PROCESS AND APPARATUS FOR PRINTING A SURFACE WITH A FLUID

The invention relates to a method for printing a surface (2) with a fluid which contains an organic semiconductor material. The fluid is transported from a storage container (7) through a supply line (5) to a printing head (3), which can be moved over the surface (2), and printed onto the surface (2) by the printing head (3). At least one part of the fluid which is transported through the supply line (5) to the printing head (3) is returned to the storage container (7) via a return line (6), wherein a fluid circuit is formed, and the fluid in the fluid circuit flows through a cleaning device (12) with which the fluid is cleaned. The fluid returned to the storage container (7) flows around and surrounds the fluid being transported in the supply line (5) to the printing head (3) at least in some regions. During the printing process, the storage container (7) is arranged in a fixed location at a distance to the surface (2), and the printing head (3) which is connected to the storage container (7) via a flexible supply line (5) and a flexible return line (6) is moved over the surface (2) for printing purposes.