The tetrahydroquinolines can be prepared by condensing appropriately substituted tetrahydroquinoline aldehydes with suitable substances and subsequently varying the substituents present by customary methods. measured by thermogravimetric analysis. After absorption of the fire retardant composition, non-absorbed fire retardant chemicals are recovered and re-used on subsequent batches of fibers. Each of the surfaces is profiled with first and second sets of grooves which define first and second main directions, respectively, which extend transversely to one another. This way damage caused to the display panel during thin film processing is reduced. A user then selects pixels of the base image overlay for placement in the foreground.