Screen for a free and restricted operating mode

A screen that can be operated in at least two operating modes, a free-viewing mode and a restricted-viewing mode, comprising:

• a backlight extended in a planar manner that, in the free-viewing mode, emits light into an unrestricted angular range, and, in the restricted-viewing mode, emits light in a restricted angular range, wherein light originating from the backlight, in at least one direction lying within an angle greater than 45 degrees relative to a surface normal of the backlight, is radiated at no more than 6% of a maximum light intensity;
• a transmissive imager arranged in front of the backlight as seen in a viewing direction;
• at least one plate-shaped light guide located in front of the backlight as seen in the viewing direction, comprising a thermoplastic or thermoelastic material and scattering particles distributed therein, or having outcoupling elements on at least one of its faces;
• and
• light sources being arranged laterally at edges of the light guide;
• wherein, when scattering particles are provided in the light guide, the scattering particles comprise titanium dioxide, barium sulfate, silsesquioxane particles and/or cross-linked polystyrene particles of a mean particle size of 150 to 500 nm, which are used in a concentration of 0.01 to 300 wt.-ppm related to the weight of the light guide, and wherein the light guide has nothing printed on it and no light-scattering imperfections;
• and wherein
• the light guide is transparent to at least 85% of the light originating from the backlight;
• so that, in the free-viewing mode, light laterally incident from the light sources into the light guide in directions located within angles between 45 degrees and 75 degrees relative to the surface normal of the backlight are radiated at no less than 12% of the maximum light intensity of light radiated from the light guide normal to the surface;
• and so that the light originating from the light sources, if they are switched on, and exiting the light guide from at least one point of its surface, has, in at least one angle α relative to the surface of the light guide, with α<80 degrees, a higher light intensity than the light exiting from the said point of the surface of the light guide normal to that surface;
• wherein, in the restricted-viewing mode, the backlight is switched on, and the light sources are switched off, and wherein, in the free-viewing mode, at least the light sources are switched on.