Drying and gas or vapor contact with solids – Process – Gas or vapor contact with treated material
Reexamination Certificate
2000-03-22
2001-01-09
Wilson, Pamela (Department: 3749)
Drying and gas or vapor contact with solids
Process
Gas or vapor contact with treated material
C034S448000, C034S267000, C034S274000, C034S276000
Reexamination Certificate
active
06170172
ABSTRACT:
FIELD OF THE INVENTION
The invention is related to the field of adhesive assembly of multi-layer optical information carriers, and specifically DVD disks.
BACKGROUND OF THE INVENTION
The invention relates to a device for curing an adhesive by means of radiation in an at least substantially oxygen-free atmosphere. The adhesive is interposed as an adhesive layer between two superposed layers of a disc-shaped information carrier. The layers together define a peripheral edge of the information carrier. The device includes a radiation source and a supply for a gas, not being oxygen.
Such a device is known and is used in the production of optical information carriers of a type having two substrates glued to one another, at least one of the substrates carrying an information layer. During production a UV-curing polymerizable adhesive is applied, after which the assembly thus formed is irradiated by means of a UV irradiation device in a nitrogen atmosphere. The adhesive then cures by polymerization reactions in which radicals are formed.
DE-A 3642961 refers to the use of UV-curing adhesives as alternatives for epoxy-resin adhesives.
The above citation is hereby incorporated in whole by reference.
SUMMARY OF THE INVENTION
The inventors recognize that a method in which adhesives are cured in a nitrogen atmosphere is not considered to be a suitable mass-production method for optical information carriers because of the intricate equipment that is required.
It is an object of the invention to provide a device of the type defined in the opening paragraph, enabling adhesive layers to be cured during the large-scale production of information carriers.
To this end, the device in accordance with the invention is has a holder for holding the information carrier in a centered position with respect to a centering axis. A gas supply has discharge openings for a gas, not being oxygen, which discharge openings are situated in a circular zone around the centering axis, at a distance from the centering axis which at least substantially corresponds to the radius of the peripheral edge of the information carrier, so as to cause a gas, not being oxygen, to flow past the peripheral edge during curing. Preferably, the discharge openings for inert gas are situated in a wall portion of the device.
It will be evident that the information carrier is stationary while the device in accordance with the invention is used, i.e. while the adhesive layer is being cured.
At least one of the layers to be attached to one another by means of the adhesive, is transparent to the radiation used. In the present context, the term “layer” is to be understood to also a substrate. In principle, the adhesive can be adhesives such as photo-polymerizable acrylates.
In the device in accordance with the invention, an at least substantially oxygen-free atmosphere is created locally, specifically at the peripheral edge of the information carrier, in order to preclude that radicals formed at the periphery during curing are destroyed by reaction with oxygen from the air. It has been found, that in this way, curing of the entire adhesive layer is possible at a comparatively low irradiation intensity. Another advantage, of supplying the gas for the expulsion of the oxygen only at the periphery, is that the supplied gas is used efficiently, as a result of which, the required amount of gas is comparatively small. A suitable gas is preferably an inert gas. Preference is then given to nitrogen but gases such as argon, helium or neon are also suitable. Preferably, the radiation source is a UV source when conventional adhesives are used.
The device in accordance with the invention, can be used successfully in the manufacture of optical discs in accordance with the recently defined DVD standard. Such discs comprise include two substrates connected to one another by means of an adhesive layer, at least one of the substrates being provided with an information layer. In certain versions the adhesive layer should have a specified thickness and should be transparent.
A practical embodiment of the device in accordance with the invention includes a curing chamber having a wall formed with discharge openings. The chamber contains the holder at least during curing and the chamber has discharge openings for gas. For a gas flow directed towards the peripheral edge, the discharge openings are preferably situated opposite the holder, viewed along the centering axis.
In order to guarantee a uniform flow around the information carrier during curing, in the device in accordance with the invention, the holding apparatus form part of a turntable for supporting the information carrier, which turntable comprises a centering means and is rotatable about the centering axis at least during curing. These features further assure a uniform irradiation of the information carrier.
An optimization of the local flow around the information carrier during curing is achieved by means of an embodiment in which the discharge openings are situated in a wall portion of the device. The wall portion extends opposite the holder and has a groove which surrounds the centering axis. The groove contains a plurality of the discharge openings. The presence of the groove, particularly in conjunction with a turntable which is rotated during curing, ensures that a highly oxygen-free gas atmosphere is formed, the peripheral edge being constantly disposed in the supplied gas.
An optimization, of the irradiation of the information carrier during curing, is achieved with an embodiment of the invention having a reflecting wall portion, which extends around the centering axis at a distance from the centering axis greater than the radius of the peripheral edge of the information carrier, so as to aim radiation at the peripheral edge by reflection during curing. These features lead to a reduction of the required power of the radiation source.
An embodiment of the device in accordance with the invention, which enables an information carrier to be loaded into and removed from the curing chamber in a simple manner, a transport unit for moving the holding appartus into and out of the curing chamber.
In an embodiment of the device in accordance with the invention, which is very suitable for mass production, the holder forms part of a collection of holders which can be positioned successively with respect to the discharge openings.
The invention further relates to a method of manufacturing a disc-shaped information carrier having two superposed layers between which an adhesive layer extends. In this connection the invention aims at providing a method which enables an adhesive layer to be cured during the manufacture of an information carrier in mass-production quantities.
The method in accordance with the invention uses the device in accordance with the invention.
The invention moreover relates to a further method of manufacturing a disc-shaped information carrier having two superposed layers between which an adhesive layer extends. In this connection the invention aims at providing a method which enables a highly homogeneous adhesive layer to be formed.
To this end, in the further method in accordance with the invention, an adhesive is applied to one of the layers in two phases, a face of the respective layer being wholly covered with an adhesive during a first phase. After the first phase annular zone of adhesive is formed during a second phase, upon which both layers are moved opposite one another and towards one another and are subsequently pressed onto one another, after which curing of the adhesive is effected. Surprisingly, it has been found that this method of affixing layers to one another, layers being meant to include substrates, makes it possible to form a homogeneous adhesive layer free of gas bubbles. The adhesive is preferably cured by means of the afore-mentioned device in accordance with the invention but the present method is not limited thereto.
During the manufacture of certain information carriers, particularly optical information carriers, such as certain types of DVDs, it is necessary
Brugel Paulus W. J.
Martis Remberto L. T.
Vromans Petrus H. G. M.
Belk Michael E.
U.S. Philips Corporation
Wilson Pamela
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