A screen that can be operated in a first operating mode B1 for a free viewing mode, and a second operating mode B2 for a restricted viewing mode, comprising - an image display unit, - a plate-shaped, transparent light guide disposed in front of the image display unit as seen in the viewing direction, and - light sources arranged laterally at edges of the light guide, - wherein - the light guide has a haze value of less than 20%, measured according to ASTM D1003, - wherein in operating mode B1 the light sources are switched off, so that the light originating from the image display unit, with image information modulated upon it, passes the light guide essentially unaffected, and - wherein in operating mode B2 the light sources are switched on, and, in a first alternative, either due to scattering particles distributed in the light guide in space or regarding their concentration, or due to outcoupling elements arranged on at least one of the large faces of the light guide, a light-radiating characteristic is produced at which the average luminance, measured at angles α relative to the surface normal of the at least one large face of the light guide with 0° ≤ α ≤ θ, is, with 10° ≤ θ ≤ 60°, smaller at least by a factor X, with X ≥ 1.2, than the highest measurable luminance on the same large face of the light guide, radiated at angles α > θ relative to the surface normal, or wherein, in a second alternative, the image display unit has a light-radiating characteristic at which the luminance achieved in the direction of the surface normal of the image display unit is higher than that achieved at an angle of α ≥ θ relative to that surface normal, - so that in operating mode B2 the light originating from the image display unit, with image information modulated upon it, is superimposed by light radiated by the surface of the light guide over a wide angular range, whereby, from viewing angles α > θ, the visibility of the image information presented on the image display unit is diminished or even prevented. - an image display unit, - a plate-shaped, transparent light guide disposed in front of the image display unit as seen in the viewing direction, and - light sources arranged laterally at edges of the light guide, - wherein - the light guide has a haze value of less than 20%, measured according to ASTM D1003, - wherein in operating mode B1 the light sources are switched off, so that the light originating from the image display unit, with image information modulated upon it, passes the light guide essentially unaffected, and - wherein in operating mode B2 the light sources are switched on, and, in a first alternative, either due to scattering particles distributed in the light guide in space or regarding their concentration, or due to outcoupling elements arranged on at least one of the large faces of the light guide, a light-radiating characteristic is produced at which the average luminance, measured at angles α relative to the surface normal of the at least one large face of the light guide with 0° ≤ α ≤ θ, is, with 10° ≤ θ ≤ 60°, smaller at least by a factor X, with X ≥ 1.2, than the highest measurable luminance on the same large face of the light guide, radiated at angles α > θ relative to the surface normal, or wherein, in a second alternative, the image display unit has a light-radiating characteristic at which the luminance achieved in the direction of the surface normal of the image display unit is higher than that achieved at an angle of α ≥ θ relative to that surface normal, - so that in operating mode B2 the light originating from the image display unit, with image information modulated upon it, is superimposed by light radiated by the surface of the light guide over a wide angular range, whereby, from viewing angles α > θ, the visibility of the image information presented on the image display unit is diminished or even prevented.