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The layout of a typical Bayfol® HX film consists of a light-sensitive photopolymer layer coated onto a transparent substrate and protected on the other side by a cover film. The substrate is particularly beneficial, not only for easy handling of the film during holographic recording, but also for further mechanical processing steps which are required to embed the film into a finished optical component. However for certain applications it is desirable to remove the substrate before or after recording. This will allow the user to make full use of the high flexibility of the photopolymer layer, for example if it comes to curved surfaces that have to be covered. Also more complex stack geometries can be realized in which the photopolymer layer could be embedded in optically well designed cavities or mechanically demanding setups. To facilitate this, we developed Bayfol® HX film grades in which the substrate has a lower adhesion to the photopolymer layer compared to the protective cover film. Therefor the substrate can be removed first in contrast to existing Bayfol® HX film grades which only allow to remove the protective cover film. On the other hand the adhesion of the protective cover film can also be well controlled, so that it can be specifically selected according to the needs of the surface to which the photopolymer layer has to be transferred to. In this paper we demonstrate versatile application processes making use of these transfer grades of Bayfol® HX films with respect to adhesion design, integration in complex stacks and application on curved surfaces. |
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