Film coating operational boundaries

Figure 3 Outline of the operational boundaries of a film-coating process.

The inherent complexities of this process are well illustrated by the process operational boundaries highlighted in Figure 3. Although this diagram specifically references tablet coating in a side-vented pan, the concepts are applicable to the film coating of all types of products in a wide variety of coating machines. 

Small molecules are usually evaporated in vacuum while polymeric semiconductors are solution processed and deposited, usually, by spin coating. In order to prevent operational failures, grain boundaries and aggregation should be avoided. Amorphous films are usually desired in order to have better performances for devices operating below the polymer glass temperature. As discussed later, oriented systems with polarized emission are requested for specific applications. 

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