Optical disk for use in optical memory devices

• US 5,399,461 A
• Filed: 03/17/1993
• Issued: 03/21/1995
• Est. Priority Date: 08/21/1987
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ohta, Kenji, Inui, Tetsuya, Takemori, Hirotoshi, Nagaura, Toshikazu, Van, Kazuo, Toki, Hirotaka
• Primary Examiner(s): Bowers, Jr., Charles L.
• Assistant Examiner(s): Angebranndt, Martin J.
• Application Number:
  US08/032,540
• Time in Patent Office: 734 Days
• Field of Search: 430/320, 430/321, 430/322, 430/495, 430/945, 369/275.1, 369/275.3, 369/275.4, 369/288
• US Class Current: 430/321
• CPC Class Codes: G11B 7/24085 Pits
• CPC Class Codes: G11B 7/261 Preparing a master, e.g. exposing photoresist, electroforming
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

An optical disk for use in an optical memory device having guide grooves and pits on one surface thereof, wherein the depth of the guide grooves is different from that of the pits and the distance from the bottom face of each of the guide grooves to the other surface of the optical disk opposite to the one surface of the optical disk on which the guide grooves and pits are disposed is the same as the distance from the bottom face of each of the pits to the other surface of the optical disk opposite to the one surface of the optical disk on which the guide grooves and pits are disposed, and a method for the production of optical memory master plates that are used for the production of the above-mentioned optical disk.

Claims

1. A method for the production of an optical memory master plate for creating an optical disk having a plurality of substantially parallel and radially extending guide tracks and information pits formed therebetween, using a disk plate having a first surface and a second surface, the steps comprising:

forming a photoresist film on the first surface of said disk plate;

exposing said photoresist film to first and second columns of laser beams;

developing said photoresist film resulting in a patterned photoresist film;

forming a metal film on the first surface of said disk plate with the patterned photoresist film, and

wherein said exposing step further comprising,

disposing said first and second columns of laser beams in a radial direction along the first surface of said disk plate illuminating said photoresist film through an object lens by radially shifting said laser beams in such a way that a portion of one of said laser beams is superimposed upon an adjacent previously exposed area resulting in an exposed area that is wider than the previously exposed area formed before said laser beams are shifted, said widely exposed area defining a plurality of guide groove latent images along a fixed radial path, and

shifting a selected one of said first and second columns of laser beams on said fixed radial path and deflecting said other column away from said disk plate thereby illuminating said photoresist film in defined areas using said selected column for forming information pits between said widened guide grooves and along said fixed path, so that a disk plate is formed with a first surface and a second surface, with grooves and pits of different depths with the bottom of the pits and grooves being equidistant spaced from said second surface,

wherein said exposing step further comprises;

adjusting the relative position between said first and second beams said fixed distance for forming a land area between said plurality of guide grooves so that said first surface has a first top portion containing said pits and a second top portion containing said grooves, and said first top portion is spaced a greater distance from said second surface than said second top portion.

2. The method for producing an optical memory master plate as recited in claim 1, wherein said exposing step further comprises:

adjusting the intensity of said first and second columns of laser beams for forming said guide grooves and said selected laser beam column for forming said information pits so that the bottom surfaces of said guide grooves have a different depth when measured from a surface of said second top portion than the depths of said information pits when measured from the first surface of said photoresist film and said bottom surfaces of both said guide grooves and said information pits being of equal distance from the second surface of said disk plate.

3. A method according to claim 1, wherein said disk plate is made from the group consisting of glass or plastic.

4. A method for the production of an optical memory master plate for creating an optical disk having a plurality of substantially parallel and radially extending guide tracks and information pits formed therebetween, using a disk plate having a first surface and a second surface, the steps comprising:

forming only a single photoresist film on the first surface of said disk plate;

exposing said single photoresist film to first and second columns of laser beams;

developing said single photoresist film resulting in a patterned photoresist film;

forming a metal film on the first surface of said disk plate with the patterned single photoresist film, and

wherein said exposing step further comprising,

disposing said first and second columns of laser beams in a radial direction along the first surface of said disk plate illuminating said photoresist film through an object lens by radially shifting said laser beams in such a way that a portion of one of said laser beams is superimposed upon an adjacent previously exposed area resulting in an exposed area that is wider than the previously exposed area formed before said laser beams are shifted, said widely exposed area defining a plurality of guide groove latent images along a fixed radial path, and

shifting a selected one of said first and second columns of laser beams on said fixed radial path and deflecting said other column away from said disk plate thereby illuminating said photoresist film in defined areas using said selected column for forming information pits between said widened guide grooves and along said fixed path, so that a disk plate is formed with a first surface and a second surface, with grooves and pits of different depths with the bottom of the pits and grooves being equidistant spaced from said second surface,

wherein said exposing step further comprises;

adjusting the relative position between said first and second beams said fixed distance for forming a land area between said plurality of guide grooves so that said first surface has a first top portion containing said pits and a second top portion containing said grooves, and said first top portion is spaced a greater distance from said second surface than said second top portion.