WO2018167126A1 - Antireflection coating - Google Patents

Abstract

The aim of the invention is to provide an antireflection system that is as robust as possible in terms of optical properties on uneven surfaces. To this end, a transparent element (1) is provided, comprising: a transparent substrate (3); and on said substrate (1), a multilayer antireflection coating (5) comprising at least six layers, in which layers having a high refractive index (51, 53, 55) alternate with layers (50, 52, 54, 56) having a low refractive index; and the layers (51, 53, 55) having a high refractive index are harder than the layers (50, 52, 54, 56) having a low refractive index, the uppermost layer (56, 60) of the multilayer antireflection coating (5) being a layer having a low refractive index; the substrate comprising at least two surface areas (30, 32) that differ in terms of the incline thereof; and the antireflection coating (5) covering the surface areas (30, 32) having a different incline. For the antireflection coating (5) on the surface areas (30, 32), at least one of the following features is valid: the colours of the remaining reflection respectively below a 0° angle of incidence on the surface areas (30, 32) differ from each other in the CIE xyz-colour system by no more than ∆x=0.05, ∆y=0.05, preferably no more than ∆x=0.03, ∆y=0.03, and particularly preferably no more than ∆x=0.02, ∆y=0.02; and the photopic reflectivities below a 0° angle of incidence of the surface areas (30, 32) differ from each other by no more than ∆R_ph=1.5%.

Description

 Anti-reflection coating

description

Antireflecting layer systems are state of the art today and are used in a variety of ways. Fields of application include image glazing, optical components such as lenses e.g. for cameras. These applications are not exposed to heavy mechanical stress.

 EP 2 492 251 B1 describes the production of anti-reflective

Layer systems for u.a. the watch glass industry. In addition to the antireflection effect, the hardness of the AR system is thereby improved by using a high-index layer

Hard material layer of S13N4 is introduced with an admixture of aluminum. Since watches and in particular so-called loupes for the date display, which are glued to the glass, are often mechanically stressed by scratching, the use of conventional anti-reflective layer systems is not useful, since they can be completely removed due to mechanical stress and the reflection of the substrate material is formed. The hard AR system based on the development according to EP 2 492 251 B1 provides an antireflection system which is mechanically much more durable than conventional optical coatings.

 Since sapphire is frequently used as a watch glass in the watch industry, but antireflection coatings are generally much softer than sapphire, it would be desirable to be able to obtain the antireflection effect as well as possible despite mechanical stress, ie. that the residual reflection remains as low as possible even after mechanical stress. This is achieved according to EP 2 492 251 B1 by the hard material layers, which have a high

 Abrasion resistance of the layer system and thus cause only a small change in the layer thicknesses.

Among the layers of hard material, two-component systems traditionally play the main role. Here are mainly the oxides and nitrides of Cr, Si, Ti and Zr to call. These are mainly used in the coating of tools, so they do not have to be transparent for this application. Known transparent hard material layers are, for example, Al 2 O 3, as in the DE 20106167, and yttrium-stabilized Zr0 ₂ . In EP 1 453 770 B1

Described glass-ceramic substrates which are coated with carbon-doped silicon nitride.

 WO 2009/010180 A1 and DE 10 2008 054 139 A1 describe aluminum-doped SiN or SiON layers having scratch-resistant action as individual layers.

 DE 10 2016 125 689 A1 and DE 10 2014 104 798 A1 describe AR systems with a modified composition of the high-index layer, wherein the layers according to DE 10 2016 125 689 A1 are amorphous, while the layers according to FIG

DE 10 2014 104 798 A1 contain nano-crystallites.

 Typically, scratch-resistant antireflective coatings are deposited by sputtering. In this case, the antireflection coatings described in the prior art are designed for flat documents. If the surface is not flat, the angle of the surface normal to the sputtering source changes locally. This leads to a directional

Thickness variation of the individual layers. This changes the optical properties.

 The aim of the invention is therefore to provide an antireflection system which can be deposited on non-planar substrates and still has good optical properties. Preferably, the layer system is as insensitive as possible to a partial abrasion of the uppermost layer. The abrasion can be done with an abrasion test, z. B. the modified Bayer test, based on ASTM F735-11, but preferably with 2 kg of corundum sand and 8000 cycles are tested. This modified Bayer test is also described in the abovementioned publications DE 10 2016 125 689 A1 and DE 10 2014 104 798 A1, the disclosure of which is also made the subject of the present application in this regard. By such a test of the top (last) layer of

Antireflective coating typically removes more than ten nanometers of material. This amount of material also corresponds to more than ten percent of the typical layer thicknesses

Layer thickness. Experiments have shown that the modified Bayer test applied to in EP 1 453 770 B1, DE 10 2014 104 798 A1 and DE 10 2016 125 689 A1

Coatings causes such material removal at the topmost layer. For example, the average layer thickness can be reduced by the Bayer test from 100 nm to 80 nm. Many scratches occur, but if the reflectance spectrum is measured over a large area (eg on an area of 5x5 mm ² ), the abraded coating can be given a macroscopic resulting reflectivity or a macroscopic resultant

Assign residual reflection color that corresponds to the visual impression. To the change of the residual reflection as insensitive as possible to the

To make vapor deposition, the invention is based on the idea to compare or select layer sequences with each other in the design of the layer system that the smallest possible change in optical parameters in terms of color of the residual reflection, their angular dependence and especially the intensity of the residual reflection, if the layer thicknesses the positions are changed by the same percentage.

 In particular, the invention provides a transparent element comprising

 a transparent substrate and on this substrate

 a multilayer antireflective coating comprising at least six layers, wherein high refractive index layers alternate with lower refractive index layers, and wherein

 the higher refractive index layers have greater hardness than the lower refractive index layers, and wherein the uppermost layer of the multilayer antireflective coating is a lower refractive index layer, and wherein

- The substrate has at least two surface areas which differ in their inclination, wherein

 the antireflection coating covers the surface areas of different inclination, and wherein for the antireflection coating on the surface areas at least one of the following features applies:

- The colors of the residual reflection at 0 ° angle of incidence on the surface areas differ in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, preferably not more than Δχ = 0.03, Ay = 0.03, more preferably not more as Δχ = 0.02, Ay = 0.02,

 - The photopic reflectivities at 0 ° angle of incidence of the surface areas do not differ from each other by more than AR_ph = 1.5%.

 The difference is to be understood in terms of amount. The terms "higher refractive index" and "lower refractive index" are to be understood as a comparison relative to each other. Thus, a layer with a higher refractive index is understood to be a layer whose refractive index is higher than a layer having a lower refractive index, without the quantification of the absolute values of the refractive indices.

As a photopic reflectivity, the integrated reflectivity is referred to, after this with the sensitivity curve of the human eye with sufficient brightness (daytime vision) was weighted. For the information given herein, the standard light source D65 was used as the light source according to ISO standard 3664, a radiation distribution with a color temperature of 6504 Kelvin.

 In particular, due to the more or less directed deposition process, the layer thickness of the antireflection coating depends on the inclination of the various

Surface areas vary. The layer system is then designed so that this is as little as possible dependent on a uniform reduction of the layer thicknesses of the individual layers with respect to the reflectivity and the color of the residual reflection. In particular, the antireflection coating may be designed such that at least one of the following features applies: with reduced layer thicknesses by a factor k which is smaller than 0.9, the color of the residual reflection differs from the light incidence angle arccos (k) Color below 0 ° light incidence angle at unchanged layer thicknesses of the layers (50-56) in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, preferably not more than Δχ = 0.03, Ay = 0.03, more preferably not more than Δχ = 0.02, Ay = 0.02,

with reduced layer thicknesses by a factor k which is smaller than 0.9, the color of the residual reflection under an angle of incidence arccos (k) differs from the color below 0 °

Incidence angle for unaltered layer thicknesses of the layers (50 - 56) by no more than AR_ph = 1 .5%. Since the reduction in layer thicknesses is caused by the slope of the respective surface, these two quantities are substantially proportional and can be used equivalently.

According to a preferred embodiment of the invention, the substrate has a flat central area and a chamfer, or more generally an edge area, wherein the antireflection coating covers both the center area and the chamfer or edge area, wherein the layer thicknesses of the layers of the antireflection coating on the Be reduced chamfer or the edge region with respect to the layer thicknesses in the center region. In particular, this reduction can be uniform in that all layers are reduced in thickness by the same percentage. Such a configuration results when the antireflective coating is made by a directional coating process with the center region aligned with the coating source. The inventive design of the antireflection coating then results in no or at least no significant deviation of the color of the residual reflection or the reflectivity on the chamfer, or at the edge region. According to one embodiment of the invention can be between the surface normal of Bevel or edge region and the surface normal of the center region an angle of at least 20 ° are included. In particular, it is also intended for chamfers with an angle of 30 ° to 80 ° including cases of chamfered at 45 ° and 60 ° chamfers.

In general, it is favorable if, for a given inclination of a surface area, that is to say for example the angle of a chamfer, the antireflection coating is also optimized for this angle with respect to the color of the residual reflection and / or the photopic reflectivity. If, for example, a chamfer with a specific angle (for example 45 °) to a flat central surface is provided, the layer system can be optimized such that the difference of the color values Δχ, Δν is minimal or at least equal for an equally large angle of incidence of light (ie also 45 °) is less than 0.05, preferably less than 0.03.

 The middle area can z. B. color neutral. If a design were to be limited to the middle area only and leave the effect on the chamfer to chance, the chamfer could, for example, be coated after coating. B. have an orange residual reflection color. Now, in another embodiment, the design color of center region and edge region (eg, the chamfer) may differ and the center region z. B. color neutral and the chamfer be performed bluish.

 Preferably, the layers of the antireflective coating are given

In terms of their thickness refractive indices continue to be chosen so that

 - The color of the residual reflection at an angle of incidence of between 30 ° -arccos (0.9) = 4 ° and 30 ° + arccos (0.9) = 56 °, at 10% reduced layer thicknesses of the color below 30 °

Angle of incidence at unreduced layer thicknesses in the CIE xyz color system does not differ by more than Δχ = 0.05, Ay = 0.05, and / or

 - The color of the residual reflection at an angle of incidence of between 45 ° -arccos (0.9) = 19 ° and 45 ° + arccos (0.9) = 71 °, at 10% reduced layer thicknesses of the color at 45 ° incidence angle at undiminished layer thicknesses in the CIE xyz color system does not differ by more than Δχ = 0.05, Ay = 0.05.

