate, a copolymer of methyl methacrylate and methyl acrylate is used.
Inventors
- 👤 Yoshie Kodera
- 👤 Hisashi Kabe
- 👤 Tetsu Ohishi
- 👤 Jun Matsumoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:01
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/24; G11B7/241; G11B7/252; G11B7/253; Y; Y10; Y10S; Y10S430/00; Y10S430/146
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
73 words
An optical information medium for reproducing recorded information optically, comprising a base plate and an information recorded layer supported on said base plate, wherein said base plate is made of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate, wherein a quantity of extracted monomer of said copolymer included in said base plate is less than 2 ppm after immersing in water at a temperature of 60° C. for seven days.
Claim 2
Dependent Claim
73 words
An optical information medium for reproducing recorded information optically, comprising a base plate and an information recorded layer supported on said base plate, wherein said base plate is made of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate, wherein a quantity of extracted monomer of said copolymer included in said base plate is less than 2 ppm after immersing in water at a temperature of 60° C. for seven days.
Claim 3
Dependent Claim
26 words
An optical information medium according to claim 1, wherein a melt flow index of said polymethylmethacrylate is within a range of 2 to 20 g/10 min.
Claim 4
Dependent Claim
19 words
An optical information medium according to claim 1, further comprising a protective layer provided over said information recorded layer.
Claim 5
Dependent Claim
17 words
An optical information medium according top claim 1, wherein said information recorded layer is a reflective layer.
Claim 6
Dependent Claim
40 words
An optical information medium according to claim 4, wherein said reflective layer is made of a material selected from the group consisting of the elements Al, Cu, Ag and Au or an alloy of at least one of aid elements.
Claim 7
Dependent Claim
26 words
An optical information medium according to claim 1, wherein said base plate consists essentially of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate.
Claim 8
Dependent Claim
17 words
An optical information medium according to claim 6, wherein said polymethylmethacrylate is formed by continuous bulk polymerization.
Claim 9
Dependent Claim
32 words
An optical information medium according to claim 1, wherein said base plate consists essentially of polymethylmethacrylate which is a copolymer of 88-95 wt. % methyl methacrylate and 5-12 wt. % methyl acrylate.
Claim 10
Dependent Claim
69 words
An optical information medium comprising a base plate and an information recordable layer supported on said base plate, wherein said base plate is made of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate and wherein a quantity of extracted monomer of said copolymer included in said base plate is less than 2 ppm after immersing in water at a temperature of 60° C. for seven days.
Claim 11
Dependent Claim
69 words
An optical information medium comprising a base plate and an information recordable layer supported on said base plate, wherein said base plate is made of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate and wherein a quantity of extracted monomer of said copolymer included in said base plate is less than 2 ppm after immersing in water at a temperature of 60° C. for seven days.
Claim 12
Dependent Claim
26 words
An optical information medium according to claim 9, wherein a felt flow index of said polymethylmethacrylate is within a range of 2 to 20 g/10 min.
Claim 13
Dependent Claim
19 words
An optical information medium according to claim 9, further comprising a protective layer provided over said information recorded layer.
Claim 14
Dependent Claim
26 words
An optical information medium according to claim 9, wherein said base plate consists essentially of polymethylmethacrylate which is a copolymer of methyl methacrylate and methyl acrylate.
Claim 15
Dependent Claim
17 words
An optical information medium according to claim 12, wherein said polymethylmethacrylate is formed by continuous bulk polymerization.
Claim 16
Dependent Claim
19 words
An optical information medium according to claim 9, wherein said information recordable layer is a write-once type memory layer.
Claim 17
Dependent Claim
18 words
An optical information medium according to claim 9, wherein said information recordable layer is an erasable-type memory layer.
Claim 18
Dependent Claim
32 words
An optical information medium according to claim 9, wherein said base plate consists essentially of polymethylmethacrylate which is a copolymer of 88-95 wt. % methyl methacrylate and 5-12 wt. % methyl acrylate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-04-16 | 1993-10-16 | 1994-04-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-04-16 | 1997-10-16 | 1998-04-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-04-16 | 2001-10-16 | 2002-04-17 | $7700.00 | Window Closed / Lapsed |