CH714955B1 - - Google Patents

Description

[0001] Anti-reflective layer systems are state of the art today and are used in many different ways. Areas of application include picture glazing, optical components such as lenses, e.g. for cameras. These applications are not exposed to heavy mechanical loads.

EP 2 492 251 B1 describes the production of anti-reflective layer systems for the watch glass industry, among others. In addition to the anti-reflection effect, the hardness of the AR system is also improved by the fact that a hard material layer made of Si3N4 with an admixture of aluminum is introduced as a high-index layer. Since watches and in particular so-called magnifying glasses for the date display, which are glued to the watch glass, are often mechanically stressed by scratching, the use of conventional anti-reflective coating systems does not make sense, as these can be completely removed due to the mechanical stress and the reflection of the substrate material. The hard AR system based on the development according to EP 2 492 251 B1 provides an anti-reflection system which is mechanically much more durable than conventional optical coatings.

Since sapphire is often used as a watch glass in the watchmaking industry, but anti-reflective coatings are generally much softer than sapphire, it would be desirable to be able to keep the anti-reflective effect as good as possible despite mechanical stress, ie that the residual reflection even after mechanical stress remains as low as possible. According to EP 2 492 251 B1, this is solved by the hard material layers, which bring about a high abrasion resistance of the layer system and thus only a slight change in the layer thicknesses.

[0004] Among the hard material layers, two-material systems traditionally play the main role. The oxides and nitrides of Cr, Si, Ti and Zr should be mentioned here in particular. 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, Al2O3, as described in DE 20106167, and yttrium-stabilized ZrO2. Glass ceramic substrates coated with carbon-doped silicon nitride are described in EP 1 453 770 B1.

[0005] WO 2009/010180 A1 and DE 10 2008 054 139 A1 describe aluminum-doped SiN or SiON layers with a scratch protection effect 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, the layers according to DE 10 2016 125 689 A1 being amorphous, while the layers according to DE 10 2014 104 798 A1 nano crystallites included.

Typically, scratch-resistant, anti-reflective coatings are deposited by sputtering. The antireflection coatings described in the prior art are designed for flat substrates. If the surface is not flat, the angle of the surface normal to the sputter source changes locally. This leads to a direction-dependent 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 also be deposited on non-planar substrates and still has good optical properties. The layer system is preferably also as insensitive as possible to partial abrasion of the uppermost layer. The abrasion can be checked with an abrasion test, e.g. B. the modified Bayer test, based on ASTM F735-11, but preferably tested with 2 kg corundum sand and 8000 cycles. This modified Bayer test is also described in the documents DE 10 2016 125 689 A1 and DE 10 2014 104 798 A1 mentioned above, the disclosure of which in this respect is also made the subject matter of the present application. Such a test typically removes more than ten nanometers of material from the top (last) layer of the anti-reflective coating. With typical layer thicknesses, this amount of material also corresponds to more than ten percent of the layer thickness. Experiments have shown that the modified Bayer test applied to coatings described in EP 1 453 770 B1, DE 10 2014 104 798 A1 and DE 10 2016 125 689 A1 brings about such a removal of material on the topmost layer. For example, the average layer thickness can be reduced from 100 nm to 80 nm using the Bayer test. Many scratches occur, but if the reflection spectrum is measured over a large area (e.g. on an area of 5 × 5 mm<2>), the abraded coating can be assigned a macroscopic resulting reflectivity or a macroscopic resulting residual reflection color that corresponds to the visual impression corresponds.

In order to make the change in the residual reflection as insensitive as possible to the vapor deposition angle, the invention is based on the idea of comparing or selecting layer sequences with one another when designing the layer system in such a way that the smallest possible change in optical parameters with regard to the color of the residual reflection, its angle dependence and especially the intensity of the residual reflection when the layer thicknesses of the layers are changed by an equal percentage.

