Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material

Definitions

• This invention relates to the shaping of plastic compact discs (CD's) by injection molding for storing data in an optical medium.
• CD's plastic compact discs
• This invention relates to the provision of super-density compact discs where only one surface is required for the storage of information.
• Plastic discs having a pit optical track structure are well known as compact discs.
• Double sided discs in which information is recorded on two sides of such a structure formed by binding two compact discs and apparatus for playing such discs is also well known, as in U.S. patents 4,903,140; 4,939,011/ 5,097,465; 4,811,324.
• compact disc as used in thi ⁇ application includes any disc shaped recorded medium having pits and lands forming an optical track structure on a data information recording planar surface. Thus it includes such discs where the information stored as pits and lands is digital information or analog information.
• Digital information may be encoded into the pits and lands as pits of quantized lengths interpretable as a stream of digital data, wherein the length of each pit or land segment may be, for example, related to the number of l's or O's in a data stream.
• An example of such a system is the compact disc ("CD" ⁇ audio or video disc.
• Analog information may be encoded into the pits and lands as pit lengths that may vary over a continuum of values, wherein the length of each pit or land segment may be, for example, related to a voltage level in a desired output.
• An example of such a system is the laser disc video recording system.
• the present invention is a novel compact disc.
• Such discs are known to be plastic discs having pits and lands representing optically recorded data on an internal surface in which the internal surface carries a light reflective film and is overcoated by a transparent layer, that exposes a flat surface.
• two such discs are bonded to each other back to back. Where there is only the need for one surface to carry data the second disc is blank.
• the present invention provides a way to economize on the steps required for the manufacture of such discs .
• the d sc has two thickness regions.
• the first thickness region is a central cylindrical region.
• the second thickness region is the remaining annular region of the disc and has only a fraction of the thickness of said first region, said fraction being less than 3/4 and more than 1/4.
• the second annular region is overcoated with materials of different composition.
• Figure 1 depicts a prior art system employing a thin compact disc bonded to a blank compact disc to result in a disc that is usable in a double sided system even though all the data is present on only one side thereof.
• Figure 2 depicts a preferred embodiment of the present invention using a compact disc the plastic portion of which has substantial variations in thickness.
• the invention comprises a plastic disc having pits and lands representing optically recorded data on an internal surface thereof, the internal surface having a light reflective film thereon, and the surface being overcoated by a transparent layer exposing a flat surface.
• the disc has first and second thickness regions.
• the first thickness region is a central cylindrical region of a first predetermined thickness.
• the second thickness region comprises the remaining annular region of the disc and has a fraction of the thickness of said first region, the fraction being less than 3/4 and more than 1/4.
• the annular region is then overcoated with materials of different composition.

Landscapes

• Optical Recording Or Reproduction (AREA)
• Optical Record Carriers And Manufacture Thereof (AREA)
• Manufacturing Optical Record Carriers (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=24847563

Family Applications (1)

Country Status (3)

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Citations (4)

Family Cites Families (2)

• 1997
  • 1997-09-05 EP EP97941171A patent/EP0858657A4/de not_active Withdrawn
  • 1997-09-05 JP JP10512428A patent/JPH11515131A/ja active Pending
  • 1997-09-05 WO PCT/IB1997/001237 patent/WO1998010418A1/en not_active Application Discontinuation

Patent Citations (4)

Non-Patent Citations (3)

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