AN IMPROVED METHOD OF MANUFACTURING OPTICAL DISCS AND OPTICAL DISCS MANUFACTURED BY THE METHOD

FIELD OF THE INVENTION

The present invention in general, relates to an improved method of manufacturing optical discs and in particular, to application of diamond like or other non-stick (like organic mono layers) coatings on stampers, for replication
of optical discs.

BACKGROUND OF THE INVENTION

Replication of optical discs by application of stampers is a very common technique involved in the manufacturing process of optical discs.
The present invention relates to BD-stampers (BD-R, BD-RE and BD-ROM) and DVD (R, RW and ROM) stampers, used for replication of optical discs.

In the manufacturing methods of optical discs known in the art, for BD-stampers, the groove depth and width are becoming so small, that minor irregularities and defects have started to crop up and hamper the replication process and
consequently, the quality of the discs. In the stampers, often defects like pinholes are getting detected. These pinholes originate during the galvanic process and are very difficult to control. Other irregularities like nano-roughness, crop up during the operation of several steps, in the mastering and galvanic process. All these defects and irregularities have a negative effect on the replication process, resulting in quality issues on the discs like high symbol error rate and and
tracking issues. Furthermore, it has been observed that pin-holes in the stamper
grooves as well as the nano-roughness, if any, are replicated into the discs.

These defects affect the optical signal during writing and reading of the discs.

For DVD stampers, the problem arising out of the defects and irregularities, as discussed aforesaid are also prevalent, although to a lesser degree, as compared to BD stampers, due to the larger wavelength of the laser used and
the larger dimensions of the grooves.

Attempts have been made to sort out the above issues, like high symbol error rate and tracking issues, due to pin-holes, nano-roughness which affects the optical signal during writing and reading of the discs, but significant results were not achieved, particularly due to the fact that the root cause could not be detected.

Accordingly there was a long felt need to develop a technology which would nullify the defects cropping up during the process of replication of optical discs by application of stampers , involved in the manufacturing process of optical discs, the main defects being, high symbol error rate and tracking issues, due to pin¬holes, nano-roughness which affect the optical signal during writing and reading of the discs.

The present invention meets the aforesaid need as exemplified hereinafter. All through out the specification reference has been made to optical discs for the sake of understanding, but is not to limited to it and the present invention embraces all similar items in the related fields, as may be understood by persons skilled in the art.

OBJECTS OF THE INVENTION

It is a prime object of the present invention to provide an improved method for manufacturing optical discs, whereby, defects cropping up during replication of optical discs by application of stamper are nullified.

It is a further object of the present invention to provide an optical disc obtained by an improved method for manufacturing optical discs whereby, defects cropping up during replication of optical discs by application of stamper are nullified. It is yet another object of the present invention to provide an improved method of manufacturing optical discs which includes application of an improved stamper for replication of optical discs whereby defects in the final product, such as high symbol error rate and tracking issues, due to pin-holes, nano-roughness which affect the optical signal during writing and reading of the discs are nullified.

It is a further object of the present invention to provide an improved optical disc devoid of problems such as high symbol error rate and tracking issues, due to pin-holes, nano-roughness, which affect the optical signal during writing and reading of the discs.

It is a further object of the present invention, to provide an improved mastering and galvanic process involved in the manufacturing process of optical discs whereby, the overall quality of the final product is enhanced and the manufacturing cost is also reduced.

It is a further object of the present invention to fabricate an improved stamper for its application during replication of optical discs, involved in manufacturing process of optical discs, whereby the overall quality of the final product Is enhanced and the manufacturing cost is also reduced.

How the foregoing objects are achieved and the other aspects of the present invention will be clear from the following description, which Is purely for the sake of understanding and not by way of any sort of limitation.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an improved method for manufacturing optical discs including dyeing, sputtering, optionally bonding and replication of optical discs, wherein said replication is carried out by application of
a stamper having a non-stick coating on its surface, whereby defects In the final
product, such as high symbol error rate and tracking Issues, due to pin-holes,
nano-roughness, which adversely affect the optical signal during writing and
reading of the discs, are nullified.

In accordance with preferred embodiments of the method of the present invention:

-said stamper has a coating of Diamond-Like-Carbon (DLC).

-said stamper has a non-stick coating of at least an organic mono-layer.

The present invention also provides an improved optical disc, obtained by the method as described herein above, whereby said optical disc is devoid of problems such as high symbol error rate and tracking issues, due to pin-holes,
nano-roughness which affect the optical signal during writing and reading of the discs.

