Composite pane for a head-up display with an electrically conductive coating and an anti-reflective coating

1 . A composite pane for a head-up display (HUD) with an upper edge, a lower edge, and an HUD region, comprising an outer pane and an inner pane, which are joined to one another by a thermoplastic intermediate layer, and a transparent, electrically conductive coating on a surface of the inner pane facing the intermediate layer or within the intermediate layer,

wherein the intermediate layer is formed by at least one ply of thermoplastic material, which is arranged between the electrically conductive coating and the outer pane,

wherein a thickness of the ply of thermoplastic material is variable with a wedge angle over its vertical course between the lower edge and the upper edge at least in the HUD region,

wherein an anti-reflective coating is applied on the surface of the inner pane facing away from the intermediate layer, and

wherein the wedge angle is selected so that the reflections at the electrically conductive coating and the reflections at the exterior-side surface of the outer pane are superimposed or for at least reducing the distance between said reflections at the electrically conductive coating and at the exterior-side surface of the outer pane such that a layer ghost image formed by the reflections at the electrically conductive coating is suppressed or reduced.

2 . The composite pane according to claim 1 , wherein the electrically conductive coating includes at least two electrically conductive layers, which are arranged between two dielectric layers or layer sequences.

3 . The composite pane according to claim 1 , wherein the anti-reflective coating is formed from alternatingly arranged layers with different refractive indices.

4 . A projection arrangement for a head-up display, at least comprising

a composite pane according to claim 1 , and

a projector that is aimed at the HUD region.

5 . The projection arrangement according to claim 4 , wherein the light of the projector has at least one p-polarised component, and

wherein the composite pane has, in the spectral range from 400 nm to 650 nm, only a single local reflection maximum for p-polarised light, which is in the range from 510 nm to 550 nm.

6 . The projection arrangement according to claim 5 , wherein, in the spectral range from 400 nm to 650 nm, the difference between the reflectance of a local reflection maximum and a minimally occurring reflectance for p-polarised light is at most 10%.

7 . The projection arrangement according to claim 5 , wherein the reflectance for s-polarised light in the spectral range from 450 nm to 600 nm is substantially constant such that a difference between the maximally occurring reflectance and a mean as well as a difference between a minimally occurring reflectance and the mean are at most 5%.

8 . The projection arrangement according to claim 4 , wherein the proportion of p-polarised light in the total light of the projector is from 20% to 80%.

9 . The projection arrangement according to claim 4 , wherein the electrically conductive coating includes at least four electrically conductive layers, which are in each case arranged between two dielectric layers or layer sequences.

10 . The projection arrangement according to claim 9 , wherein the electrically conductive layers are based on silver and have, in each case, a layer thickness from 5 to 15 nm, wherein a total layer thickness of all electrically conductive layers is from 20 nm to 50 nm.

11 . The projection arrangement according to claim 9 , wherein each dielectric layer sequence includes an anti-reflective layer, and wherein

the anti-reflective layer below the first electrically conductive layer has a thickness from 15 nm to 25 nm,

the anti-reflective layer between the first and the second electrically conductive layer has a thickness from 25 to 35 nm,

the anti-reflective layer between the second and the third electrically conductive layer has a thickness from 45 nm to 55 nm,

the anti-reflective layer between the third and the fourth electrically conductive layer has a thickness from 15 nm to 25 nm, and

the anti-reflective layer above the fourth electrically conductive layer has a thickness from 8 nm to 18 nm.

12 . The projection arrangement according to claim 9 , wherein all anti-reflective layers that are arranged between two electrically conductive layers are divided into a dielectric layer having a refractive index smaller than 2.1, and an optically high refractive layer having a refractive index greater than or equal to 2.1.

13 . The projection arrangement according to claim 4 , wherein the anti-reflective coating includes the following layers, starting from the inner pane:

a high refractive layer based on silicon nitride with a thickness from 15 nm to 25 nm,

a low refractive layer based on silicon dioxide with a thickness from 15 nm to 25 nm,

a high refractive layer based on silicon nitride with a thickness from 90 nm to 110 nm,

a low refractive layer based on silicon dioxide with a thickness from 80 nm to 100 nm.

14 . A method comprising utilizing a composite pane according to claim 1 in a motor vehicle as a windshield that serves as a projection surface of a head-up display.

15 . The composite pane according to claim 2 , wherein the electrically conductive coating includes at least four electrically conductive layers, which are in each case arranged between two dielectric layers or layer sequences.

16 . The projection arrangement according to claim 6 , wherein the difference between the reflectance of the local reflection maximum and the minimally occurring reflectance for p-polarised light is at most 8%.

17 . The projection arrangement according to claim 7 , wherein the difference between the maximally occurring reflectance and the mean as well as the difference between the minimally occurring reflectance and the mean are at most 1%.

18 . The projection arrangement according to claim 8 , wherein the proportion of p-polarised light in the total light of the projector is from 50% to 80%.

19 . The projection arrangement according to claim 12 , wherein the dielectric layer is based on silicon nitride, and the optically high refractive layer is based on a mixed silicon/metal nitride.