Dynamic information storage or retrieval – Storage medium structure – Layered
Reexamination Certificate
1999-12-29
2004-01-13
Letscher, George J. (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Layered
C264S294000
Reexamination Certificate
active
06678238
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to the field of data storage, and more particularly to a method and apparatus for manufacturing disk-shaped articles for storing data.
BACKGROUND
Conventional molds for manufacturing substrates for data-storage disks typically include a moveable side and a fixed side that when closed, form at least in part the boundaries of a disk shaped cavity. A stamper, typically located on the moveable side of the mold, is used to impart a surface profile onto the formed article or substrate. During the manufacturing process, replacement of the stamper may be necessary to retool the mold for a new product or may be required to assure part quality and, in some cases, stamper changeover occurs frequently.
It is often difficult and time consuming to replace the current stamper in conventional systems. For example, conventional systems often include a holder for clamping the stamper within the mold. The holder is typically retained in place using a mechanical fixture. When the stamper requires replacement, the mechanical fixture is removed to release the holder, the stamper is removed and a new stamper is inserted. The holder is again fixtured into place. This can be a time consuming process especially in applications requiring frequent changeover.
Another characteristic of conventional systems is the difficulty involved in removing the substrate from the mold after molding. One solution has been to use a demolding feature for removing the substrate from the mold. The demolding feature provides pressurized gas directly onto the back face of a substrate to facilitate removal of the disk. The pressurized gas is applied through a set of openings through the wall of the mold cavity. The location of the openings on the wall of the mold is on the side of the mold cavity opposite the stamper. Such a configuration allows passage of mold resin into the openings of the demolding feature during the molding process. Passage of mold resin into these openings or cavities in the wall of the mold cavity can adversely affect the flatness of the substrate.
An additional problem with conventional systems is that cavities may be created between mold components due to those components having different rates of thermal expansion. During the course of operation of a typical mold, temperature of the mold components may vary between room temperature and 130 degrees Celsius or more. Resin flowing into these cavities can also affect process control over thickness, flatness, concentricity, and inner and outer diameter of the formed disk.
Conventional molds have typically been used to produce substrates for disks having information on one side. Disks having information on both sides are typically formed by bonding two single-sided disks with a layer of adhesive. Thus disks having information on both sides, have a tolerance stack up that includes the variation found in each of the two disks and the variation found in the adhesive bond between the disks. Thus it is more difficult to maintain the various process indicia such as thickness, flatness, concentricity and outer diameter when producing double-sided disks.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a mold improving the ease of stamper changeover. Furthermore, there is a need for a substrate and final storage article having improved process indicia such as thickness, flatness, concentricity and inner and outer diameter.
SUMMARY
Described herein is an improved mold that addresses the above-described deficiencies found within conventional molds. For example, in one embodiment, the invention is directed to a mold for manufacturing disks and includes a holder that extends over a portion of a stamper. A vacuum line applies a vacuum force on the backside of the holder in order to maintain placement of the holder against the stamper. In another embodiment, the mold includes a demolding line that applies a demolding force to aid in separating the substrate from the stamper. The molds of the various embodiments can be used in the production of single-substrate double-sided articles for storing data on both sides of the data storage article.
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Novotny Jeffrey M.
Plourde Douglas R.
Sandstrom Chad R.
Sitz Dean E.
Imation Corp.
Letscher George J.
Levinson Eric D.
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