At HARMAN technology Ltd we are applying the technology we have learnt in decades of experience in the photographic field in other areas.
DONOR WEB COATING (Decal)
For a multitude of reasons donor webs are used throughout industry. They are usually needed when a product cannot be assembled by a process in which the active layer(s) are applied directly to the final substrate or surface. This may be due to an incompatibility within the design or to a process problem that has to be overcome. For example, it may be impossible to subject the final substrate to a conventional process, or the receiving layer surface may not be uniform, or the active layer or layers may need to be applied to a range of different final surfaces (where one standardised coating could be used and transferred onto the different substrates).
With HARMAN technology Ltd multilayer coating capabilities we can coat a layer or set of layers onto the appropriate donor web at the same time as the necessary supporting release or key coat/ adhesion layers, for onward deposition onto the final surface (known as Decal Transfers).
This secondary deposition of the functional layer(s) could be achieved by activation of a thermoplastic polymer (for example at an elevated temperature, as in a conventional lamination or iron on process), or under pressure.
The type of Donor web can handle is any flexible substrate that can be transported, coated, and dried through our coating machine. As long as the functional layer(s) have sufficient temporary adhesion to that web, a donor web can be produced. However, the actives and support layer chemistries must be aqueous based.
The picture shows a method of applying an active layer to a substrate that is far too porous / absorbent to be coated conventionally. The top picture shows a microscopic cross section of the donor web, with the active layer at its surface, applied to the substrate. The lower picture shows the donor web removed, leaving behind the active layer.
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