 The antireflective coating may also be designed so that the color of the residual reflection at 0 ° incidence angle is evenly reduced by at least 10%

Layer thicknesses of all layers differ from the color below 0 ° light angle of incidence (viewing angle with respect to the surface in the corresponding surface area) with undiminished layer thickness of the uppermost layer in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, in particular by no more than Δχ = 0.03, Δν = 0.03, preferably not more than Δχ = 0.02, Δν = 0.02 differs.

 Furthermore, the two features mentioned above Δχ = 0.05, Δν = 0.05 and / or a change in photopic reflectivity by at most AR_ph = 1.5% according to an embodiment of the invention even with significantly greater reduction of the layer thicknesses of all layers, namely by 20%, or 30 %, or even 40%.

 Such a reduction of all layer thicknesses continuously and up to a certain angular range z. B. in lenses and domes, or arched windows. However, it is very difficult to have very good optical properties over a larger coating angle

To get properties. In many cases, it is therefore beneficial to focus on the

 To limit coating angles in the design that actually occur. For a flat component with 45 ° bevel, the design z. B. be limited to the two coating angles 0 ° and 45 °, while the viewing angle over the entire range of 0 ° to 45 ° should be included in the design.

 The reduction of all layer thicknesses is due to the fact that when inclined

Surfaces during the coating in the same time on the same cross-section the same amount of material is deposited. However, since the corresponding area of the area to be coated is now arranged at an angle (eg a chamfer of 45 °), the actual area is larger and consequently the layer thickness is smaller. With perfect collimated / directional coating, the layer thickness would be reduced by a factor of the cosine of the tilt angle. Below 0 °, as usual, 100% relative layer thickness is deposited. But at 45 ° it would only be 71%. In typical sputtering processes, however, coatings do not run off in a completely directed manner, but the deposition takes place from a kind of cloud, so that the layer thicknesses are typically somewhat larger. The following table shows measured

Layer thickness changes for a nitride layer in magnetron sputtering at different angles of the coated surface to the sputtering source, as well as changes in the

Refractive index:

 Layer thickness changes due to coating tilt angles

 Coating angle 0 ° 45 ° 60 °

 Cos (coating angle) 100% 70.7% 50%

Measured Relative Layer Thickness 100% 72% 55% Relative Refractive Index at 550 nm 100% 100.14% 101.07% If appropriate, the layer system according to the invention can be further optimized in such a way that not only is the insensitivity of the optical properties to one

uniform change in the layer thickness of all layers, but also a change in the layer thickness of only the uppermost layer occurs. Such an effect occurs when the coating wears off over time. For this purpose, according to a development of the invention, a transparent element is provided comprising a transparent substrate and on this substrate a multilayer antireflection coating according to the invention, wherein the layers are selected with respect to their refractive indices in terms of thickness, that with a reduction of the layer thickness of the uppermost layer by 10% or 10 nm, depending on which of these cases gives the lower remaining layer thickness, so that the layer thickness after the

Reduction in the first case is still 0.9 times the original layer thickness, and at the same layer thickness of the remaining layers at least one of the following features applies:

 - The color of the residual reflection at 0 ° angle of incidence with a reduced layer thickness differs from the color below 0 ° light incidence angle with undiminished layer thickness of the uppermost

Position (54) in the CIE xyz color system by no more than Δχ = 0.05, Δν = 0.05,

 - The photopic reflectivity at 0 ° angle of incidence with a reduced layer thickness differs from the photopic reflectivity at 0 ° incidence angle with undiminished layer thickness by not more than AR_ph = 1.5%.

 The case of a reduction of the layer thickness by 10 nm results at layer thicknesses of the uppermost layer of less than 100 nm.

 According to a development, the layer system is further designed so that in the

Reduction of the layer thickness of all layers by 10% the photopic reflectivity below 0 °

Angle of incidence by no more than AR_ph = 1%, more preferably not more than

 AR_ph = 0.5%, very particularly preferably not more than AR_ph = 0.25% deviates from the value at undiminished layer thicknesses.

 According to yet another embodiment of the invention, the layers are given

 Refractive indices selected in terms of their thickness so that the color of the residual reflection at 45 ° angle of incidence at 10% reduced layer thicknesses of all layers of the color below

45 ° angle of incidence with undiminished layer thickness in the CIE xyz color system by no more than Δχ = 0.05, Δν = 0.05, preferably Δχ = 0.03, Ay = 0.03, more preferably Δχ = 0.02, Ay = 0.02 differs.

 In addition, the layer system can also be further tuned to the effect that at least in one area of the surface the transparent element has at least one of the following features, preferably also several, in particular also all features:

- the color of the residual reflection on the antireflective coating at 30 ° angle of incidence differs from the color at 0 ° angle of incidence in the CIE xyz color system by no more than Δχ = 0.02, Ay = 0.02,

 - the color of the residual reflection at 45 ° angle of incidence differs from the color at 0 ° angle of incidence by not more than Δχ = 0.05, Ay = 0.05,

 - the photopic reflectivity at 0 ° angle of incidence is less than 1, 5%, preferably less than 1%, in particular less than 0.8%

the maximum of the reflectivity in the wavelength range between 450 nm and 700 nm under 0 ^C angle of incidence is less than 1.5%,

the absolute value of the difference of the photopic reflectivity at 30 ° incidence angle to the photopic reflectivity at 0 ° incidence angle is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%,

 the absolute value of the difference of the photopic reflectivity at an angle of incidence of 45 ° to the photopic reflectivity at an angle of incidence of 0 ° is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%,

 the average reflectivity, averaged in the wavelength range between 450 nm and 700 nm at 0 ° angle of incidence, is less than 1.5%, preferably less than 1.0%,

 the absolute value of the difference of the average reflectivities below 30 ° incidence angle and below 0 ° incidence angle, averaged in the wavelength range between 450 nm and 700 nm, is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1 %

the absolute value of the difference between the average reflectivities at 45 ° incidence and at 0 ° incidence, averaged over the wavelength range between 450 nm and 700 nm, is less than 0,5%

 the absolute value of the difference between the maxima of the reflectivities in the wavelength range between 450 nm and 700 nm at 30 ° incidence angle and at 0 ° incidence angle is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%,

- The absolute amount of the difference of the maxima of the reflectivities in the wavelength range between 450 nm and 700 nm at 45 ° incidence angle and at 0 ° incidence angle is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%.

 The average reflectivity is the average value of the reflectivity in the wavelength range from 450 to 700 nm.

 In a development of this embodiment, the coating can even fulfill at least one of the following features:

 the photopic reflectivity at 0 ° angle of incidence is less than 1%, preferably less than 0.8%,

 the absolute value of the difference of the photopic reflectivity at 30 ° incidence angle to the photopic reflectivity at 0 ° incidence angle is less than 0.1%,

 the absolute value of the difference of the average reflectivity in

Wavelength range between 450 nm and 700 nm at 30 ° incidence angle

average reflectivity in the wavelength range between 450 nm and 700 nm at 0 ° angle of incidence is less than 0.1%,

 the absolute value of the difference of the photopic reflectivity at an angle of incidence of 45 ° to the photopic reflectivity below 0 ° incidence angle is less than 0.2%,

 the absolute value of the difference of the average reflectivity in

Wavelength range between 450 nm and 700 nm at 45 ° incidence angle

average reflectivity in the wavelength range between 450 nm and 700 nm at 0 ° angle of incidence is absolutely less than 0.2%,

 - the average reflectivity, averaged in the wavelength range between 450 nm and 700 nm at 0 ° angle of incidence is less than 1, 0%.

 According to a further development of the invention, the layer system is designed so that visually differ as little as possible under a given angle to the transparent element, the surfaces with the different inclinations. Accordingly, at least one further area of the surface should be present, which is arranged at an angle to the previously described area with the properties described above (eg a chamfer or curvature) and on which all layers with a different thickness are deposited during the coating process and at least one of the following features, preferably also several, in particular all features:

the color of the residual reflection at 0 ° angle of incidence on the first area (main area described above) differs from the color on a wider area (eg. Chamfer) under likewise respective 0 ° light incidence angle on this area in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05,

 - the color of the residual reflection at 0 ° angle of incidence on the first area

differs from the color on a wider range when light incidence from the identical direction of incidence (angle of incidence is in the case of the inclination angle of the two

 Surface areas to each other) in the CIE xyz color system by no more than Δχ = 0.05, Ay = 0.05,

- the color of the residual reflection at 0 ° angle of incidence on the first area

differs from the color on a further range under all light incidence angles between 0 ° and the angle of inclination of the two surface areas to each other in the CIE xyz color system by no more than Δχ = 0.05, Ay = 0.05,

 - The color of the residual reflection at an angle of incidence between 0 ° and the

The angle of inclination of the two surface areas relative to one another on the first area differs from the color on a wider area under incident light from the identical direction in the CIE xyz color system by no more than Δχ = 0.05, Ay = 0.05.

 To customize the design so-called targets can be defined. these are

Specifications of z. B. reflectivity spectrum, photopic (integrated) reflectivity, residual reflection color, etc. These targets can be defined for different angles and weighted in their importance or prioritization. Such targets can with values z. For example, as links such as "less than" or "as close as possible". Colors are defined as "as close as possible to" the desired color location, reflectivities as "less than" a desired limit. Furthermore, deviations can then be penalized and with these penalizations the layer thicknesses of the design can be optimized in such a way that the least possible penalization is achieved. With weights, deviations of different parameters can enter into the penalization with different degrees of intensity. So z. B. the

Residual reflection color or the reflectivity at 45 ° less important weight than below 0 °. The weights are adjusted in the process so that desired results of the coating characteristics are achieved.

 In particular, at least two, preferably a plurality of designs are defined, wherein the layer thicknesses and layer materials are selected such that they correspond to one another

Coating process on different surface areas different

Inclination angle correspond. Are z. B. a main area of a surface and arranged at angles other areas simultaneously coated normal to the main surface, wherein on the other areas, the layer thicknesses and, where appropriate, the refractive indices of the different layers are changed in comparison to the parameters for the main area, then the other layer designs should reflect just these changed coating conditions. Is z. B. a coating of 7 layers with two alternating

Materials where d1, d2, ... are the layer thicknesses on a first surface area and the L and H are the two materials (with low and high refractive indices L1 and H1) could be a coating design for a first area of a surface (B1)

describe as follows:

 B1: d1 [L1] d2 [H1] d3 [L1] d4 [H1] d5 [L1] d6 [H1] d7 [L1].

