Roll-up curtain, particularly for cars

The roller shutter comprises a band (2) which can be wound around a rotating part (3). There is a rotor (13) on the rotating part and means for slowing the rotation of the rotor in the winding direction. A stator (15) is provided on a complementary part (4) which is fixed to an external point relative to which the rotating part is mounted. The rotational slowing means comprises a frictional viscous substance in the space between the rotor and stator.