The present invention also provides a method of fabricating an improved stamper for its application during replication of optical discs, involved in manufacturing process of optical discs, said method including applying Diamond-Like-Carbon (DLC) or other non-stick (like organic monolayers) coating on the surface of said stamper, whereby the overall quality of the final product is enhanced and the manufacturing cost is also reduced.

The present invention also provides an improved mastering and galvanic process involved in the manufacturing process of optical discs whereby, the overall quality of the final product is enhanced and the manufacturing cost is also
reduced.

BRIEF DESCRIPTION OF THE DRAWINGS ACCOMPANYING THE PROVISIONAL SPECIFICATION

The nature and scope of the present invention will be better understood from the drawings accompanying the provisional specification, which are by way of illustration and not by way of any sort of limitation. In the said drawings:
Figures 1 to 5 graphically exemplify the peaks obtained during the application of various parameters, as detailed in table 1, in that order.

BRIEF DESCRIPTION OF THE INVENTION

The following description is for the sake of understanding the performance of the invention and not by way of any sort of limitation.

As stated aforesaid, application of stamper for replication of optical discs is a very common technology, in the process of manufacturing optical discs. However during such replication process the groove depth and width were becoming so small, that minor irregularities and defects started to crop up and hamper the replication process and consequently, the quality of the discs. Such defects are mainly, high symbol error rate and tracking issues, due to pin-holes, nano-roughness. These defects adversely affect the optical signal during writing and reading of the discs. Such pin holes and nano-roughness are generated mainly during mastering and galvanic process.

By improving the mastering and galvanic process such problems can be taken care of, however, this requires insight in the root cause of these problems, which was hitherto not achievable.
The solution proposed in the present invention, is to overcome the problem by applying a Diamond-Like-Carbon (DLC) or other non-stick (like organic mono layers) coating onto the stamper surface. DLC combines both non-stick properties and excellent wear resistance. The combination of these properties is quite unique. The non-stick properties avoid replication of the small pinholes and irregularities and at the same time avoid building up of contamination (Polycarbonate resin) on the stamper surface. Both effects, improve replica quality both at zero hour, as well as during the life time of the stamper. This technical advancement of application of DLC or other non-stick (like organic mono layers) on BD-stampers or DVD-stampers for applying such stampers during replication of optical discs, for the purpose of removing the defects as aforesaid, was hitherto unknown and not conceivable by persons skilled in the art.

Application of this kind of coatings make stampers less sensitive to contamination during the replication process and improve both the quality of the discs as well as the life time of the stampers, thereby reducing the overall manufacturing cost as well. So, the present invention is economically significant as well.

Table I

The aforesaid table 1 manifests the various results obtained by actual experimentation, which reveals the improvement as described hereinbefore. This is further substantiated, by the graphical representations in Figures 1 to 5, which are self-explanatory.

The present invention has been described with reference to some drawings and preferred embodiments, purely for the sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and claimed in the appended claims.

WE CLAIM

1. An improved method for manufacturing optical discs including dyeing, sputtering, optionally bonding and replication of optical discs, wherein said replication is carried out by application of a stamper having a non-stick coating on its surface, whereby defects in the final product, such as high symbol error
rate and tracking issues, due to pin-holes, nano-roughness, which adversely affect the optical signal during writing and reading of the discs, are nullified.

2. The improved method for manufacturing optical discs as claimed in claim 1 wherein said stamper has a coating of Diamond-Like-Carbon (DLC).

3. The improved method for manufacturing optical discs as claimed in claim 1 wherein said stamper has a non-stick coating of at least an organic mono-layer,

4. An improved optical disc, obtained by the method as claimed in any preceding claim whereby said optical disc is devoid of problems such as high symbol error rate and tracking issues, due to pin-holes, nano-roughness which affect the optical signal during writing and reading of the discs.

5.A method of fabricating an improved stamper for its application during replication of optical discs, involved in manufacturing process of optical discs, said method including applying Diamond-Like-Carbon (DLC) or other non-stick (like organic mono layers)coating on the surface of said stamper, whereby the overall quality of the final product is enhanced and the manufacturing cost is also reduced.

6.An improved mastering and galvanic process involved in the manufacturing process of optical discs including applying the method as claimed in claims 1 to 3 and 5 whereby, the overall quality of the final product is enhanced and the manufacturing cost is also reduced.

7. An improved method for manufacturing optical discs substantially as herein described with particular reference to the drawings accompanying the provisional specification and the tabular results.

8. An improved optical disc substantially as herein described.

9. A method of fabricating an improved stamper for its application during replication of optical discs substantially as herein described with particular reference to the drawings accompanying the provisional specification and the tabular results.