In particular, the invention provides a transparent element comprising a transparent substrate and on this substrate a multilayer anti-reflective coating comprising at least six layers, layers with a high refractive index alternating with layers with a lower refractive index, and wherein the higher refractive index layers have a greater hardness than the lower refractive index layers, and wherein the topmost layer of the multilayer anti-reflective coating is a lower refractive index layer, and wherein the substrate has at least two surface areas that differ in terms of their inclination, wherein the anti-reflective coating covers the surface areas with different inclinations, and at least one of the following features applies to the anti-reflective coating on the surface areas: the colors of the residual reflection in each case at an angle of incidence of 0° on the surface areas differ from one another in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably by no more than Δx=0.02, Δy=0.02, the photopic reflectivities below 0° angle of incidence of the surface areas do not differ from each other by more than ΔR_ph=1.5%.

The difference is to be understood in each case as an amount. As a comparison, the terms "higher refractive index" and "lower refractive index" are to be understood relative to one another. A layer with a higher refractive index is therefore understood to be a layer whose refractive index is higher than a layer with a lower refractive index, without the absolute values of the refractive indices being quantified.

The integrated reflectivity is referred to as photopic reflectivity after it has been weighted with the sensitivity curve of the human eye with sufficient brightness (day vision). For the information given here, the standard illuminant D65 was used as the light source according to ISO standard 3664, a radiation distribution with a color temperature of 6504 Kelvin.

[0013] In particular, due to the more or less directional deposition process, the layer thickness of the anti-reflective coating can vary depending on the inclination of the different surface areas. The layer system is then designed in such a way that, with regard to the reflectivity and the color of the residual reflection, it is as little dependent as possible on a uniform reduction in the layer thicknesses of the individual layers. In particular, the anti-reflective coating can be designed in such a way that at least one of the following features applies: with reduced layer thicknesses by a factor k that is less than 0.9, the color of the residual reflection differs at a light incidence angle arccos(k) from the color at a light incidence angle of 0° with undiminished layer thicknesses of the layers (50 - 56) in the CIE xyz- color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably no more than Δx=0.02, Δy=0.02, with reduced layer thicknesses by a factor k that is less than 0.9, the color of the residual reflection at an angle of incidence arccos(k) differs from the color at an angle of incidence of 0° with undiminished layer thicknesses of the layers (50 - 56) by no more than ΔR_ph=1.5%. Since the reduction in layer thicknesses is caused by the slope of the respective surface, these two quantities are essentially proportional and can be used equivalently.

[0014] According to a preferred embodiment of the invention, the substrate has a flat central area and a bevel or, more generally, an edge area, with the antireflection coating covering both the central area and the bevel or the edge area, the layer thicknesses of the layers of the antireflection Coating on the bevel or the edge area are reduced compared to the layer thicknesses in the central area. 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 anti-reflection coating is produced using a directional coating process with the center region aligned with the coating source. The design of the anti-reflection coating according to the invention then results in no or at least no significant deviation in the color of the residual reflection or the reflectivity on the bevel or in the edge area. According to a development of the invention, an angle of at least 20° can be included between the surface normal of the bevel or the edge area and the surface normal of the central area. In particular, bevels with an angle of 30° to 80° are also contemplated, including the cases of bevels beveled at less than 45° and 60°. In general, it is favorable if, given a certain inclination of a surface area, for example the angle of a bevel, the antireflection coating is also optimized for this angle with regard to the color of the residual reflection and/or the photopic reflectivity. If, for example, a bevel is provided at a certain angle (e.g. 45°) to a flat central surface, the layer system can be optimized in such a way that the difference in the color values Δx, Δy is minimal or at least minimal for an equally large light incidence angle (e.g. also 45°). each is less than 0.05, preferably less than 0.03.

The central area can, for. B. be designed color neutral. If a design were now limited to the central area and left the effect on the bevel to chance, the bevel after coating could e.g. B. have an orange residual reflection color. Now, in a further embodiment, the design color of the central area and edge area (e.g. the chamfer) can differ and the central area e.g. B. neutral in color and the bevel can be made bluish.

