WE CLAIM
1. An improved sputtering machine for coating optical discs including a sputtering unit having means on which said discs rest during said sputtering operation and an assembly for holding said discs in position during sputtering operation wherein said means are coated with a teflon coating so that generation of PC dust, by contact between said means and optical discs during sputtering operation is reduced, said contact being caused due to misalignment of said means during sputtering operation.
2. The sputtering machine as claimed in claiml, wherein said means comprises a center ring.
3. The sputtering machine as claimed in any of claims 1 to 2 wherein said assembly comprises a spring loaded ball assembly having a plurality of spring loaded balls.
4. The sputtering machine as claimed in any of claims 2 to 3 wherein said optical discs are placed in position by any automated means in an automated manufacturing environment and said ring is operatively engaged to and driven/rotated at desired RPM by an electric means.
5. The sputtering machine as claimed in any preceding claim wherein said electric means comprises a DC motor.
6. A method for coating optical discs by sputtering operation when carried out by applying the sputtering machine as claimed in any preceding claim. 7.0ptical discs having uniform coating, obtained by the method as claimed in claim 6.

AN IMPROVED SPUTTERING MACHINE FOR EFFICIENT COATING OF OPTICAL DISCS AND A METHOD FOR COATING OPTICAL DISCS APPLYING THE SPUTTERING MACHINE
FIELD OF THE INVENTION
The present invention, in general relates to an improved sputtering machine for efficient coating of optical discs and in particular, to coating the means on which the optical discs rest during sputtering operation, with a teflon coating, so that generation of PC dust by contact between said means and the optical discs, during sputtering operation is reduced thereby ensuring improvement of quality of the overall process. BACKGROUND OF THE INVENTION
It is well known in the art that sputtering is a PVD (physical Vapour Deposition) process adopted for coating a reflective layer on the optical discs. Traditionally, sputtering machine is used for coating a reflective layer on optical discs. The sputtering machine contains inter alia a sputtering unit having an assembly for holding on to the optical discs during sputtering and means on which the optical discs rest during the sputtering process. Such means is usually a sputter center ring but is not limited to it and includes all other means that would be common to persons skilled in the art. All through out the specification such means is referred to as sputter center ring, purely for the sake of understanding and is not limited to it and rather, it includes all other means as should be clear to persons skilled in the art. The process of sputtering being a very fast one, it is immensely important to keep the optical discs in a correct alignment as otherwise, the uniformity of the coating is greatly hampered, which results in loss of production and compromised product quality. The sputtering assembly plays a vital role in this respect which may comprise a spring loaded ball assembly having a plurality of spring loaded balls.
The sputtering unit has a sputter center ring as stated aforesaid. The state of the art sputter center rings are made of stainless steel. The optical discs rest particularly on this sputter center ring during the sputtering process. During sputtering there is a fast vertical movement of the ring and there is lesser cycle time. Due to fast vertical movement and resulting lesser cycle time, many a time the sputter ring becomes misaligned. This results into generation of PC dust. When the sputter ring becomes misaligned, it comes in contact with or hits the center hole of the optical disc. This not only impedes the whole process but the PC dust also deteriorates the overall quality of the process. Further PC dust so generated gets stuck in the ball bearing of the sputter assembly to further generate PC dust and therefore it magnifies the problem. This, also hampers the uniformity, of the resultant reflective coating on the optical discs.
Hence, there was a long felt need to design a sputtering machine which can reduce the generation of PC dust during sputtering operation, by contact between sputter center ring and optical discs, during sputtering operation.
Objects of the Invention
It is a prime object of this invention to provide an improved sputtering machine having improved means on which optical discs rest during sputtering operations.
It is another object of the present invention to reduce the PC dust generated during the sputtering process.
It is a further object of the present invention to improve the overall quality of the method of coating optical discs, by sputtering.
Yet, another object of the present invention is to provide better quality optical discs, with uniform reflective layer coating.
The above objects and other aspects of the present invention will be better understood from the following description which is purely by way of understanding and not by way of any sort of limitation. Summary of the Invention
Accordingly, the present invention provides an improved sputtering machine for coating optical discs including a sputtering unit having means on which said discs rest during said sputtering operation and an assembly for holding
said discs in position, during sputtering operation wherein said means are coated with a teflon coating so that generation of PC dust, by contact between said means and optical discs during sputtering operation, is reduced, said contact being caused due to misalignment of said means , during sputtering operation.
In accordance with preferred embodiments of the sputtering machine of the instant invention:
-said means comprises a center ring.
-said assembly comprises a spring loaded ball assembly having a plurality of spring loaded balls.
-said optical discs are placed in position by any automated means in an automated manufacturing environment and said ring is operativeiy engaged to and driven/rotated at desired RPM by an electric means, -said electric means comprises a DC motor.
The present invention also provides a method for coating optical discs by sputtering operation when carried out by applying the sputtering machine as described hereinbefore..
The present invention also provides optical discs having uniform coating, obtained by the method as above.
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 purely by
way of illustration and not by way of any sort of limitation. In the drawings
accompanying the Provisional Specification :
Figure 1 shows the prior art sputtering center ring;
Figure 2 shows the sputtering center ring of the instant invention.
Detailed Description of the Invention
It is known in the art that sputtering machine is used to undertake sputtering operation for the purpose of coating a reflective layer on optical discs. Usually for this purpose, as stated hereinbefore, the sputtering machine contains a sputtering unit having an assembly for holding on to the optical discs during sputtering and means on which the optical discs rest during the sputtering process. Such means is usually a sputter center ring but is not limited to it and includes all other means that would be common to persons skilled in the art. The process of sputtering being a very fast one, it is immensely important to keep the optical discs in a correct alignment as otherwise the uniformity of the coating is greatly hampered which results in loss of production and compromised product quality. The sputtering assembly plays a vital role in this respect which may comprise a spring loaded ball assembly having a plurality of spring loaded balls.
The optical discs may be placed in position during sputtering by any automated means, such as a robotic arm, in an automated manufacturing environment. The sputter center ring may be operatively engaged to and driven/rotated at desired RPM by an electric means, such as a DC Motor. Now, during sputtering operation, due to fast vertical movement and resulting lesser cycle time, the sputter center ring gets misaligned and hits the center hole in the optical discs, resulting in generation of PC dust. The sputtering unit has a sputter center ring as stated aforesaid, on which optical discs rest during sputtering operation. The state of the art sputter center rings are made of stainless steel. To reduce the PC dust which is generated, in the event of the sputter ring becoming misaligned due to fast vertical movement and hitting the center hole in the optical disc, the sputter ring is provided with a Teflon coating. It has been found that with such Teflon coating the on the sputter ring, even if the sputter ring comes in contact with the central hole of the optical discs, generation of PC dust is minimal. The improvement is in fact dramatic and beyond the expectation. This technical advancement was hitherto unknown and not conceived by persons skilled in the art. Decrease in PC dust results also decrease in the clogging of the ball bearing.
This improvement with the Teflon coated sputtering unit greatly improves the
overall yield of the process. This also improves the visual appearance of the optical discs by ensuring uniform reflective layer quoting. 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 hereinbefore and what has been claimed hereinafter.