 [L1] denotes a layer with a low refractive index, [H1] a layer with a high refractive index, d1 - d7 the respective layer thicknesses of these layers.

 A design B2 with a different thickness and modified refractive indices of the layers can now be z. B. describe as follows

 B2: 0J1 * d1 [L2] 0.71 * d2 [H2] 0J1 * d3 [L2] 0.71 * d4 [H2] 0.71 * d5 [L2] 0.71 * d6 [H2]

0.71 * d7 [L2]. In the case of Design B2, all layers are therefore uniformly reduced by 29% in their thickness. In this example, the factor 0.71 approximates the cosine of 45 ° and it is assumed that the design refers to a surface area that is at 45 ° to the coating direction. The exact factor can be determined in preliminary tests since different coating processes and deposition systems can result in individual layer reductions. By certain 3-dimensional rotation systems of the substrate holder in

Coating machines, this factor can be increased to 1. The factors determined may also differ for a range of layer material to layer material.

 The different refractive indices of one layer material in each case relate to identical coating materials which, however, when deposited at different angles, also develop different refractive indices.

 More preferably, at least three, more preferably still more designs are defined, with at least two designs differing in all layer thicknesses (for

Simulation of the coating under angle, z. B. on a chamfer) and at least one further design only in the uppermost layer a reduced thickness learns that simulates a simulation of abrasion. If the layer thickness change of all layers deposited at an angle σ is now the same, one could express it with the factor w (the typically between cos (a) and 1), the three designs could now be described as follows:

 B1: d1 [L1] d2 [H1] d3 [L1] d4 [H1] d5 [L1] d6 [H1] d7 [L1]

 B2: w * d1 [L2] w * d2 [H2] w * d3 [L2] w * d4 [H2] w * d5 [L2] w * d6 [H2] w * d7 [L2]

 B3: d1 [L1] d2 [H1] d3 [L1] d4 [H1] d5 [L1] d6 [H1] 0.9 * d7 [L1]

 The method now comprises defining the targets for each of these designs and adapting all the designs simultaneously (by changing the layer thicknesses d1, d2,...), The designs still differing only by the same layer thickness differences. The targets for the different coating designs may differ and be weighted differently. So z. For example, the residual reflection color or the reflectivity for the design, where the last layer is reduced in thickness by 40 nm, will be weighted less important than for the design in which the last layer is not reduced in thickness.

 An automatic adjustment procedure which is subjected to this procedure generally generates several different solutions that are optimally optimally different or differently optimized with respect to different parameters. So z. B. a solution the

 Residual reflection paint with reduction of the thickness of the last layer keep more constant and another solution the more photopic reflectivity.

 The process according to the invention for producing a transparent element can be summarized as follows:

 it is for at least a pair of antireflection coatings (5, 6), which at least six layers (50, 51, 52, 53, 54, 55, 56), wherein high refractive index layers (51, 53, 55 ) alternate with lower refractive index layers (50, 52, 54, 56), the higher refractive index layers (51, 53, 55) having greater hardness than the lower refractive index layers (50, 52, 54, 56), and wherein the uppermost layer (56, 60) of the multilayer antireflective coating (5) is a lower refractive index layer, taking into account the refractive index of the substrate (3) of at least one of the parameters

- Color of the residual reflection and

 - Photopic reflectivity

calculated, wherein the two antireflection coatings differ with respect to the layer thicknesses of all layers, such that the layer thicknesses of all layers in an antireflection coating by a common factor, which has a value of at most 0.9,

or between 0 and 0.9, preferably in the range of 0.1 to 0.9, is reduced compared to the layer thickness of the other antireflection coating, and it is checked whether at least one of the conditions is fulfilled for both antireflection coatings:

- The color of the residual reflection at 0 ° angle of incidence evenly reduced

Layer thicknesses differ from the color below 0 ° light incidence angle with unreduced layer thicknesses in the CIE xyz color system by no more than Δχ = 0.05, Δν = 0.05,

 - The photopic reflectivity at 0 ° angle of incidence with uniformly reduced layer thickness of all layers (50, 51, 52, 53, 54, 55, 56) differs from the photopic reflectivity at 0 ° incidence angle at undiminished layer thicknesses by not more than AR_ph = 1. 5%

 with reduced layer thicknesses by a factor k, which is smaller than 0.9, the color of the residual reflection under a light incidence angle arccos (k) differs from the color below 0 °

Incidence angle for unreduced layer thicknesses of the layers (50-56) in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, preferably not more than Δχ = 0.03, Ay = 0.03, more preferably not more than Δχ = 0.02, Ay = 0:02,

 with reduced layer thicknesses by a factor k which is smaller than 0.9, the color of the residual reflection under an angle of incidence arccos (k) differs from the color below 0 °

 Light angle of incidence with unreduced layer thicknesses of the layers (50-56) by no more than AR_ph = 1 .5%, and wherein for at least one further pair of antireflective coatings (5, 6) the parameters of the color of the residual reflection and the photopic reflectivity are calculated and again, at least one of the conditions is checked when the condition is not met for the first pair, and wherein a layer sequence having unreduced layer thicknesses is selected from a pair of antireflective coatings meeting at least one of the conditions, and wherein an antireflective coating is deposited on a substrate with this selected layer sequence.

 According to one embodiment, the color of the residual reflection and the photopic reflectivity for vertical incidence of light, i. determined at 0 ° light incidence angle. Instead of just a pair of antireflective coatings (5, 6), a larger number of designs can also be brought into the simultaneous fitting process, e.g. For example, four designs where the second in the last layer thickness is reduced by 10% as just described, a third, with 20%

Layer thickness reduction and a fourth with 30% layer thickness reduction. In this way, a particularly good adaptation of the layer design can also be obtained on continuously curved surfaces. If one of the conditions is not met, according to the invention, at any rate, searches continue among the solutions found. Furthermore, it is typically necessary to optimize the weights and values of the targets so that customizing the designs generates solutions that meet or best meet the desired conditions. In particular, this search can also be continued if a suitable pair of antireflection coatings (5, 6) has already been found, either in order to fulfill further conditions already mentioned above, or also to find the best possible layer system , In general, in any case, a plurality of pairs can be checked for the above-mentioned conditions (namely, the difference of the color of the residual reflection at 0 ° angle of incidence and / or the difference of the photopic reflectivity at 0 ° angle of incidence) and among the examined pairs the layer system for the Deposition are selected in which the smallest difference of the color of the residual reflection below 0 °

Light incident angle and / or the smallest difference of the photopic reflectivity is below 0 ° light incidence angle and then this layer system is deposited.

 Selecting an antireflective layer system from a specific pair of antireflective

Coatings (5, 6) can be made as to whether there are other conditions, namely in particular the features already listed above. Thus, it is provided in a development of the invention that the antireflection coating (5) is selected so that

 - The color of the residual reflection of the two antireflection coatings (5, 6) of a pair in the CIE xyz color system at 30 ° angle of incidence by not more than Δχ = 0.05, Ay = 0.05 is different, or

- The color of the residual reflection of the two antireflection coatings (5, 6) of a pair in the CIE xyz color system at 45 ° angle of incidence by not more than Δχ = 0.05, Ay = 0.05 differs.

 In particular, the invention is suitable for inorganic substrates. A preferred substrate is sapphire. This substrate is particularly high quality, hard and transparent, so that here the advantages of the invention, namely to provide a high-quality, hard and abrasion-resistant insensitive anti-reflective coating system come especially to advantage. In addition to sapphire but also other (single) crystals, such as CaF2, or

Glass ceramics or glasses, such as soda-lime glass, borosilicate glass,

Aluminosilicate glass, lithium aluminosilicate glass or optical glasses are used, for example glasses with the trade names NBK7, D263 or B270 (sold by SCHOTT AG). Particularly suitable for the layers with a high refractive index are silicon nitride (S13N4), aluminum nitride (AIN), aluminum oxide (Al2O3), as well as oxynitrides (Al _w Si _x NyOz) and mixtures of the materials mentioned. These materials not only have a high refractive index, but also a high hardness. Among the nitrides, in particular aluminum nitride and silicon nitride may be mentioned as suitable layer materials. The materials may be doped, or may not be in pure form. For example, aluminum nitride with a silicon content (eg between 0.05 and 0.25) or, conversely, silicon with a proportion of aluminum (again between 0.05 and 0.25, for example) can be used as the material for the higher-indexing layers. The lower refractive index layers have, in particular, a refractive index in the range from 1.3 to 1.6, preferably 1.45 to 1.5, at a wavelength of 550 nm, the layers with higher refractive index have a refractive index at a wavelength of 550 nm Range of 1.8 to 2.3, preferably 1.95 to 2.1.

 All the above-mentioned features in terms of reflectivity and color location can also be met according to a further development of the invention, if the layer thicknesses of all layers is further reduced to at most 0.8 times, more preferably at most 0.7 times, particularly preferably no more than 0.6 times the unreduced layer thicknesses.

 The invention is particularly suitable for small substrates. The substrate has

Preferably, an edge length or a diameter of less than 200 mm, Preferably, an edge length or a diameter of less than 150 mm, in particular of less than 100 mm, especially less than 50 mm. Such a surface can be uniformly coated with a PVD process.

 Preferably, the substrate is coated over its entire surface on at least one side, so that no masks are used. The antireflective coating is preferably seamless as a result of the simultaneous coating of the areas, as shown in FIG. All layers of the antireflection coating are preferably coated in one operation, without the substrate having to be taken out of the coating chamber in the meantime. In particular, it is also intended to coat several substrates simultaneously.

Brief description of the figures:

 Fig. 1 shows a transparent element with a six-layer antireflection coating.

Fig. 2 shows a transparent element with an antireflection coating with a seven-layer antireflection coating. Fig. 3 shows a transparent element with an antireflection coating on a non-planar surface.

 Fig. 4 schematically shows various shapes of substrates.

 5 shows color loci of the color of the residual reflectance for different incident light angles on a land and a main face of a comparative example,

 Fig. 6 shows color loci of the color of the residual reflectivity for different incident light angles on a land and a major surface of an antireflection coating according to the invention. Fig. 7 shows three diagrams (a), (b), (c), which for a plurality of antireflection coatings, the ratio of the layer thicknesses of the uppermost to the third uppermost layer is shown.

