two light source modules, arranged in such a way that at least parts of projections overlap, wherein each of the light source modules comprises:

a turning film; and

a light guide plate (LGP), arranged parallelly under the turning film and having a light emergent surface facing the turning film and a light incident side at a side of the light emergent surface, wherein a light-emitting element arranged on the light incident side emits a light ray, the light ray enters the LGP from the light incident side and exits the LGP from the light emergent surface, with more than 85% of light energy being concentrated between 70° and 90° with respect to a normal direction of the light emergent surface, then enters the turning film and is steered right, and exits the turning film from a surface of the turning film away from the LGP, with more than 80% of the light energy being concentrated between −30° and +30° with respect to left and right viewing angles relative to the normal direction of the light emergent surface, and the light incident side of the LGP of one of the light source modules is perpendicular to the light incident side of the LGP of the other light source module, wherein

the switchable backlight module is in an anti-peeping mode having a narrow viewing angle when only an upper one of the light source modules emits light and the switchable backlight module is in a non-anti-peeping mode having a wide viewing angle when both of the two light source modules emit light, wherein the viewing angle of the light ray emitted by the upper one of the light source modules is more narrow than the viewing angle of the light ray emitted by the lower one of the light source modules;

wherein a plurality of prism strips extending in a direction parallel to the light incident side of the LGP are arranged on a surface of the turning film;

wherein the prism strips of the turning film of one of the light source modules are perpendicular to the prism strips of the turning film of the other of the light source modules;

wherein more than 50% of the light energy after the light ray is steered right is concentrated between −10° and +10° with respect to the left and right viewing angles relative to the normal direction of the light emergent surface.