Low glare rear-view mirror for vehicles
A low-glare motor-vehicle includes a color reproduction index R a of at least 70 and a reduced reflection for each of the illuminants A and C in scotopic vision (at night) as compared with photopic vision (in the daylight) by at least 3%. In one embodiment, the mirror consists of a transparent substrate, a thin transparent metallic layer, an adapted dielectric layer and the reflector properly speaking.
1. A low-glare rearview mirror with non-variable optical properties for a vehicle, comprising:
a transparent layer carrier; and
a multi-layer coating of at least one dielectric and one metallic material;
wherein a ratio between scotopic reflection values for CIE-designated illuminants A and C and photopic reflection values for the CIE-designated illuminants A and C is maximally 97% and wherein a color reproduction index R a according to DIN EN 410 is at least 70.
2. The rearview mirror as recited in claim 1 , wherein the ratio between the reflection values is maximally 80%.
3. The rearview mirror as recited in claim 1 , wherein the color reproduction index R a according to DIN EN 410 is at least 75.
4. The rearview mirror as recited in claim 1 , wherein the transparent layer carrier includes soda-lime glass.
5. The rearview mirror as recited in claim 1 , wherein the coating is disposed on a side of the layer carrier facing away from a viewer and includes at least the following layers, in the order of their deposition:
a) a transparent metallic layer;
b) a dielectric layer; and
c) a metallic reflecting layer.
6. The rearview mirror as recited in claim 5 , wherein the transparent metallic layer includes NiCr and has a thickness of 1 to 21 nm.
7. The rearview mirror as recited in claim 5 , wherein the dielectric layer includes TiO 2 , SiO 2 or SnO 2 .
8. The rearview mirror as recited in claim 5 , wherein an optical thickness do of the dielectric layer relates to a function of its refractive index n530 with a wavelength of 530 nm as follows:
for a refractive index n530 of maximally 1.99, the optical thickness do is at least the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.46, do=235 nm) and (n530=1.99, do=216 nm), and maximally the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.46, do=362 nm) and (n530=1.99, do=353 nm), and
for a refractive index n530 of at least 1.99, the optical thickness do is at least the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.99, do=216 nm) and (n530=2.48, do=205 nm), and maximally the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.99, do=353 nm) and (n530=2.48, do=340 nm).
9. The rearview mirror as recited in claim 8 , wherein the optical thickness do of the dielectric layer is:
for a refractive index n530 of maximally 1.99, the optical thickness do is at least the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.46, do=244 nm) and (n530=1.99, do=233 nm), and maximally the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.46, do=335 nm) and (n530=1.99, do=330 nm), and
for a refractive index n530 of at least 1.99, the optical thickness do is at least the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.99, do=233 nm) and (n530=2.48, do=225 nm), and maximally the value specified through the straight line given in the (n530, do) space and running through the points (n530=1.99, do=330 nm) and (n530=2.48, do=319 nm).
10. The rearview mirror as recited in claim 5 , further comprising an additional dielectric layer disposed between the reflecting layer and the dielectric layer.
11. The rearview mirror as recited in claim 10 , wherein the additional dielectric layer has a lower refractive index than the dielectric layer.
12. The rearview mirror as recited in claim 10 , wherein the additional dielectric layer includes at least one of SiO 2 , MgF 2 and SnO 2 .
13. The rearview mirror as recited in claim 10 , wherein a sum of the optical-layer thicknesses of the dielectric layer and the additional layer is at least 250 nm, and maximally 390 nm.
14. The rearview mirror as recited in claim 11 , wherein the sum of the optical-layer thicknesses of the dielectric layer and the additional layer is at least 275 nm, and maximally 375 nm.
15. The rearview mirror as recited in claim 10 , wherein a sum of the optical-layer thicknesses of the dielectric layer and the additional layer is at least 530 nm, and maximally 670 nm.
16. The rearview mirror as recited in claim 15 , wherein the sum of the optical-layer thicknesses of the dielectric layer and the additional layer is at least 560 nm and maximally 635 nm.
17. The rearview mirror as recited in claim 10 , wherein the reflecting layer includes at least one of Al, Ni, Ti, Cr and of an alloy of these materials.
18. The rearview mirror as recited in claim 17 , wherein the reflecting layer includes Cr.
19. The rearview mirror as recited in claim 10 , further comprising at least one of a hydrophilic and/or photocatalytically active coating disposed on a front side of the layer carrier.