 In Fig. 8 two diagrams are shown, in which the ratio of the product of

Layer thicknesses of the two uppermost is applied to the product of the layer thicknesses of the underlying pair of layers for two different substrates.

 9 shows two diagrams in which the ratio of the layer thickness of the thickest low-index layer to the layer thickness of the lowest high-index layer are shown for a multiplicity of exemplary embodiments.

 In FIG. 10, the ratio of the difference between the layer thickness of the thickest and the thinnest layer to the sum of the layer thicknesses of these layers is shown for a large number of antireflection coatings on a sapphire substrate with a chamfer angle of 30 °.

 Fig. 11 shows two graphs with values of the ratio of the standard deviation of the layer thicknesses to the layer thickness of the thickest layer.

 Fig. 1 shows two partial images (a) and (b). In this case, the partial image (a) shows an example of a transparent element 1 according to the invention. The transparent element 1 comprises a transparent, in particular inorganic, substrate 3, for example made of glass. On the substrate 3, a multilayer antireflection coating 5 is deposited. This has at least six layers 51, 52, 53, 54, 55, 56. The layers 51, 53, 55 are high-refractive and the layers 52, 54, 56 have a low refractive index, so that the layers 51, 53, 55 have a higher refractive index than the layers 52, 54, 55. The layer materials are characterized by different hatchings. As can be seen from the illustration, layers with a higher refractive index 51, 53, 55 alternate with layers 52, 54, 56 with a lower refractive index. A high hardness and resistance of the antireflection coating 5 is in particular caused by the layers 51, 53, 55 with higher refractive index, which has a greater hardness than that

have low-refractive layers. The layer 56 forms the uppermost layer 60 of the antireflection coating and is a low refractive index layer. The transparent element 1 shown in partial image (b) now differs from the element 1 according to partial image (a) only in that in the antireflection coating 6 the layer thicknesses of all the layers 51-56 are each by a factor, accordingly by the same percentage are reduced. It results in a reduction Ad of

Total layer thickness. Since all layers are reduced in their thickness by the same factor, the ratio of the reduction Ad to the total layer thickness D also applies to the layer thicknesses of the individual layers. Each of the layers 51-56 is thus reduced in its thickness by a factor Ad / D. Such a situation can occur if the antireflection coating 5 according to the invention according to partial image (a) is partially deposited on a surface area inclined to the coating source. The layer thicknesses of the layers 51-54 can now be selected according to the invention so that given a refractive index of the layer materials and the substrate with a decrease in the layer thickness according to the change between the two partial images (a), (b) the color of the residual reflection and / or Reflectivity of the surface remains virtually unchanged. In particular, the color of the residual reflection at 0 ° angle of incidence with reduced layer thickness according to part of image (b) of the color at unreduced

Layer thicknesses measured in the CIE xyz color system do not differ by more than Δχ = 0.05, Δν = 0.05. Another, alternative or in particular additional criterion is the photopic reflectivity under different light incidence angles. In this case, the photopic reflectivity at 0 ° incidence angle with reduced layer thicknesses according to partial image (b) of the photopic reflectivity at 0 ° angle of incidence at undiminished

Layer thicknesses according to partial image (a) differ by no more than AR_ph = 1.5%. These criteria can also be met in the case of an antireflection coating 5 if the decrease in Ad

Layer thickness D at least 0.1 * d, ie at least 10%.

In general, the antireflective coating 5 can be designed such that it has all or most (many, preferably most, most preferably almost all, most preferably all) of the same thickness without undiminished layer thickness: a) The antireflection coating 5 has at 0 ° angle of incidence, a residual reflection of a predefined color (eg in the CIE color space), eg. Blue (eg x = 0.20 +/- 0.05, y = 0.20 +/- 0.05) or color neutral (eg x = 0.30 +/- 0.05, y = 0.32 +/- 0.05). b) The color of the residual reflection of the antireflection coating 5 at 30 ° angle of incidence differs from the color at 0 ° angle of incidence by no more than z. B. Δχ = 0.02, Δν = 0.02.

 c) The color of the residual reflection of the antireflection coating 5 at 45 ° angle of incidence differs from the color at 0 ° angle of incidence by no more than z. B. Δχ = 0.05,

Δν = 0.05).

 d) The photopic reflectivity of the antireflection coating 5 (weighted with the sensitivity curve of the human eye) at 0 ° angle of incidence is less than 1.5% (eg also less than 2%, preferably less than 1.5%, especially preferably less than 1.0%, very particularly preferably less than 0.8%).

 e) The photopic reflectivity of the antireflective coating 5 at 30 ° angle of incidence differs from the value below 0 ° angle of incidence by less than 0.2%, more preferably by less than 0.1%.

 f) The photopic reflectivity of the antireflection coating 5 at 45 ° angle of incidence differs from the value below 0 ° angle of incidence by less than 0.2%, more preferably by less than 0.1%.

 g) The average reflectivity of the antireflective coating 5 (averaged in

Wavelength range between z. B. 450 nm and 700 nm) at 0 ° angle of incidence is less than 1, 5%, preferably less than 1, 25%, more preferably less than 1, 0%.

 h) The average reflectivity of the antireflection coating 5 below 30 °

 Angle of incidence differs from the value below 0 ° angle of incidence by less than 0.5%, preferably by less than 0.2%, more preferably by less than 0.1%.

 i) The average reflectivity of the antireflection coating 5 at 45 ° angle of incidence differs from the value below 0 ° angle of incidence by less than 0.5%, preferably by less than 0.2%, more preferably by less than 0.1 %.

 j) The absolute reflectivity (maximum in the wavelength range between, for example, 450 nm and 700 nm) is less than 2%, preferably less than 1.5%, particularly preferably less than 1.0%, at an angle of incidence of 0 °.

k) the absolute reflectivity at 30 ° angle of incidence differs from the value below 0 ° angle of incidence by less than 0.5%, preferably by less than 0.2%, more preferably by less than 0.1%. I) the absolute reflectivity at 45 ° angle of incidence differs from the value below 0 ° angle of incidence by less than 0.5, preferably by less than 0.2%, more preferably by less than 0.1%.

 If the layer thickness of the antireflection coating 5 according to the invention 5 is reduced by 10%, preferably by 20%, more preferably by 30%, most preferably by 40%, or even by 50%, so that an antireflection coating 6 is obtained, as example Teilbild (b) of FIG. 1, the following features can be present individually or in combination: m) The color of the residual reflection of the antireflection coating 6 with uniformly reduced layer thicknesses of all layers at 0 ° angle of incidence differs from the color of the antireflection coating 5 undiminished layer thicknesses of all layers below 0 °

 Angle of incidence of not more than Δχ = 0.05, Δν = 0.05, preferably not more than Δχ = 0.03, Δν = 0.03, more preferably not more than Δχ = 0.02, Δν = 0.02, most preferably not more than Δχ = 0.01 , Δν = 0.01.

 n) The color of the residual reflection at 30 ° angle of incidence of the antireflection coating 6 with uniformly reduced layer thicknesses of all layers differs from the color of the antireflection coating 5 with undiminished layer thicknesses below 30 ° angle of incidence by not more than Δχ = 0.05, Δν = 0.05, preferably by not more than Δχ = 0.03, Δν = 0.03, more preferably by not more than Δχ = 0.02, Δν = 0.02, most preferably by not more than Δχ = 0.01, Δν = 0.01.

 o) The color of the residual reflection of the antireflection coating 6 with uniformly reduced layer thicknesses of all layers at 45 ° angle of incidence differs from the color of the antireflection coating 5 with undiminished layer thicknesses below 45 ° angle of incidence by not more than Δχ = 0.05, Δν = 0.05, preferably by not more than Δχ = 0.03, Δν = 0.03, more preferably by not more than Δχ = 0.02, Δν = 0.02, most preferably by not more than Δχ = 0.01, Δν = 0.01.

 p) The photopic reflectivity of the antireflection coating 6 with uniformly reduced layer thicknesses of all layers at 0 ° angle of incidence differs from the color of the antireflection coating 5 with undiminished layer thicknesses below 0 ° angle of incidence by not more than AR_ph = 1, 5%, preferably not more than AR_ph = 1%, more preferably not more than AR_ph = 0.5%, most preferably not more than AR_ph = 0.25%.

In the example shown in FIG. 1, the antireflection coating 5 consists of a total of six layers, with the lowermost layer 51 being a high-index layer. Such Layer system is favorable if the refractive index of the substrate is significantly lower than the refractive index of the higher refractive layers. In the case of a substrate with a

In contrast, refractive index greater than 1.65, it is advantageous to provide a lower refractive layer 50 in contact with the substrate. Such an example is shown in Fig. 2, also with a partial image (a) with undiminished layer thicknesses of all layers and a partial image (b) with a similar anti-reflection coating 6, but in which all layers by the same percentage, or by the same factor are reduced in thickness.

 In general, therefore, the embodiment of FIG. 2 is based on the fact that a substrate 3 is coated with an antireflection coating 5 according to the invention, wherein the substrate 3 has a refractive index above 1.65, wherein the bottom layer 50 is a layer with a lower refractive index ,

 Preferably, the substrate 3 of this embodiment is a sapphire. The transparent element may then be, for example, a watch glass or a magnifier for a watch glass, as used to increase the date display. In addition to sapphire, other (single) crystals, such as, for example, CaF 2 or glass ceramics, for example soda-lime glass, borosilicate glass, aluminosilicate glass, lithium aluminosilicate glass, optical glasses, for example glasses with the trade names NBK 7, can be used as the substrate material. D263 or B270.

 Fig. 3 shows an important application for the invention. The layer system is particularly suitable for non-planar surfaces of substrates by the inventive design of the layer thicknesses. In general, provision is made for the antireflection coating 5 to cover different surface regions 30, 32 of the substrate 3 which differ in terms of their inclination or with respect to the direction of their surface normal, the layer thickness of the antireflection coating (and as explained the layer thicknesses of all layers the coating) varies depending on the inclination of the surface areas.

