Pros and cons of release methods
The different methods of release have different merits and limitations. It is usually preferred for the substrate or coating to have zero residue left from the release layer. From an economic perspective, it is often preferable to be able to use the carrier material multiple times. Both of these requirements add to the challenge. Waxes or inorganic materials that are either melted or dissolved are hard to fully remove from each surface. Any release layer left behind can be a weakness where the surface has to be adhered to another surface or the surface has to be coated. If the release layer has been unevenly removed, it also may result in a rougher surface that may be another problem on the line.
If the release layer has not been degraded during the first processing, the carrier substrate may require only a new release layer to be applied for the carrier to be used again. If an organic layer has been used as a release layer where the monomer has been partially polymerized, it may need additional processing to polymerize the coating and so create a new surface before the new release layer can be applied. This may change the quality of the release layer on the carrier each time it is used which can make the process harder to predict.
Reducing winding defects
Carrier webs, while adding to the material cost, can enable an unstable web that would be distorted by the winding process to be constrained such that the carrier web provides the stable platform on which the winding tension can be safely applied.
Carrier webs are the unsung hero to the vacuum R2R-coating industry. They are an enabling technology that expands the range of materials that can be web-processed. The range of products that I have seen use this technology has gone from flake pigments that start down at the nano-scale through to roofing tiles at some seven to eight orders of magnitude larger in size.