Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-12-22
2003-03-11
Lorengo, J. A. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S233000, C156S234000, C156S238000, C156S247000, C156S272200, C156S289000, C427S146000, C427S208200, C427S314000, C427S457000, C428S040100, C428S042100, C428S042300, C428S200000, C428S204000, C428S347000, C428S914000
Reexamination Certificate
active
06531016
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a process for the region-wise transfer of the decorative layer of a transfer foil, which decorative layer includes an adhesive layer which is activatable by radiation energy, from a carrier film for the decorative layer onto a substrate using a possibly heated stamping tool, wherein the adhesive layer is at least partially activated before the transfer foil passes into the stamping tool.
The invention further concerns a transfer foil which in particular is suitable for use in the transfer process according to the invention, which on a carrier film has a decorative layer which comprises a plurality of layer portions and which can be transferred region-wise onto a substrate under the action of pressure and possibly heat and whose surface that is remote from the carrier film is formed by an adhesive layer which is activatable by radiation energy.
When transferring the decorative layer of a transfer foil onto a substrate, it is necessary for the adhesive to be sufficiently activated in order to attain adequate adhesion of the decorative layer on the substrate. In that respect, the time required for activation of the adhesive layer quite crucially determines the speed of passage through the corresponding application machines.
In order to increase the machine speed, it is already known from WO 96/37368 for the heat-activatable adhesive layer of the decorative layer of a stamping or embossing foil to be preheated prior to the actual stamping or embossing operation in order in that way to at least partially activate the adhesive layer. In the known process—as usual—transfer of the decorative layer onto the substrate is effected in the regions in which the stamping tool acts on the stamping foil, while WO 96/37368 provides that the stamping tool is also heated. That procedure admittedly allows higher machine speeds to be attained. There is however the risk that, for example when the adhesive is excessively preheated, neat and clean region-wise application of the decorative layer to the substrate gives rise to difficulties because the decorative layer adheres to the substrate not only in the regions in which the stamping tool acts on the decorative layer but possibly also outside those regions, if the adhesive already has a sufficiently strong adhesion effect. That problem can occur in particular when using comparatively thick decorative layers, or decorative layers which are of a comparatively high level of mechanical stability and which for example have a metallisation thereon.
EP 0 741 370 B1 discloses a process for applying a security element to a substrate, in which the adhesive layer is brought into contact with the substrate and locally heated by the application of energy through the laminate structure, that is to say through the decorative layer, thereby seeking to provide that the decorative layer adheres to the substrate only at the heated locations, without any structures of the decorative layer being destroyed. In accordance with EP 0 741 370 B1, either laser radiation or light sources are used for the supply of energy. A laser beam can be guided in accordance with the desired pattern. When using light sources, the procedure involved has recourse either to masks or to exposure with addressable arrays consisting of laser or light emitting diodes. That known process certainly has the advantage that a very neat and clean and nonetheless only region-wise transfer of the decorative layer of a transfer foil from the carrier film of the transfer foil onto a substrate is possible, while the use of pressure in implementing transfer onto the substrate is substantially eliminated, to provide for careful treatment of the structures which are possibly present in the decorative layer. A disadvantage of that known procedure however is that comparatively low operating speeds must be reckoned to apply. When using masks or diode arrays, it even necessary under some circumstances to move the transfer foil and the substrate with a stepwise movement so that the mask or the array is stationary relative to the transfer foil, during the time required for activation of the adhesive layer.
SUMMARY OF THE INVENTION
Now, the object of the invention is to propose a process and a transfer foil which is suitable in particular for carrying out that process, with which there is on the one hand the possibility of increasing the machine speed by pre-activation of the adhesive layer, but at the same time also ensuring that neat and clean transfer of the decorative layer of the transfer foil also occurs only in the regions which are actually to be transferred.
In accordance with the invention, to attain that object, it is proposed that the process of the general kind set forth is so developed that before the transfer foil passes into the stamping tool the adhesive layer is activated by means of radiation energy only in the surface regions in which the decorative layer is to be transferred onto the substrate by means of the stamping tool.
In contrast to the teaching of WO 96/37368 in which pre-heating of the adhesive layer of the transfer foil is effected over substantially the entire surface area before it passes into the stamping tool, the present invention proposes that pre-heating—similarly to the basic proposal of EP 0 741 370 B1—is effected only in a region-wise manner, in which respect however it is important that in actual fact preheating takes place before passing into the stamping tool. The process according to the invention therefore involves operating not only with activation of the adhesive but at the same time also by means of a suitable stamping tool, that is to say using suitable pressure.
By virtue of the additional application of pressure, it can very frequently be provided that a comparatively low level of radiation energy is already sufficient to pre-activate the adhesive to such an extent that the machine speed can be substantially increased. At the same time, region-wise pre-activation of the adhesive layer ensures that neat and clean region-wise stamping occurs, because the working conditions can be easily selected in such a fashion that the decorative foil adheres by way of the adhesive layer to the substrate only where the adhesive layer was actually also preheated.
It is particularly advantageous if the process according to the invention involves using a transfer foil whose decorative layer has an absorption layer only in the surface regions to be transferred onto the substrate, which absorption layer absorbs the radiation energy for effecting activation of the adhesive layer.
The transfer foil is therefor advantageously such that, in the surface regions to be transferred, it includes an additional layer portion, namely the absorption layer. Pre-activation of the adhesive layer then occurs only in the region of that absorption layer which suitably absorbs the radiation energy—and which naturally must be transferred to the adhesive layer—, wherein it is possible in that way, without involving particular apparatus complication and expenditure, to provide that the adhesive layer is pre-activated in actual fact only in the regions that are wanted. In particular, it is possible in accordance with the invention to eliminate the use of especially guided laser beams, as well as masks or diode arrays which are provided in accordance with EP 0 741 370 B1.
The effect of region-wise activation can be further improved in particular in the case of a transfer foil whose decorative layer is provided region-wise with an absorption layer, if the radiation energy for activating the adhesive layer acts on the decorative layer only in the surface regions which are intended for transfer onto the substrate, wherein the radiation energy for activating the adhesive layer advantageously acts by way of a mask or the like only on the surface regions of the decorative layer and adhesive layer, which are to be transferred onto the substrate.
In principle, it is possible to envisage using all possible kinds of activation of the adhesive layer. However, a procedure w
Brehm Ludwig
Weber Klaus
Hoffmann & Baron , LLP
Leonhard Kurz GmbH & Co.
Lorengo J. A.
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