Stock material or miscellaneous articles – Circular sheet or circular blank
Patent
1997-01-07
2000-09-19
Evans, Elizabeth
Stock material or miscellaneous articles
Circular sheet or circular blank
428 642, 428 644, 4284255, 428913, 43027011, 4304951, 430945, 369283, 369288, 2504921, 427596, B32B 300
Patent
active
061208701
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an optical disk and the method for producing the optical disk.
BACKGROUND OF THE INVENTION
Conventional production methods for optical disks include, for example, a method in which first an original metal plate (stamper) is created with a negative image of the pattern to be formed on a plastic substrate that forms an optical disk. Then, a substrate is produced by injection molding from the stamper. The stamper is produced, for example, by the method illustrated in FIGS. 11A-E. This particular method is described below.
Generally, an original glass plate is used to create a stamper, and a photoresist 112 is applied to the glass plate 111 as shown in FIG. 11A. Then, as shown in FIG. 11B, a pattern based on the desired information is exposed onto the photoresist 112 using a laser cutting machine. Next, the photoresist 112 is developed, and exposed areas are removed to form a relief-and-indentation pattern on the surface, as shown in FIG. 11C. Then, as shown in FIG. 11D, conductivity treatment is applied (a metal film is vacuum-formed) to the photoresist 112 where the pattern is formed, and nickel plating 113 is added. Next, a nickel stamper 114 is created by separating the nickel plating 113 from the original glass plate 111 on which the pattern was formed, as shown in FIG. 11E.
Injection molding is a method that uses the stamper to produce plastic substrates. Generally, a polycarbonate is used as the plastic substrate material.
Japanese laid-open patent publications No. 1-150529 and No. 4229430 respectively disclose an optical disk in which a cyclic olefin copolymer is used. These publications disclose that the use of a substrate for an optical disk made of a given ethylene/cyclic olefin polymer and a set item of given composition for its adhesive layer allows the production of an optical recording medium that has an adhesive layer with excellent in adhesive strength, water-proofness and moisture-resistance, as well as a substrate layer with superior dimensional stability even under high-temperature and high-humidity conditions, as well as under normal conditions. Further, this substrate has the advantages of excellent heat-resistance and transparency, and it has no color and only a small birefringence, and it hardly warps.
A production method for optical disks using UV-curing resin is disclosed in Japanese laid-open patent publication No. 53-86756. This publication discloses a method that uses UV-curing resin to transfer a pattern to a polymethyl methacrylate, a polycarbonate, etc. a master made of nickel by electroforming (hereinafter, a "master" is used as the equivalent of a stamper).
Alternatively, a method that uses a silicon wafer to create a master for optical disks is disclosed in Japanese laid-open patent publication No. 61-68746. According to the method as disclosed in this publication, silicon oxide is formed on a silicon wafer after which a photoresist is applied and exposed. The photoresist is developed and then the silicon oxide is etched to create a master.
Also, replicas for molding can be produced by other methods from a master made of silicon. Japanese laid-open patent publication No. 4-299937 discloses a method for creating a master by directly etching a silicon wafer. Also, Japanese laid-open patent publication No. 5-62254 discloses a method that uses UV-curing resin to transfer a pattern from a master made of a silicon wafer to a plastic substrate.
Methods disclosed in Japanese laid-open patent publications No. 4-310624 and No. 4-311833 have the advantage that a master produced using a silicon wafer yields optical disks that have enhanced recording density.
Still, it is necessary to highly densify a recording pattern formed on an optical disk in order to increase the amount of data recorded on the disk. To achieve high densification by conventional methods, it is necessary to increase the density of the pattern formed on the stamper. For this reason, it is common to employ a method that reduces the laser wavelength of a laser c
REFERENCES:
patent: 4275091 (1981-06-01), Lippits et al.
patent: 4874808 (1989-10-01), Minami et al.
patent: 5439722 (1995-08-01), Brekner
Nebashi Satoshi
Nishikawa Takao
Takakuwa Atsushi
Evans Elizabeth
Seiko Epson Corporation
Watson Mark P.
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