 In the case of a more or less directed deposition method, different layer thicknesses of the antireflection coating 5 then result depending on the local inclination of the surface. As shown, the substrate 3 may in particular have an edge region whose inclination differs from a flat central region. A typical case of such a surface area 32 is a chamfer 31. According to a preferred

Embodiment of the invention is generally provided, without limitation to the illustrated example, that the antireflective coating 5 both the center region as the first

Surface area 30, as well as the chamfer 31 or more generally a border area as another Surface layer 32 covered, wherein the layer thicknesses of the layers of the antireflection coating 5 on the chamfer 31 or the edge region are reduced compared to the layer thicknesses in the central region. Accordingly, the total layer thickness d 'of the antireflection coating 5 in the edge region is smaller than the layer thickness d in the flat central region.

 The property of a layer system according to the invention, with regard to the optical

Properties to be tolerant to thickness variations is particularly advantageous when distinct angles between the surface normals of different coated

Surface areas are present. Therefore, it is provided in development of this embodiment of the invention that between the surface normal of the chamfer 31 or the

Border area and the surface normal of the center area an angle of at least 20 ° is included.

 In the case of a directional deposition method, such as in particular when sputtering on a surface not oriented perpendicularly to the beam direction, that is to say in the example shown in FIG. 3, this may result in an altered density or chemical composition (eg degree of oxidation). the situation compared with a perpendicular to

 Beam direction oriented surface come. The modified density then typically involves a somewhat different refractive index despite a similar or constant composition of the layer material. This effect can already be taken into account in the design of the layer system. In any case, according to one embodiment of the invention, it is provided that at least some of the layers of the antireflection coating have a refractive index which varies with the thickness of the layer and / or the inclination of the surface. In most cases, the refractive index is smaller, depending on the composition and deposition of the

Refractive index at a smaller layer thickness but also be larger.

 4 shows three examples of further substrates 3 with surface regions 30, 32 of different inclination. The various surface areas are generally subdivided into main and secondary areas, the scale being the proportion of the total area. The area ratio of the minor surface is less than 50%, preferably less than 30%, in particular less than 10%, or even less than 5%. The inclination of the major surfaces in Examples (a), (b), (c) is parallel to the opposite side surface of the generally disk-shaped substrate 3. As in Example (a), a surface region 32 may also be domed, in particular dome-shaped. This changes the inclination in this

Surface area 32 continuous. Also a total arched, for example as a lens However, formed substrate may be provided. Edge regions as surface regions 32 with an inclination differing from the main surface can be formed as a chamfer or flat surface, or even curved, as likewise illustrated in example (a).

 In example (b), the surface area 30 is subdivided into a plurality of terraced areas. The transitions between the height levels form surface regions 32 with a different inclination, which in turn may be constant or varies continuously in the form of a curvature.

 In example (c), the main surface has one or more depressions, the transition also being formed here by differently inclined edge regions 32. An edge area can also be curved convexly as shown.

 In general, it is advantageous to weight the aspects of color uniformity and antireflection coating differently in a subdivision into the main and secondary surface. For the

Main surface is a good anti-reflection especially important. Here, the average reflectivity in the visible spectral range, in particular also the photopic reflectivity, should preferably be less than 5%, more preferably less than 3%, most preferably less than 1.5%. The

Main surface also defines the color of the residual reflection perceptible to the viewer.

Preferably, this is color neutral, but may also be bluish, for example. In the surface area with a smaller area, ie the secondary area, the color of the residual reflection plays a greater role. A deviation from the color of the main surface is perceived as more conspicuous than a locally larger reflection. According to one embodiment of the invention, the antireflection coating may generally be designed such that the average or average reflectivity on the minor surface is higher by a factor of 2 to 5 than on the major surface, but the photopic reflectivity is still lower than that of the uncoated substrate. In the case of sapphire substrate, the average reflectivity at 0 ° incidence of light, ie vertical incidence of light 7.5% to 8%, at 45 ° light incidence 30% to 50%. In the embodiments described so far, the layer system is more specific

Direction of light incidence optimized in each case with the same angle with respect to the respective normal of the surface regions. In other words, the layer system is designed so that differently inclined surface areas in each case have, for example, vertical light incidence as the same colors of the residual reflection and / or reflectivity as low as possible. Under illumination with a real light source, however, the case occurs that the light incident angle of the light varies depending on the inclination of the surface area. Therefore, according to the invention In particular, it is also provided that the antireflection coating 5 has at least one of the following features:

 - The colors of the residual reflection of the surface regions (30, 32) of different inclination differ in the CIE xyz color system by not more than Δχ = 0.05, Δν = 0.05, preferably not more than Δχ = 0.03, Δν = 0.03, more preferably not more than Δχ = 0.02, Δν = 0.02, when the transparent element (1) is irradiated with light which hits perpendicular to one of the surface areas,

 - The photopic reflectivities of the surface regions of different inclination differ from each other by not more than AR_ph = 1.5%, when the transparent element (1) is irradiated with light, which meets perpendicular to one of the surface regions. Again, the inclination is significantly different, so that between the normals of the surface areas an angle of at least 20 °, preferably at least 30 °.

 The invention is not limited to the embodiments, but can be varied within the scope of the subject of the claims varied. It can be different

Embodiments are also combined with each other. Thus, an antireflection coating can be applied to both sides of a disc-shaped substrate. The antireflection coatings can then also have different colors of the residual reflection. The invention is furthermore not limited to six- or seven-ply coatings, as shown by way of example in FIGS. 1 and 2. It can also be provided more layers, such. 9 layers in example 2 described below. However, it is generally preferred that the antireflective coating 5 has at most twenty, particularly preferably at most fifteen, layers in order to limit the production costs and to obtain the abrasion resistance.

 Embodiments of layer systems according to the invention will be described below.

 Example 1 is a theoretical or calculated example of an antireflection coating (7 layers) on sapphire:

Among other things, the fitting process leads to the following theoretical solution for a system which is to be color neutral and antireflective on the main surface 1, which remains color neutral and slightly reflective under viewing angle, and retains this property if the top layer is damaged by abrasion. In addition, there is a second surface which has an angle of 45 ° to the first surface and if this second Area viewed from one direction, which is normal to the first surface +/- 10 °, then this second surface appears color-neutral and less reflective than uncoated.

Surface 1 coated below 0 °

 Color Location Target x 0.333

 Color location target y 0.333

 Color locus CIE x considered below 0 ° 0.327

 Color locus CIE y considers below 0 ° 0.333

 Color Deviation x from the target is below 0 ° 0.006

 Color locus deviation y from the target viewed below 0 ° 0.000

 Color locus CIE x considered below 20 ° 0.334

 Color locus CIE y considers below 20 ° 0.333

 Chromaticity deviation x from target viewed below 20 ° 0.001

 Color locus deviation y from the target is below 20 ° 0.000

 photopic eflectivity target <1.00%

 photopic reflectivity is below 0 ° 0.82%

 photopic reflectivity considered below 20 ° 0.87%

Surface 1: Thickness of last layer reduced by 10%:

 Color locus CIE x considered below 0 ° 0.318

 Color locus CIE y is considered below 0 ° 0.293

 Color Location Deviation x from target viewed below 0 ° 0.015

 Color deviation y from the target viewed below 0 ° 0.040

 Photopic reflectivity considered below 0 ° 1.27% coated below

 Surface 2 (chamfer)

 45 °

Color Location Target x 0.333 Color location target y 0.333

 Color locus CIE x considered at 45 ° 0.334

 Color locus CIE y considers at 45 ° 0.330

 Chromaticity deviation x from the target viewed below 45 ° 0.001

 Color deviation y from the target viewed below 45 ° 0.003

 Color locus CIE x considers below 35 ° 0.337

 Color locus CIE y considers below 35 ° 0.373

 Color Deviation x from target viewed below 35 ° 0.004

 Color deviation y from the target viewed below 35 ° 0.040

 Color locus CIE x considers below 55 ° 0.342

 Color locus CIE y considers below 55 ° 0.309

 Color Location Deviation x from target viewed below 55 ° 0.009

 Color deviation y from the target viewed below 55 ° 0.024

 photopic eflectivity target <4.00%

 Photopic reflectivity viewed below 0 ° 2.98%

The surface 2 thus corresponds to a chamfer inclined at 45 ° with respect to a flat central region. The embodiment shows that with the layer system with the above-mentioned thicknesses of the layers 1 to 7 (corresponding to the layers 50-56 in FIG. 2) also has good antireflection properties on the bevel and the color locations differ only slightly.

 Example 2 is an antireflective (AR) design on sapphire (9 layers).

 The following tables show values from the theoretical simulation of the design as well as measured values at the deposited layer system. This is a coating that should be color neutral but slightly bluish, low reflectance, this

Features in a wide viewing angle range of 0 ° to 45 °. Furthermore, these properties are retained when a harsh abrasion test damages the top layer. In addition, the substrate has a chamfer of 60 °, which, viewed normal to the main surface +/- 10 ° (ie even below 60 ° +/- 10 °) is also color neutral and less reflective. The abrasion test used was the modified Bayer test described at the beginning, in which 2 kg of corundum sand (Al 2 O 3) was rubbed 8000 times at 150 cycles / minute due to its inertia over a 100 mm reciprocating substrate.

For the most part, the many-sided challenges are well met in the practical example and shown by the fact that the corresponding design represents a suitable implementation of the invention. Although the exact values on the small bevel were not exactly measurable. However, a visual comparative evaluation was performed under microscope: the visual In fact, the impression is that the chamfer is much more color neutral and less reflective than a standard AR coating.