Preferably, the layers of the anti-reflective coating are still selected for given refractive indices in terms of their thickness so that the color of the residual reflection at an angle of incidence between 30°-arccos(0.9)=4° and 30°+ arccos(0.9)=56°, with layer thicknesses reduced by 10%, differs from the color at an angle of incidence of 30° with undiminished layer thicknesses in the CIE xyz color system differs by no more than Δx=0.05, Δy=0.05, and/or the color of the residual reflection at an angle of incidence between 45°-arccos(0.9)=19° and 45°+ arccos(0.9)=71°, with layer thicknesses reduced by 10%, from the color at an angle of incidence of 45° with undiminished layer thicknesses im CIE xyz color system differs by no more than Δx=0.05, Δy=0.05. The anti-reflective coating can also be designed in such a way that the color of the residual reflection at an angle of incidence of 0° is uniformly reduced by at least 10% for all layer thicknesses In the CIE xyz color system, with an undiminished layer thickness of the top layer, they differed from the color at a light incidence angle of 0° (viewing angle in relation to the surface in the corresponding surface area) by no more than Δx=0.05, Δy=0.05, in particular by no more than Δx=0.03 , Δy=0.03, preferably no more than Δx=0.02, Δy=0.02.

[0017] Furthermore, the two above-mentioned features Δx=0.05, Δy=0.05 and/or a change in the photopic reflectivity by at most ΔR_ph=1.5% according to a development of the invention can also be achieved with a significantly greater reduction in the layer thicknesses of all layers, namely by 20% , or 30%, or even 40% can be achieved.

Such a reduction of all layer thicknesses continuously and up to a certain angular range occurs z. B. with lenses and domes, or curved windows. However, it is very difficult to obtain very good optical properties over a larger coating angle. In many cases it is therefore advantageous to limit the design to the coating angles that actually occur. For a flat component with a 45° chamfer, the design can e.g. B. be limited to the two coating angles 0° and 45°, while the viewing angle should be included in the design over the entire range from 0° to over 45°.

[0019] The reduction in all layer thicknesses is due to the fact that the same amount of material is deposited on the same cross section at the same time during coating on inclined surfaces. However, since the corresponding area of the surface to be coated is now arranged at an angle (e.g. a bevel of 45°), the actual surface is larger and consequently the layer thickness is lower. With a perfectly collimated/directional coating, the layer thickness would be reduced by a factor of the cosine of the tilt angle. Below 0°, 100% relative layer thickness is deposited as usual. Below 45° it would only be 71%. In typical sputtering processes, however, coatings are not completely aligned, but are deposited from a type of cloud, so that the layer thicknesses are typically somewhat greater. The following table shows measured layer thickness changes for a nitride layer during magnetron sputtering at different angles of the coated surface to the sputtering source, as well as changes in the refractive index: angle of incidence to photopic reflectivity below 0° angle of incidence 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 the average reflectivities at an angle of incidence of 30° and an angle of incidence of 0°, averaged in the wavelength range between 450 nm and 700 nm, is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%, - the absolute amount the difference in average reflectivity at 45° and 0° incidence, averaged over the wavelength range between 450 nm and 700 nm is less than 0.5% - the absolute value of the difference in the maxima of the reflectivities in the wavelength range between 450 nm and 700 nm at an angle of incidence of 30° and at an angle of incidence of 0° is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%, the absolute value of the difference in the maxima of the reflectivities in the wavelength range between 450 nm and 700 nm at an angle of incidence of 45° and at an angle of incidence of 0° is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%.

