Abstract: The passive liquid-crystal flat screen which can be projected onto a screen has a flat screen (50) to which an electronic control unit (52) is attached and two polarization filters (36, 38) both of which are located in the light path (arrow 54), the one in front of, and the other behind, the flat screen (50). Both the polarization filters (36, 38) are positioned at such a distance from the flat screen (50) that between the flat screen (50) and each of the polarization filters (36, 38) there is formed an air tunnel or canal in which a current of air flows which impinges on the inner surfaces of the polarization filters (36, 38) and the flat screen (50) and cools these components.