Method for fabrication of disc substrate

• US 5,552,098 A
• Filed: 03/03/1994
• Issued: 09/03/1996
• Est. Priority Date: 10/12/1991
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kudo, Junichiro, Shimizu, Jun
• Primary Examiner(s): Woo, Jay H.
• Assistant Examiner(s): SMITH, DUANE
• Application Number:
  US08/206,791
• Time in Patent Office: 915 Days
• Field of Search: 264/106, 264/107, 264/154, 264/155, 264/161, 264/326.1, 425/810.3, 425/554, 425/289, 425/DIG. 51
• US Class Current: 264/106
• CPC Class Codes: B29C 2045/1745 using vacuum means
• CPC Class Codes: B29C 2045/1746 using magnetic means
• CPC Class Codes: B29C 2045/2638 Magnetic means for mounting stampers
• CPC Class Codes: B29C 45/263 with mould wall parts provided with fine grooves or impressions, e.g. for record discs
• CPC Class Codes: B29C 45/2632 Stampers; Mountings thereof
• CPC Class Codes: G11B 7/263 Preparing and using a stamper, e.g. pressing or injection molding substrates production of optical record carriers, e.g. optical discs B29D17/005
• CPC Class Codes: Y10S 425/051 Sprue removal
• CPC Class Codes: Y10S 425/06 Vacuum
• CPC Class Codes: Y10S 425/81 Sound record

Abstract

An improved method for forming a disc substrate having a bottomed centering hole for rotating and driving the disc. The method includes injecting synthetic resin into a mold cavity formed by a first and second metal molds to form the substrate, and punching at least part of the centering hole by a movable member protruded into the mold cavity to form a through-hole. A stamper containing digital information is held in place inside the mold cavity by its inner circumference by means of a vacuum or a magnet.

Claims

1. A method for forming in a mold cavity created by a first metal mold and a second metal mold a disc substrate having a bottomed centering hole and a reference loading plane for disc rotating and driving means, the reference loading plane being substantially parallel to a planar region on which a light beam is incident, the reference loading plane being projected from the planar region, comprising the steps of:

holding a radially outer edge of a stamper in the mold cavity against an outer edge of the first metal mold with a holder attached to the first metal mold;

holding a radially inner side of the stamper to the first metal mold;

injecting synthetic resin into the mold cavity for forming the bottomed centering hole, wherein the bottomed centering hole is formed by a stationary member protruding into the mold cavity; and

punching at least a part of the bottomed centering hole by a movable member protruded into the mold cavity for forming a through-hole.

2. The method as defined in claim 1 wherein the through-hole is formed by moving the movable member from the reference loading plane.

7. The method as defined in claim 2 wherein said stationary member has a center and said movable member is provided at said center of said stationary member.

3. A method for forming in a mold cavity created by a first metal mold and a second metal mold a disc substrate having a bottomed centering aperture and a reference loading plane for disc rotating and driving means, the reference loading plane being substantially parallel to a planar region on which a light beam is incident, the reference loading plane being projected from the planar region, comprising the steps of:

holding a radially outer edge of a stamper in the mold cavity against an outer edge of the first metal mold with a holder attached to the first metal mold;

holding a radially inner side of the stamper to the first metal mold;

injecting synthetic resin through a sprue bushing into the mold cavity for molding the disc substrate, and

pushing the sprue bushing out of the mold cavity while simultaneously punching through a central region of the molded disc shaped substrate by projecting a movable member through the second metal mold into the mold cavity for forming the bottomed centering hole in the disc shaped substrate.

5. A method for molding a disc shaped substrate as recited in claim 3 wherein said attracting step comprises applying a vacuum between the stamper and the first metal mold.

6. A method for molding a disc shaped substrate as recited in claim 3 wherein said attracting step comprises applying a magnetic force between the stamper and the first metal mold.

8. The method as defined in claim 3 wherein the bottomed centering hole is formed by a stationary member having a center that protrudes into the mold cavity and said movable member is provided at said center of said stationary member.

4. A method of molding a disc shaped substrate having a projection, the projection being formed in a central portion of the disc shaped substrate and having a through-hole, the method comprising the steps of:

moving one of a first metal mold and a second metal mold mounted facing the first metal mold toward and away from the other of the first metal mold and the second metal mold, the second metal mold defining a mold cavity between it and the first metal mold;

holding at an outer edge of the mold cavity a radially outer side of a stamper mounted on the first metal mold and arranged within the mold cavity and being attached to the first metal mold;

attracting a radially inner side of the stamper to the first metal mold;

positioning the stamper by engaging a resin injecting sprue bushing with the central aperture in the stamper;

injecting resin into the mold cavity via the sprue bushing to form the disc shaped substrate; and

pushing the sprue bushing out of the mold cavity while simultaneously punching through a central region of the molded disc shaped substrate by projecting a movable member into the mold cavity for forming the through-hole in the disc shaped substrate.