PROJECTION ASSEMBLY FOR A HEAD-UP DISPLAY (HUD) WITH P-POLARIZED RADIATION
A projection assembly for a head-up display (HUD), includes a composite pane, including an outer pane and an inner pane that are joined to one another via a thermoplastic intermediate layer, the composite pane having an HUD region; an HUD reflection layer suitable for reflecting p-polarized radiation, on the surface of the outer pane or of the inner pane facing the intermediate layer or within the intermediate layer; an HUD projector that is directed at the HUD region and that emits p-polarized radiation; and a high-refractive-index coating having a refractive index of at least 1.7 on the surface of the inner pane facing away from the intermediate layer. The high-refractive-index coating is a sol-gel coating.
1 . Projection A projection assembly for a head-up display, comprising:
a composite pane, comprising an outer pane and an inner pane that are joined to one another via a thermoplastic intermediate layer, the composite pane having an HUD region;
an HUD reflection layer suitable for reflecting p-polarized radiation, on a surface of the outer pane or of the inner pane facing the thermoplastic intermediate layer or within the thermoplastic intermediate layer;
an HUD projector that is directed at the HUD region and that is adapted to emit p-polarized radiation, and
a high-refractive-index coating having a refractive index of at least 1.7 on a surface of the inner pane facing away from the thermoplastic intermediate layer,
wherein the high-refractive-index coating is a sol-gel coating.
2 . The projection assembly according to claim 1 , wherein the radiation of the HUD projector strikes the composite pane with an angle of incidence of 58° to 72°.
3 . The projection assembly according to claim 1 , wherein the refractive index of the high-refractive-index coating is at least 1.8.
4 . The projection assembly according to claim 1 , wherein the high-refractive-index coating contains silicon nitride, a mixed silicon-metal nitride, aluminum nitride, tin oxide, manganese oxide, tungsten oxide, niobium oxide, bismuth oxide, titanium oxide, mixed tin-zinc oxide, zirconium oxide, scandium oxide, yttrium oxide, tantalum oxide, lanthanum oxide, or cerium oxide.
5 . The projection assembly according to claim 1 , wherein a thickness of the high-refractive-index coating is at most 100 nm.
6 . The projection assembly according to claim 1 , wherein the high-refractive-index coating contains titanium oxide or zirconium oxide.
7 . The projection assembly according to claim 1 , wherein a reflection quotient R 20 /R IV is at least 50:1, wherein R 20 is the reflectance of the HUD reflection layer and R IV is the reflectance of the surface provided with the high-refractive-index coating, in each case with respect to p-polarized radiation.
8 . The projection assembly according to claim 1 , wherein the high-refractive-index coating is not applied over the entire surface of the inner pane, but at least on a region of the surface that contains the HUD region.
9 . The projection assembly according to claim 1 , wherein the refractive index of the high-refractive-index coating has a gradient, wherein the refractive index decreases in a direction from a lower edge to an upper edge of the composite pane.
10 . The projection assembly according to claim 1 , wherein the HUD reflection layer is an HUD reflection coating that is implemented as a thin-film stack that includes at least one electrically conductive layer.
11 . The projection assembly according to claim 1 , wherein the HUD reflection layer is an HUD reflection coating that is implemented as a thin-film stack that contains only dielectric layers.
12 . The projection assembly according to claim 1 , wherein the HUD reflection layer is a polymer film that includes a plurality of polymeric plies, wherein plies with a higher and a lower refractive index are arranged alternatingly.
13 . The projection assembly according to claim 1 , wherein the composite pane is equipped with a further high-refractive-index coating on the surface of the outer pane facing away from the thermoplastic intermediate layer.
14 . The projection assembly according to claim 1 , wherein the outer pane and the inner pane are made of soda lime glass.
15 . The projection assembly according to claim 1 , wherein the composite pane is a windshield of a passenger car.
16 . The projection assembly according to claim 2 , wherein the angle of incidence is from 62° to 68°.
17 . The projection assembly according to claim 3 , wherein the refractive index of the high-refractive-index coating is at least 2.0.
18 . The projection assembly according to claim 5 , wherein the thickness of the high-refractive-index coating is at most 50 nm.
19 . The projection assembly according to claim 18 , wherein the thickness of the high-refractive-index coating is at most 10 nm.
20 . The projection assembly according to claim 10 , wherein the at least one electrically conductive layer is based on silver.