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

In a further development of this embodiment, the coating can even have 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 between the photopic reflectivity at an angle of incidence of 30° and the photopic reflectivity at an angle of incidence of 0° is less than 0.1%, the absolute value of the difference in the average reflectivity in the wavelength range between 450 nm and 700 nm at an angle of incidence of 30° to the average reflectivity in the wavelength range between 450 nm and 700 nm at an angle of incidence of 0° is less than 0.1%, the absolute value of the difference between the photopic reflectivity at an angle of incidence of 45° and the photopic reflectivity at an angle of incidence of 0° is less than 0.2%, the absolute value of the difference between the average reflectivity in the wavelength range between 450 nm and 700 nm at an angle of incidence of 45° and the average reflectivity in the wavelength range between 450 nm and 700 nm at an angle of incidence of 0° 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 another development of the invention, the layer system is designed in such a way that the surfaces with the different inclinations differ optically as little as possible from a given viewing angle of the transparent element. Accordingly, at least one further area of the surface should also be present, which is arranged at an angle to the area described above with the properties described above (e.g. a chamfer or curvature), and on which all layers with a different thickness are deposited during the coating process and which has at least one of the following features, preferably also several, in particular all features: the color of the residual reflection at an angle of incidence of 0° on the first area (main area described above) no longer differs from the color of another area (e.g. bevel) at a light incidence angle of 0° on this area in the CIE xyz color system as Δx=0.05, Δy=0.05, the color of the residual reflection at an angle of incidence of 0° on the first area differs from the color on another area with light incidence from the identical direction of incidence (in this case the angle of incidence is the angle of inclination of the two surface areas to one another) in the CIE xyz color system by no more than Δx =0.05, Δy=0.05, the color of the residual reflection at an angle of incidence of 0° on the first area differs from the color on a further area under all angles of incidence between 0° and the angle of inclination of the two surface areas to one another in the CIE xyz color system by no more than Δx=0.05, Δy=0.05 , the color of the residual reflection at an angle of incidence between 0° and the angle of inclination of the two surface areas to one another on the first area differs from the color on another area under light incidence from the identical direction in the CIE xyz color system by no more than Δx=0.05, Δy =0.05.

So-called targets can be defined for adapting the design. These are specifications of e.g. 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 be set with values e.g. For example, they can be specified as shortcuts such as "less than" or "as close as possible to". Colors are specified as "as close as possible to" the desired color location, reflectivities as "less than" a desired limit. Furthermore, deviations can then be penalized and the layer thicknesses of the design can be optimized with these penalizations in such a way that the lowest possible penalization is achieved. With weighting, deviations in various parameters can be included in the penalty to varying degrees. So e.g. For example, the residual reflection color or the reflectivity below 45° should be weighted less than below 0°. The weights are adjusted in the process to achieve desired coating characteristic results.

In particular, at least two, preferably several designs are defined, the layer thicknesses and layer materials being selected in such a way that they correspond to a coating process on different surface areas with different angles of inclination. Will e.g. If, for example, a main area of a surface and other areas arranged at angles are coated at the same time perpendicular to the main surface, with the layer thicknesses and possibly also the refractive indices of the different layers on the other areas being changed compared to the parameters for the main area, then the other layer designs should be flat reflect these changed coating conditions. Is there e.g. 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 (low and high refractive index L1 and H1) one could use Now describe the coating design for a first area of a surface (B1) as follows: B1: d1[L1] d2[H1] d3[L1] d4[H1] d5[L1] d6[H1] d7[L1].

In this case, [L1] designates a layer with a low refractive index, [H1] a layer with a high refractive index, d1-d7 are the respective layer thicknesses of these layers.

A design B2 with a different thickness and different refractive indices of the layers can now z. B. describe as follows B2: 0.71*d1[L2] 0.71*d2[H2] 0.71*d3[L2] 0.71*d4[H2] 0.71*d5[L2] 0.71*d6[H2] 0.71*d7[L2]. In design B2, all layers are reduced in thickness by 29%. In this example, the factor 0.71 corresponds approximately to 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. This factor can be increased up to 1 by certain 3-dimensional rotation systems of the substrate holders in coating machines. The determined factors can also differ for a range from layer material to layer material.

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

At least three, particularly preferably more, designs are particularly preferably defined, with at least two designs differing in all layer thicknesses (for simulating the coating at an angle, e.g. on a bevel) and at least one further design only in the uppermost one Layer experiences a reduced thickness simulating a simulation of abrasion. If the layer thickness change of all layers deposited at an angle α is now the same and this can be expressed with the factor w (which is typically between cos(α) and 1), the three designs can 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 includes defining the targets for each of these designs and adapting all designs at the same time (simultaneously) by changing the layer thicknesses d1, d2, . . . the designs still only differ by the same layer thickness differences . The targets for the different coating designs can differ and be weighted differently. So e.g. B. the residual reflection color or the reflectivity for the design in which the last layer is reduced in thickness by 40 nm weighted less important than for the design in which the last layer is not reduced in thickness.