Surface 1: coated under 0 ° design measured

 Color Location Design Target x 0.295

 Color location design target y 0.300

 Color locus CIE x considers 0.294 0.262 below 0 °

Color locus CIE y considers below 0 ° 0.293 0.285

Color locus deviation x from the target viewed below 0 ° 0.001 0.033

Color locus deviation y viewed from the target below 0 ° 0.007 0.015

 Color locus CIE x considers below 30 ° 0.290 0.263

Color locus CIE y is considered below 30 ° 0.289 0.280

Color locus deviation x from the target viewed below 30 ° 0.005 0.032

Color locus deviation y from the target considered below 30 ° 0.011 0.020

 Color locus CIE x considered at 45 ° 0.311 0.314

Color locus CIE y considered at 45 ° 0.319 0.319

Color locus deviation x from target viewed below 45 ° 0.016 0.019

Color locus deviation y viewed from the target below 45 ° 0.019 0.019 photopic eflectivity target <1.5%

 photopic reflectivity viewed below 0 ° 1.22% 1.52% photopic reflectivity viewed below 30 ° 1.15% 1.13% photopic reflectivity viewed at 45 ° 1.63% 1.31%

Surface 1: Thickness of last layer reduced by 10%: Design

 Color locus CIE x considered below 0 ° 0.267

 Color locus CIE y considers below 0 ° 0.285

 Color locus deviation x from target viewed below 0 ° 0.028

 Color locus deviation y viewed from the target below 0 ° 0.015

 Color locus CIE x considers below 30 ° 0.290

 Color locus CIE y considers below 30 ° 0.291

 Color locus deviation x from the target viewed below 30 ° 0.005

 Color locus deviation y from the target is under 30 ° 0.009

 Color locus CIE x considered at 45 ° 0.360

 Color locus CIE y considers below 45 ° 0.321

 Color locus deviation x from target viewed below 45 ° 0.065

 Color locus deviation y from the target is below 45 ° 0.021

 photopic reflectivity viewed below 0 ° 0.68% photopic reflectivity viewed below 30 ° 0.77%

photopic reflectivity considered below 45 ° 1.45% Area 1: Thickness of last layer reduced by 20%: Design

 Color locus CIE x considered below 0 ° 0.266

 Color locus CIE y considered below 0 ° 0.281

 Color locus deviation x from target viewed below 0 ° 0.029

 Color locus deviation y from the target is below 0 ° 0.019

 Color locus CIE x considered below 30 ° 0.325

 Color locus CIE y considers below 30 ° 0.301

 Color locus deviation x from target viewed below 30 ° 0.030

 Color locus deviation y from the target viewed below 30 ° 0.001

 Color locus CIE x considers below 45 ° 0.402

 Color locus CIE y considers at 45 ° 0.317

 Color locus deviation x from the target viewed below 45 ° 0.107

 Color locus deviation y from the target is below 45 ° 0.017

 photopic eflectivity viewed below 0 ° 0.67% photopic reflectivity viewed below 30 ° 0.91% photopic reflectivity viewed at 45 ° 1.82%

Surface 1: measured according to Bayer test (sand abrasion test) design

 Color locus CIE x considered below 0 ° 0.256

Color locus CIE y considers below 0 ° 0.296

Color locus deviation x from target viewed below 0 ° 0.039

Color locus deviation y viewed from the target below 0 ° 0.004

 Color locus CIE x considers below 30 ° 0.240

Color locus CIE y considers below 30 ° 0.291

Color locus deviation x from the target viewed below 30 ° 0.055

Color locus deviation y from the target is under 30 ° 0.009

 Color locus CIE x considers below 45 ° 0.276

Color locus CIE y considers below 45 ° 0.324

Color locus deviation x from the target viewed below 45 ° 0.019

Color locus deviation y viewed from the target below 45 ° 0.024 photopic reflectivity viewed below 0 ° 1.59% photopic reflectivity viewed below 30 ° 1.35% photopic reflectivity viewed at 45 ° 1.79%

Surface 2 (chamfer): coated coated under 60 ° design

 Color Location Design Target x 0.295

 Color location design target y 0.300

 Color locus CIE x considers below 60 ° 0.305

 Color locus CIE y considers below 60 ° 0.274

 Color locus deviation x from target viewed below 60 ° 0.010

Color locus deviation y from the target is below 60 ° 0.026 Color locus CIE x considers below 50 ° 0.282

 Color locus CIE y considers below 50 ° 0.253

 Color locus deviation x from target viewed below 50 ° 0.013

 Color locus deviation y from the target viewed below 50 ° 0.047

 Color locus CIE x considered below 70 ° 0.323

 Color locus CIE y considers below 70 ° 0.302

 Color locus deviation x from target viewed below 70 ° 0.028

 Color locus deviation y from the target is below 70 ° 0.002

FIGS. 5 and 6 show as color locus diagrams in the CIE 1931 color space two examples of color values of the residual reflection at different light incidence angles for

Coatings on sapphire substrates with a chamfer. The diagrams show the limitation of the color space. Both layer systems were optimized for a target color location on the major surface of x = 0.31, y = 0.31.

 In both examples, the chamfer is angled at 55 ° to the main surface. The antireflective coating covers the major surface and the chamfer. For the

As shown in Fig. 3, calculation of the optical properties was assumed to reduce the layer thickness on the land due to a directional coating process.

 The layer thicknesses of the example of FIG. 5 on the main surface are in the

Order from the lowest to the highest position:

 34.8 nm / 27.6 nm / 38 nm / 140.4 nm / 91, 6 nm

Angulation the following reduced layer thicknesses:

 20 nm / 15.9 nm / 21, 8 nm / 80.5 nm / 52.5 nm.

 In the example shown in FIG. 6, the layer thicknesses ascend from the lowest to the highest layer on the main surface:

 44.8 nm / 19.9 nm / 62.5 nm / 28.9 nm / 30.9 nm / 48.2 nm / 20.4 nm / 159.8 nm / 76.37 nm.

 On the chamfer, the corresponding layer thicknesses are:

44.8 nm / 19.9 nm / 62.5 nm / 28.9 nm / 30.9 nm / 48.2 nm / 20.4 nm / 159.8 nm / 76.37 nm.

 The color values of the main surface are shown as dots in the diagrams of FIGS. 5 and 6, and the values of the chamfer as open triangles. Furthermore, the y color values are entered in the diagrams.

 As can be seen in the comparison of the diagrams, is in an inventive

Antireflection coating, the change in color values between bevel and main surface as a whole small, with little change in the color depending on the angle of light incidence occurs. All values are close together in the color locus diagram of FIG

Comparative example are approximately widened along a line.

 The values are given below in detail in the two tables. In the table, the indications EW denote the angle of incidence, R the reduction of the layer thickness of the uppermost layer and R_ph the photopic reflectivity

 Example 1 (Fig. 5)

 Color for

Angle, comment

Abrasion and

Do not chamfer

optimized EW R [nm] R_ph [%] X y Δ (χγ)

 0 °, 100% layer (new):

0 ° 0 0.72 0.310 0.310 0.030 perfect

 15 ° 0 0.73 0.315 0.312 0.025

 30 ° 0 0.87 0.326 0.335 0.006 strong

 Color deviations under different

45 ° 0 1, 67 0.325 0.368 0.038 viewing angle

60 ° 0 5.27 0.312 0.356 0.031

 Strength

 coating

 Color deviations after

 0 ° 10 0.97 0.344 0.338 0.015 Abrasion Main surface

 Strength

 below 0 °

 Color deviations after

15 ° 10 z1, 03 0.346 0.346 0.021 Abrasion

 Strength

 Color deviations after

30 ° 10 1, 30 0.343 0.370 0.041 Abrasion

 Strength

 Color deviations after

45 ° 10 2.28 0.327 0.367 0.048 Abrasion

60 ° 10 6.11 0.311 0.352 0.029

 0 ° 0 7.64 0.460 0.451 0.176 very strong

 15 ° 0 8,03 0,452 0,448 0,169 Color variations among different

30 ° 0 9.23 0.432 0.439 0.148

 Viewing angles:

Coating 45 ° 0 11, 67 0.401 0.419 0.112 bright / brilliant / brillia to 60 ° 0 17.16 0.362 0.387 0.064 ntes orange

 Bevel 0 ° 10 7.78 0.418 0.431 0.133 very strong

 below 55 °

 15 ° 10 8.08 0.412 0.427 0.126 Color variations among different

30 ° 10 9.05 0.344 0.415 0.105

 viewing angles

45 ° 10 11, 10 0.368 0.394 0.073 after abrasion

60 ° 10 16.12 0.340 0.366 0.036

In the following, further features of antireflection coatings according to the invention are discussed with regard to the layer thicknesses of the layers. The features of the layer thickness ranges apply in particular at a wavelength of 550 nm in the range of 1, 3 to 1, 6, preferably 1, 45 to 1, 5 for the layers with a lower refractive index and a refractive index at a wavelength of 550 nm in the range of 1.8 to 2.3, preferably 1.95 to 2.1 for the higher refractive index layers. One characteristic of suitable coatings, according to one embodiment, is the ratio of the layer thicknesses of the uppermost layer to the third uppermost layer, these are generally the uppermost layer of lower refractive index and the second uppermost layer of lower refractive index. The ratio of the layer thickness of According to one embodiment of the invention, the uppermost layer to the layer thickness of the third uppermost layer is in a range of 0.5 to 8.5, preferably in the range of 2 to 8, more preferably in the range of 3 to 8, without limitation to the exemplary embodiments. 7 shows three diagrams (a), (b), (c) in which the abovementioned ratio for a multiplicity of optimized antireflection coatings is shown. In each case the ratio is plotted on the ordinate of the diagrams, each point in the diagrams represents an antireflection coating. Graph (a) plots the ratio for coatings, that for a sapphire substrate with a 55 ° angled facet as the second surface area versus the major surface as the first surface area. Diagram (b) shows further examples, here the coatings for a borosilicate glass and an under 55 ° angled facet are optimized. The examples of diagram (c) are optimized coatings for a sapphire substrate with a 30 ° angled facet. As can be seen, the ratios are in the range of 0.5 to 8 for all three configurations, with only one example having a very thick third uppermost layer in diagram (b) having a ratio of less than 2.

 According to yet another embodiment of the invention, it is provided that, in particular with an inclination of the second surface area to the first surface area in the range of 50 ° to 60 °, the ratio of the product of the layer thicknesses of the uppermost pair of layers to the product of the layer thicknesses of the second uppermost pair of layers in FIG one of the ranges from 8 to 22 or 60 to 140. In other words, the layer thickness here is in the range of 8 to 140, excluding a range between 22 and 60. In the example of FIG. 1, the aforementioned ratio V would be formed by (layer thickness layer 56 x layer layer layer 55) / (layer layer layer 54 x layer layer layer 53).

 FIG. 8 shows two diagrams (a), (b) in which a plurality of

Embodiments on the ordinate the ratio is plotted. The antireflection coatings correspond to those of the diagrams (a) and (b) of FIG. 7.

 Accordingly, graph (a) shows the ratio for the facet being angled at a 55 ° angled sapphire substrate and (b) the ratio for the antireflective coatings optimized on a borosilicate glass substrate with a 55 ° angled facet. If the above-described features are used as constraints, the cost of optimizing the coating systems can be reduced accordingly, since the number of possibilities and thus the calculation effort is significantly reduced.

