| CPC G02F 1/1323 (2013.01) [B60K 35/22 (2024.01); G02B 6/0036 (2013.01); G02F 1/133524 (2013.01)] | 12 Claims |
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1. A display screen which can be operated in at least two operating modes, B1 for an unrestricted viewing mode and B2 for a restricted viewing mode, comprising:
a transmissive image rendering device which modulates light that is incident upon it for displaying an image content and which can be operated in at least the first operating mode B1 for an unrestricted viewing mode and in the second operating mode B2 for a restricted viewing mode, wherein the transmissive image rendering device comprises an LCD panel with two liquid crystal layers, one of which serves to modulate the light in order to enable display of the image content, and the other serves to switch to a large viewing angle range in the first operating mode B1 for an unrestricted viewing mode and to limit the viewing angle range in the second operating mode B2 for a restricted viewing mode,
an illumination device which is located behind the transmissive image rendering device in a viewing direction of an observer and which can be operated in at least the two operating modes, B1 for an unrestricted viewing mode and B2 for a restricted viewing mode, wherein the illumination device emits light in an unrestricted viewing angle range in the first operating mode B1 and emits light in a limited viewing angle range in the second operating mode B2,
wherein the respective viewing angle ranges of the transmissive image rendering device and of the illumination device for operating mode B2 strongly overlap or are identical,
wherein the illumination device comprises at least:
i. a two-dimensionally extensive backlight which emits light in a limited angular range,
ii. a plate-shaped light guide which is situated in front of the backlight in the viewing direction and which has outcoupling elements on at least one of the large surfaces and/or within its volume, wherein the light guide is transparent to at least 50% of the light emanating from the backlight,
iii. illuminants arranged laterally at narrow sides of the light guide,
wherein the backlight is switched on and the illuminants are switched off in operating mode B2, wherein, further, at least the illuminants are switched on in operating mode B1, and wherein the outcoupling elements are selected with respect to their shape, quantity per surface area and extent in such a way that:
i. every outcoupling element is smaller with respect to its horizontal and vertical dimensions than the minimum of width and height of smallest pixels of the transmissive image rendering device, and that
ii. portions of, or the entire surface of, at least two outcoupling elements in each instance are arranged below each of the smallest pixels of the transmissive image rendering device in projection directions parallel to the surface normal of the light guide,
and
a control for the transmissive image rendering device and the illumination device for switching between the at least two operating modes B1 and B2; and
wherein at least one optical component is arranged between the image rendering device and the light guide, and wherein the at least one optical component is a diffuser and/or a prism film.
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