Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-11-04
2001-07-17
Ball, Michael (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272600, C156S273100, C427S458000, C427S532000
Reexamination Certificate
active
06261403
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of connecting substrate parts, in particular the two halves of a DVD (digital versatile disc) by means of an adhesive.
In DVDs, information which is stored in the form of very small elevations and pits in the surface of one DVD half is read out through the other DVD half as well as the adhesive layer between the two halves. Since the pits are very small, slight flaws in the adhesive layer in the form of small business may impair the reproduction of the information in the pits. Even if there is only a single small bubble in the adhesive layer, the DVD has to be considered defective. There may occur small bubbles even if the substrate part (DVD half) is uniformly coated with the adhesive. It has not been entirely clarified why these small bubbles occur. The small bubbles may be gas inclusions from the ambient atmosphere which are formed when pressing the two substrate parts against each other. There is also the possibility that they are formed in the adhesive by themselves. One reason therefor could be the gas evolution of solvents of the adhesive. Preferably, an adhesive having a specific viscosity is applied to the inner region of a substrate part in the form of a thick circumferential path and is flattened during the connection with the other substrate part, wherein excess adhesive is removed preferably by rapidly rotating the substrate part, i.e., the DVD. Other methods of applying the adhesive are, for instance, uniformly spraying it onto a rotating substrate part or injecting it into two convex substrate parts. In all known methods, the aforementioned small bubbles, which are detrimental to the reproduction of the data, may occur.
BRIEF SUMMARY OF THE INVENTION
An object of the invention is to overcome the aforementioned drawbacks and reliably prevent bubbles, and particularly small bubbles, from being present between the substrate parts after their connection by means of an adhesive.
The above and other objects are achieved by applying electric charges to one or the other part of an optical data carrier, or to an adhesive connecting the parts together. The optical data carrier may be, for example, a DVD.
It has surprisingly been found that the occurrence of small bubbles between two substrate parts after their connection by means of an adhesive can be prevented by the application of charges onto at least one substrate part and/or the adhesive before or after applying the adhesive to a substrate part.
Therefore, according to the present invention, the solution to this problem is based on the concept of applying electric charges to at least one of the substrate parts and/or the adhesive. This may be done before and/or after applying the adhesive and before and/or after connecting the two substrate parts. It is also possible to bond more than two substrate parts (halves) to each other to form a composite of optical data carriers. In this case, the method according to the invention is applied in each of the successive steps of bonding substrate parts to each other.
The advantages of the method according to the invention reside in ensuring a complete and faultless reproduction of the information stored in the pits of the DVD.
It is known per se from DE-A1-37 21 703 to provide work pieces, e.g., car bodies, having an electrically insulating surface with a uniform electrostatic charge prior to lacquering or enameling. Thus, it is possible to uniformly coat the surface with a lacquer or enamel layer. However, the problems occurring in the production of optical storage media, such as DVD, namely the formation of small bubbles, which impair the storage or the reproduction of the data, do not play a role in this state of the art.
In the following, the invention will be explained in more detail by means of the drawings.
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patent: 6004420 (1999-12-01), Nakamura et al.
patent: 6013145 (2000-01-01), Amo et al.
patent: 6165299 (2000-12-01), Guan et al.
patent: 37 21 703 (1989-01-01), None
patent: WO-8905477 (1989-06-01), None
Glasurit-Handbuck Lacke und Farben, Curt R. Vincentz Verlad, Hanover 1984, pp. 604-606.
J.W. Gerstenberg, “Loranatechnik in der Automobilindustrie,” Metalloberflache 51 (12997) 4, pp. 240-242.
H. Gleich, “Verbesserung der Benetzungsfahigkeit durch Plasmabehandlung,” Adhasion 1989, vol. 3 pp. 9-15.
Lexikon der Physik, 3rd ed., Franckh'sche Verlagshandlung Stuttgart, p. 849.
E. Prinz, “Neuere Erkenntnisse uber die Koronaentladung” Coating 1079, pp. 269-272.
Gerigk Reinhard
Muecke Michael
Sichmann Eggo
Ball Michael
Haran John T.
Pillsbury & Winthrop LLP
Singulus Technologies AG
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