Accordingly, it is provided in a development of the method that at least one of Antireflective coatings of the pair of antireflective coatings for which at least one of the parameters of residual reflection color and photopic reflectivity is calculated, selected to satisfy at least one of the following conditions:

 the ratio of the layer thickness of the uppermost layer of the antireflection coating 5 to

Layer thickness of the third uppermost layer is in a range of 0.5 to 8.5, preferably in the range of 2 to 8, particularly preferably in the range of 3 to 8,

 the ratio of the product of the layer thicknesses of the uppermost pair of layers to the product of the layer thicknesses of the second uppermost pair of layers is in one of the ranges from 8 to 22 or 60 to 140.

 An influence on the optical properties with respect to the invariance below

Coating of differently inclined surfaces also has the ratio of the thickest high and low refractive layers. 9 shows two diagrams in which, for a large number of exemplary embodiments, the ratio of the layer thickness of the thickest low-index layer to the layer thickness of the lowest high-index layer is shown. Diagram (a) shows the relationship for a variety of embodiments on a sapphire substrate, with the embodiments optimized for either facets of 30 ° or 55 ° angles. Graph (b) shows the values of the ratio for antireflective coatings optimized for a borosilicate glass substrate with a facet angled at 55 °. It can be seen that in both cases the values contain an area in which no coatings with favorable properties occur. It will not

excluded that in these areas are also suitable coatings, but obviously these are at least less common. It can also be seen that the range is dependent on the refractive index of the substrate. In the case of borosilicate glass with a refractive index of 1.47 at 550 nm light wavelength, the range is around two, while in the case of a sapphire substrate with a refractive index of approximately 1.77, the range is around two. The dependence can be well represented by a factor (n-1) / (riBoro-1), where ΠΒΟΓΟ denotes the refractive index of the borosilicate glass, ie at 550 nm a value of 1.47. Thus, an advantageous feature of inventive antireflection coatings can be defined as follows: The ratio of the layer thickness of the thickest layer under the layers with a lower refractive index to the layer thickness of the thickest layer under the layers with higher

Refractive index is between 0.2 and 3 excepting a range of 1.5 / F (n) to 2.5 / F (n) where F (n) is a function of the refractive index n of the substrate and is given by F (n) = (n-1) / (riBoro-1), or with the refractive index of borosilicate glass F (n) = (n-1) / (0.47). Again, depending on the refractive index of the substrate for the process of making a transparent element, a corresponding constraint can be made to limit the choice of possible designs.

 In FIG. 10, the ratio of the difference between the layer thickness of the thickest and the thinnest layer to the sum of the layer thicknesses of these layers is shown for a large number of antireflection coatings on a sapphire substrate with a chamfer angle of 30 °. The points thus result according to the relationship (dmax-dmin) / (dmax + dmin), where dmax denotes the maximum layer thickness of all layers and dmin the minimum layer thickness of all layers of a suitable antireflection coating. The values of this ratio are similar for the other systems discussed here as examples, ie antireflective coatings on sapphire and borosilicate glass with a chamfer angle of 55 ° each. Without limiting to the embodiments shown, according to one embodiment of the invention, the value of this ratio (dmax-dmin) /

(dmax + dmin) at least 0.65.

 Characteristic of suitable antireflection coatings is also the

Ratio of the standard deviation of the layer thicknesses of the individual layers to the layer thickness of the thickest layer. Fig. 11 shows two diagrams with values of this ratio. Diagram (a) shows the values for the embodiments on a sapphire substrate and diagram (b) for a borosilicate glass substrate, each with a chamfer angle of 55 °. The values for the embodiments on a sapphire substrate with a bevel angled at 30 ° lie between the maximum values in the diagrams (a) and (b).

 Without limitation to the embodiments is therefore according to a

Embodiment of the invention provides that the ratio of standard deviation of the layer thicknesses of the layers to the layer thickness of the thickest layer of the antireflection coating in a range of 0.25 to 0.45. Again, a corresponding

Constraint to simplify the selection of possible appropriate designs.

Three exemplary embodiments of the quantity of antireflection coatings whose values are shown in FIGS. 7 to 11 are listed below. An antireflection coating on a sapphire substrate with a chamfer angle of 55 ° has the following layer thicknesses, wherein the data (h) and (I) designate high-index or low-index layers, respectively:

 Substrate / 17.5 nm (I) / 17.25 nm (h) / 13.45 nm (I) / 9.6 nm (h) / 32.4 nm (I)

/ 20.4 nm (h) / 13.45 nm (I) / 237.9 nm (h) / 94.3 nm (I).

 An antireflection coating on a sapphire substrate with a chamfer angle of 30 ° has the following layer thicknesses, wherein the statements (h) and (I) designate high- or low-index layers, respectively:

 Substrate / 24.9 nm (I) / 28.15 nm (h) / 34.6 nm (I) / 165.4 nm (h) / 20.3 nm (I)

/ 150 nm (h) / 93.4 nm (l).

 An antireflection coating on a borosilicate glass substrate with a chamfer angle of 55 ° has the following layer thicknesses, wherein the data (h) and (I) designate high- and low-index layers, respectively:

 Substrate / 268.7 nm (h) / 24.7 nm (l) / 45.3 nm (h) / 49.6 nm (l) / 30.1 nm (h) / 154.3 nm (l).

 The invention can be used wherever special requirements are placed on the mechanical properties of antireflection coatings. In addition to the application as watch glasses or magnifiers for watch glasses, the invention can also be used in the field of architecture, consumer electronics and optical components. In the field of consumer electronics, the invention is particularly suitable for cover glasses of smartphones, smartwatches, notebooks, LCD displays, eyeglasses, 3D glasses, head-up displays.

