Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Patent
1999-08-11
2000-12-19
Gorgos, Kathryn
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
205118, G11B 724, C25D 502
Patent
active
061635235
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for producing a press-form (stamper)for shaping an information-carrying optical storage medium (compact disk, CD), whereby in one process step tracks are burned by means of a laser beam into the surface of a blank covered with a covering layer, according to the information to be stored, before the tracks are filled with metal in an electroplating process, in a further process step.
Essentially two methods for producing a stamper are known. In a first method ("Photoresist Mastering") a blank in the form of a glass plate with a photosensitive surface is exposed to a focused laser beam. During the chemical development of the photosensitive surface, the exposed portions develop depressions, while the surface between the exposed portions is not affected. In another method("Non Photoresist Mastering") the blank is coated with a layer of organic material (organic dye). In this layer depressions are directly burned, respectively melted by means of a laser beam.
The glass master produced in one of the mentioned ways is coated with a thin metallic layer, before the depressions are filled in an electrolytic process and a base is formed thereon (electroforming). The base with the raised data structures is separated from the glass master and cleaned and then used as a stamper.
The finishing of the CDs takes place in an injection molding chamber, wherein optical polycarbonate is sprayed under pressure onto the stamper. Afterwards the stamper and the finished CDs are separated from each other by compressed air and the surface of the CDs is covered with a reflective coating and lacquered.
The drawback of the known methods is that they are complicated and expensive due to the numerous process steps. Besides the stampers made through electroforming have a relatively short life, since the metal applied in the electroplating process has little strength. So for instance with one stamper merely a few thousand CDs can be pressed, before the quality of the stamper is lost because of the extreme conditions in the injection molding machine (1800 gauge pressure and 380.degree. C.).
It is the object of the invention to create a method by means of which, with little time and expenses, a resistant stamper for forming of optical storage media (compact disks) can be produced.
This object is achieved due to the fact that the covering layer rests on a metallic surface.
Thereby it is particularly advantageous to make the blank into a metallic disk, particularly of sheet metal. Due to the method of the invention, it is possible to produce stampers in a cost-effective manner, thereby reducing the costs of producing compact disks. This cost savings is a result of a reduction in the number of process steps. So for instance on the one hand the finishing of the raw glass plate is eliminated, and on the other hand the energy-intensive electroforming process is replaced by an electroplating process which consumes less current, wherein considerably less metal has to be deposited.
The stampers produced with the method of the invention are particularly resistant, since their base plate consist of cold-rolled sheet metal, which is commercially available in a state of high purity and with a reflecting surface. As a metal for the blank preferably nickel with a purity of particularly 99.5% is used. Due to a densified crystalline structure, the rolled nickel sheet is harder than the metal deposited during electroforming. The rolled sheet metal has only to be stamped out or cut in the desired shape. However the quality of the metallic blank can be further improved by grinding and polishing.
The clean metallic disk is preferably provided on the surface to be inscribed at first with adhesive ground (primer), which insures a good hold of the subsequently to be applied lacquer layer and which prevents acid penetration under the lacquer in the electroplating bath. In order to achieve an even distribution of the lacquer layer to be applied on the primer, the lacquer or a resin is sprayed in a centrifuge on the metallic blank. Th
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patent: 4729940 (1988-03-01), Nee et al.
patent: 5147763 (1992-09-01), Kamitakahara
patent: 5283159 (1994-02-01), Norton et al.
patent: 5494782 (1996-02-01), Maenza et al.
patent: 5509991 (1996-04-01), Choi
Dubno Herbert
Gorgos Kathryn
Innovators AG
Smith-Hicks Erica
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