US4397805A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for making a video disc
Assignee: Discovision Associates
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Filing: 1981-11-03
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Granted: 1983-08-09
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Expires: 2001-11-03
Abstract
Abstract A video disc member is described having a uniform value of birefringence over the entire information storage surface of the disc. This value of birefringence is the same at the inner information storage radius as at the outer information storage radius. The preferable composition of the video disc is a specially prepared polymethylmethacrylate, referred to as PMMA. The method of molding the improved video disc member includes an extended drying time for said composition and increasing the melting temperature. The increase in melt temperature provides a low and uniform value of birefringence. The improved drying cycle eliminates splay marks, blisters and other surface imperfections as compared to manufacturer recommended drying times.
Inventors
- 👤 John R. Holmes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:30
CPC Classifications
G; G11; G11B; G11B3/00; G11B3/68; G11B3/70; G11B3/705; G11B3/707; B; B41; B41C; B41C3/00; B41C3/06; G11B7/00; G11B7/24; G11B7/26; Y; Y10; Y10S; Y10S425/00; Y10S425/81
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
60 words
A method for forming an optically readable information bearing structure, comprising the steps of: processing a clear polymethylmethacrylate plastic to a melt flow rate of about 20 to about 23 grams per 10 minutes; heating the plastic to a temperature falling within the range of 510° F. to 560° F.; and using said heated plastic in an injection molding cycle.
Claim 2
Independent Claim
60 words
A method for forming an optically readable information bearing structure, comprising the steps of: processing a clear polymethylmethacrylate plastic to a melt flow rate of about 20 to about 23 grams per 10 minutes; heating the plastic to a temperature falling within the range of 510° F. to 560° F.; and using said heated plastic in an injection molding cycle.
Claim 3
Dependent Claim
15 words
A method as recited in claim 1 wherein the plastic contains substantially no foreign particles.
Claim 4
Dependent Claim
25 words
A method as recited in claim 1 wherein the plastic contains foreign particles with a size range between about 1 micron and about 10 microns.
Claim 5
Dependent Claim
32 words
A method as recited in claim 1 wherein the plastic contains from about 0.5% to about 0.8% by weight lubricant, and wherein the lubricant has a vaporization temperature above the heating temperature.
Claim 6
Dependent Claim
22 words
A method as recited in claim 1 and further comprising the step of: thoroughly drying said plastic prior to said heating step.
Claim 7
Dependent Claim
20 words
A method as recited in claim 5 wherein the plastic is dried for about 24 hours to about 48 hours.
Claim 8
Dependent Claim
72 words
A process for making an optically readable information bearing member of substantially low and uniform birefringence, comprising the steps of: (i) processing a clear polymethylmethacrylate plastic to a melt flow rate of about 20 to about 23 grams per 10 minutes; (ii) thoroughly drying the plastic; (iii) putting the dried plastic into an injection molding machine wherein the temperature of the melt is maintained between about 510° F. and about 560° F.
Claim 9
Dependent Claim
72 words
A process for making an optically readable information bearing member of substantially low and uniform birefringence, comprising the steps of: (i) processing a clear polymethylmethacrylate plastic to a melt flow rate of about 20 to about 23 grams per 10 minutes; (ii) thoroughly drying the plastic; (iii) putting the dried plastic into an injection molding machine wherein the temperature of the melt is maintained between about 510° F. and about 560° F.
Claim 10
Dependent Claim
20 words
A process is recited in claim 7 wherein the plastic is dried for about 24 hours to about 48 hours.
Claim 11
Dependent Claim
27 words
A process as recited in claim 7 wherein the temperature of the melt is maintained at about 560° F. and the molding time is about 0.5 second.
Claim 12
Dependent Claim
15 words
A process as recited in claim 7 wherein the plastic contains substantially no foreign particles.
Claim 13
Dependent Claim
25 words
A process as recited in claim 7 wherein the plastic contains foreign particles with a size range between about 1 micron and about 10 microns.
Claim 14
Dependent Claim
32 words
A process as recited in claim 7 wherein the plastic contains from about 0.5% to about 0.8% by weight lubricant, and wherein the lubricant has a vaporization temperature above the heating temperature.
Claim 15
Dependent Claim
14 words
A process as recited in claim 7 wherein the plastic contains substantially no monomers.
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) | 1986-08-08 | 1987-02-07 | 1987-08-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-08-08 | 1991-02-07 | 1991-08-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-08-08 | 1995-02-07 | 1995-08-09 | $7700.00 | Window Closed / Lapsed |