Claims

Transparent element (1) comprising  a transparent substrate (3) and on this substrate (1)  a multilayer antireflective coating (5) comprising at least six plies, wherein high refractive index plies (51, 53, 55) alternate with lower refractive index plies (50, 52, 54, 56), and wherein  the higher refractive index layers (51, 53, 55) have greater hardness than the lower refractive index layers (50, 52, 54, 56), and the uppermost layer (56, 60) of the multilayer antireflective coating (5 ) is a lower refractive index layer, and wherein  - The substrate has at least two surface regions (30, 32), which differ in their inclination, wherein  the antireflective coating (5) covers the surface areas (30, 32) of different inclination, and wherein for the antireflective coating (5) on the Surface areas (30, 32) of at least one of the following features:  - The colors of the residual reflection respectively at 0 ° angle of incidence on the Surface areas (30, 32) differ from one another in the CIE xyz color system by no more than Δχ = 0.05, Δν = 0.05, preferably not more than Δχ = 0.03, Δν = 0.03, particularly preferably not more than Δχ = 0.02, Δν = 0:02,  - The photopic reflectivities at 0 ° angle of incidence of the surface regions (30, 32) differ from each other by not more than AR_ph = 1 .5%. Transparent element (1) according to the preceding claim, characterized in that the antireflection coating (5) has at least one of the following features:  - The colors of the residual reflection of the surface regions (30, 32) of different inclination differ in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, preferably not more than Δχ = 0.03, Ay = 0.03, more preferably not more than Δχ = 0.02, Ay = 0.02, when the transparent element (1) is irradiated with light which impinges perpendicularly on one of the surface areas (30, 32), - The photopic reflectivities of the surface areas of different inclination do not differ from each other by more than AR_ph = 1.5% when the transparent element (1) is irradiated with light which is perpendicular to one of the  Surface regions meets, between the normals of the surface regions (30, 32) is an angle of at least 20 °, preferably at least 30 °. Transparent element (1) according to one of the preceding claims, characterized in that the layer thickness of the antireflection coating (5) varies depending on the inclination of the surface regions (30, 32). Transparent element according to the preceding claim, characterized in that the antireflection coating has at least one of the following features: with reduced layer thicknesses by a factor k which is smaller than 0.9, the color of the residual reflection differs at a light incidence angle arccos (k) from the color below 0 ° light incidence angle with unreduced layer thicknesses of the layers (50-56) in the CIE xyz Color system by not more than Δχ = 0.05, Δν = 0.05, preferably not more than Δχ = 0.03, Δν = 0.03, more preferably not more than Δχ = 0.02, Δν = 0.02,  with reduced layer thicknesses by a factor k which is smaller than 0.9, the color of the residual reflection under an angle of incidence arccos (k) no longer differs from the color at 0 ° light incidence angle with unreduced layer thicknesses of the layers (50-56) as AR_ph = 1.5%. Transparent element (1) according to the preceding claim, characterized  in that the substrate (3) has a flat central area (30) and a chamfer (31) or edge area (32), and wherein the antireflective coating (5) has both the central area (30) and the chamfer (31 ) or the edge region (32), and wherein the layer thicknesses of the layers (50-56) of the antireflection coating (5) on the chamfer (31) or the edge region (32) with respect to the layer thicknesses in  Center area (30) are reduced. 6. Transparent element (1) according to the preceding claim, wherein between the surface normal of the chamfer (32) or the edge region (32) and the Surface normal of the center region included an angle of at least 20 ° becomes. 7. Transparent element (1) according to one of claims 2 to 4, characterized  in that at least some of the layers (50-56) of the antireflective coating (5) have a thickness that varies with the thickness of the layer or the inclination of the surface  Have refractive index. 8. Transparent element (1) according to one of the preceding claims, characterized  characterized in that the layers (51-54) are selected with respect to their thickness for given refractive indices so that  - The color of the residual reflection at an angle of incidence of between 30 ° - arccos (0.9) = 4 ° and 30 ° + arccos (0.9) = 56 °, at 10% reduced layer thicknesses from the color below 30 ° angle of incidence at unreduced Layer thicknesses in the CIE xyz color system by no more than Δχ = 0.05, Ay = 0.05 is different, or  - The color of the residual reflection at an angle of incidence of between 45 ° - arccos (0.9) = 19 ° and 45 ° + arccos (0.9) = 71 °, decreased by 10%  Layer thicknesses of the color below 45 ° angle of incidence with unchanged layer thicknesses in the CIE xyz color system differ by no more than Δχ = 0.05, Ay = 0.05. 9. Transparent element (1) according to one of the preceding claims, characterized  characterized in that the layers (51-54) are selected with respect to their thickness for given refractive indices so that when the layer thickness of all layers is reduced by 10%, the photopic reflectivity at 0 ° incidence angle is not more than  AR_ph = 1%, more preferably not more than AR_ph = 0.5%, most preferably not more than AR_ph = 0.25% deviates from the value at undiminished layer thicknesses. 10. Transparent element (1) according to one of the preceding claims, characterized by at least one of the following features:  - The color of the residual reflection on the antireflective coating (5) at 0 ° angle of incidence at undiminished layer thicknesses differs from the color below 0 ° Incidence angle in the CIE xyz color system by no more than Δχ = 0.05, Ay = 0.05 at reduction the layer thickness of all layers by 20%, preferably 30%, particularly preferably 40%, - The photopic reflectivity at 0 ° angle of incidence at 20%, preferably reduced by 30%, more preferably by 40% layer thicknesses of all layers differs from the photopic reflectivity at 0 ° angle of incidence with unreduced layer thicknesses by no more than AR_ph = 1 .5%,  - the color of the residual reflection on the antireflection coating (5) at 30 ° angle of incidence differs from the color at 0 ° angle of incidence in the CIE xyz color system by no more than Δχ = 0.02, Ay = 0.02,  - the color of the residual reflection at 45 ° angle of incidence differs from the color at 0 ° angle of incidence by not more than Δχ = 0.05, Ay = 0.05,  the photopic reflectivity at 0 ° angle of incidence is less than 1.5%,  the maximum of the reflectivity in the wavelength range between 450 nm and 700 nm, is less than 1, 5% at 0 ° incidence angle,  the absolute value of the difference of the photopic reflectivity at an angle of incidence of 30 ° to the photopic reflectivity at 0 ° incidence angle is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%,  the absolute value of the difference of the photopic reflectivity at an angle of incidence of 45 ° to the photopic reflectivity at 0 ° angle of incidence is absolutely less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%,  the average reflectivity, averaged in the wavelength range between 450 nm and 700 nm at 0 ° angle of incidence, is less than 1.5%,  the absolute value of the difference of the average reflectivities at 30 ° incidence angle and below 0 ° incidence angle, averaged in the wavelength range between 450 nm and 700 nm, is absolutely less than 0.5%, preferably less than 0.3%, more preferably less than 0, 1 %,  the absolute value of the difference of the average reflectivities at angles of incidence of 45 ° and angles of incidence averaged in the wavelength range between 450 nm and 700 nm is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1 % - The absolute value of the difference of the maxima of the reflectivities in the wavelength range of 450 nm to 700 nm under 30 ° incidence angle and less than 0 ° incidence angle less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%. 1. Transparent element (1) according to the preceding claim, characterized by at least one of the features:  the photopic reflectivity at 0 ° angle of incidence is less than 1%, preferably less than 0.8%,  the absolute value of the difference of the average reflectivity in  Wavelength range between 450 nm and 700 nm at 30 ° incidence angle to the average reflectivity in the wavelength range between 450 nm and 700 nm at 0 ° incidence angle is less than 0.1%,  the absolute value of the difference between the average reflectivities at 45 ° incidence and at 0 ° incidence, averaged over the wavelength range between 450 nm and 700 nm, is less than 0,5%  - the average reflectivity, averaged in the wavelength range between 450 nm and 700 nm at 0 ° angle of incidence is less than 1, 0%. 2. Transparent element (1) according to one of the preceding claims, wherein the layers (51-56) are selected with respect to their thickness for given refractive indices such that when the layer thickness of the uppermost layer (60) is reduced by 10% or by 10 nm, depending on which of these two cases gives the lower remaining layer thickness, and at the same layer thickness of the remaining layers (50-55) at least one of the following features applies:  - The color of the residual reflection at 0 ° angle of incidence at a reduced layer thickness differs from the color at 0 ° light incidence angle with undiminished layer thickness of the top layer (54) in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, preferably not more as Δχ = 0.03, Ay = 0.03, more preferably not more than Δχ = 0.02, Ay = 0.02, - The photopic reflectivity at 0 ° angle of incidence with a reduced layer thickness differs from the photopic reflectivity at 0 ° incidence angle with undiminished layer thickness by not more than AR_ph = 1.5%. 13. Transparent element (1) according to one of the preceding claims, characterized in that the substrate (3) is a sapphire substrate. 14. Transparent element (1) according to one of the preceding claims, characterized  in that the substrate (3) has a refractive index above 1.65 and the bottom layer (50) is a layer with a lower refractive index. 15. Transparent element (1) according to one of the preceding claims, characterized by layers (51, 53) with a high refractive index of at least one of the materials aluminum oxide (Al 2 O 3), nitride or oxynitride. 16. Transparent element (1) according to one of the preceding claims, characterized  in that the antireflection coating (5) has at most twenty, preferably at most fifteen layers. 17. Transparent element (1) according to one of the preceding claims, characterized by at least one of the following features:  the ratio of the layer thickness of the uppermost layer (56) of the antireflection coating (5) to the layer thickness of the third uppermost layer (54) is in a range from 0.5 to 8.5, preferably in the range from 2 to 8, particularly preferably in Range from 3 to 8 the ratio of the product of the layer thicknesses of the uppermost pair of layers to the product of the layer thicknesses of the second uppermost pair of layers is in one of the ranges from 8 to 22 or 60 to 140,  the ratio of the layer thickness of the thickest layer under the layers of lower refractive index to the layer thickness of the thickest layer under the layers of higher refractive index is between 0.2 and 3, wherein a range from 1, 5 / F (n) to 2.5 / F (n), where F (n) is given by F (n) = (n-1) / (0.47) and n den  Refractive index of the substrate denotes the ratio of the standard deviation of the layer thicknesses of the layers to the layer thickness of the thickest layer of the antireflection coating is in a range of 0.25 to 0.45. 18. Transparent element (1) according to one of the preceding claims, designed as a watch glass or magnifying glass of a watch glass. 19. A process for producing a transparent element (1) comprising the steps of:  it is for at least a pair of antireflective coatings (5, 6), which at least six layers (50, 51, 52, 53, 54, 55, 56) include, wherein layers with high  Refractive index (51, 53, 55) alternate with lower refractive index layers (50, 52, 54, 56), wherein the higher refractive index layers (51, 53, 55) have greater hardness than the layers (50, 52, 54, 56) having a lower refractive index, and wherein the uppermost layer (56, 60) of the multilayer antireflective coating (5) is a lower refractive index layer, taking into account the refractive index of the substrate (3) of at least one of the parameters  - Color of the residual reflection and  - Photopic reflectivity  calculated, with the two antireflection coatings in terms of  Different layer thicknesses of all layers, such that the layer thicknesses of all the layers in an antireflection coating (6) is reduced by a common factor which has a value between 0 and 0.9 compared to the layer thickness of the other antireflection coating (5), and wherein it is checked whether at least one of the conditions is fulfilled for both antireflection coatings (5, 6):  - the color of the residual reflection at 0 ° angle of incidence with uniformly reduced layer thicknesses differs from the color below 0 ° light incidence angle with unreduced layer thicknesses in the CIE xyz color system by no more than Δχ = 0.05, Ay = 0.05,  - The photopic reflectivity at 0 ° angle of incidence with uniformly reduced layer thickness of all layers (50, 51, 52, 53, 54, 55, 56) differs from the photopic reflectivity at 0 ° incidence angle at undiminished layer thicknesses by no more than AR_ph = 1. 5%, - with reduced layer thicknesses by a factor k, which is smaller than 0.9, the color of the residual reflection differs under one  Angle of incidence arccos (k) of the color at 0 ° light incidence angle unreduced layer thicknesses of the layers (50-56) in the CIE xyz color system by not more than Δχ = 0.05, Ay = 0.05, preferably not more than Δχ = 0.03, Ay = 0.03, particularly preferred not more than Δχ = 0.02, Δν = 0.02,  with reduced layer thicknesses by a factor k which is smaller than 0.9, the color of the residual reflection under an angle of incidence arccos (k) no longer differs from the color at 0 ° light incidence angle with unreduced layer thicknesses of the layers (50-56) as AR_ph = 1.5% and wherein for at least one other pair the residual reflection and photopic reflectivity parameters are calculated and again at least one of the conditions is checked if the condition is not satisfied for the first pair, and a non-reduced layer sequence Layer thicknesses of a pair of antireflection coatings is selected, which satisfies at least one of the conditions, and wherein an antireflection coating (5) is deposited with this selected layer sequence on a substrate (3). 20. Method according to the preceding claim, characterized in that, among a plurality of pairs, a check as to the conditions of the  Difference of the color of the residual reflection at 0 ° angle of incidence or the difference of the photopic reflectivity at 0 ° angle of incidence occurs and among the tested pairs, the layer system for the deposition is selected in which the smallest difference of the color of the residual reflection at 0 ° light incidence angle and / or smallest difference of the photopic reflectivity at 0 ° light incident angle is present and then this layer system is deposited. 21. The method according to one of the two preceding claims, characterized in that the antireflection coating (5) is selected so that  the color of the residual reflection of the two antireflective coatings (5, 6) of a pair in the CIE xyz color system at an angle of incidence of 30 ° does not exceed Δχ = 0.05, Ay = 0.05 differs, or  - The color of the residual reflection of the two antireflection coatings (5, 6) of a pair in the CIE xyz color system at 45 ° angle of incidence by not more than Δχ = 0.05, Ay = 0.05 differs. 22. Method according to one of the three preceding claims, characterized in that at least one of the antireflection coatings of the pair of Antireflective coatings for which at least one of the parameters of color of residual reflection and photopic reflectivity is calculated, is selected such that at least one of the following conditions is met:  the ratio of the layer thickness of the uppermost layer of the antireflection coating 5 to the layer thickness of the third uppermost layer is in a range from 0.5 to 8.5, preferably in the range from 2 to 8, particularly preferably in the range from 3 to 8,  the ratio of the product of the layer thicknesses of the uppermost pair of layers to the product of the layer thicknesses of the second uppermost pair of layers is in one of the ranges from 8 to 22 or 60 to 140  the ratio of the layer thickness of the thickest layer under the layers of lower refractive index to the layer thickness of the thickest layer under the layers of higher refractive index is between 0.2 and 3, wherein a range from 1, 5 / F (n) to 2.5 / F (n), where F (n) is given by F (n) = (n-1) / (0.47) and n den Refractive index of the substrate denotes  the ratio of the standard deviation of the layer thicknesses of the layers to the layer thickness of the thickest layer of the antireflection coating is in a range of 0.25 to 0.45.