[0030] An automatic adjustment method which is subjected to this procedure generally generates a number of different solutions which are optimal in different ways or optimal in terms of different parameters. So e.g. For example, one solution keeps the residual reflection color more constant while reducing the thickness of the last layer and another solution the more photopic reflectivity.

The method according to the invention for producing a transparent element can be summarized as follows: it is used for at least one pair of anti-reflective coatings (5, 6) which comprise at least six layers (50, 51, 52, 53, 54, 55, 56), layers with a high refractive index (51, 53, 55) alternating layers (50, 52, 54, 56) of lower refractive index, the layers (51, 53, 55) of higher refractive index having greater hardness than the layers (50, 52, 54, 56) of lower refractive index, and wherein the uppermost layer (56, 60) of the multilayer anti-reflective coating (5) is a layer with a lower refractive index, taking into account the refractive index of the substrate (3) at least one of the parameters Color of residual reflection and photopic reflectivity is calculated, with the two anti-reflective coatings differing in terms of the layer thicknesses of all layers, such that the layer thicknesses of all layers in an anti-reflective coating by a common factor, which has a value of at most 0.9, or between 0 and 0.9 , preferably in the range from 0.1 to 0.9, is reduced compared to the layer thickness of the other anti-reflective coating, and it is checked whether at least one of the conditions is met for both anti-reflective coatings: the color of the residual reflection at an angle of incidence of 0° with uniformly reduced layer thicknesses differs from the color at an angle of incidence of light of 0° with undiminished layer thicknesses in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, the photopic reflectivity at an angle of incidence of 0° with a uniformly reduced layer thickness of all layers (50, 51, 52, 53, 54, 55, 56) differs from the photopic reflectivity at an angle of incidence of 0° with undiminished layer thicknesses by no more than ΔR_ph=1.5%, with reduced layer thicknesses by a factor k that is less than 0.9, the color of the residual reflection differs at a light incidence angle arccos(k) from the color at a light incidence angle of 0° with undiminished layer thicknesses of the layers (50 - 56) in the CIE xyz- color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably no more than Δx=0.02, Δy=0.02, with reduced layer thicknesses by a factor k that is less than 0.9, the color of the residual reflection at an angle of incidence arccos(k) differs from the color at an angle of incidence of 0° with undiminished layer thicknesses of the layers (50 - 56) by no more than ΔR_ph=1.5%, and wherein the parameters of the color of the residual reflection and the photopic reflectivity are calculated for at least one further pair of anti-reflective coatings (5, 6) and at least one of the conditions is checked again if the condition for the first pair is not met and wherein a layer sequence with non-reduced layer thicknesses is selected from a pair of anti-reflection coatings, which fulfills at least one of the conditions, and wherein an anti-reflection coating with this selected layer sequence is deposited on a substrate.

According to one embodiment, the color of the residual reflection and the photopic reflectivity are determined for normal incidence of light, i.e. at an angle of incidence of light of 0°. Instead of just one pair of anti-reflective coatings (5, 6), a larger number of designs can also be brought into the simultaneous fitting process, e.g. B. Four designs where the second is reduced by 10% in the last layer thickness, 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 to continuously curved surfaces can also be obtained.

[0033] If one of the conditions is not met, the search continues according to the invention among the solutions found. Furthermore, it is typically necessary to optimize the weights and values of the targets so that fitting the designs generates solutions that meet or meet the desired conditions as well as possible. This search can also be continued in particular if a suitable pair of anti-reflective coatings (5, 6) has already been found, either in order to meet other conditions that have already been mentioned above, or also to find a layer system that is as optimal as possible . In general, a large number of pairs can be checked with regard to the above-mentioned conditions (namely the difference in the color of the residual reflection at an angle of incidence of 0° and/or the difference in the photopic reflectivity at an angle of incidence of 0°) and, among the pairs examined, the layer system for the Deposition are selected in which the smallest difference in the color of the residual reflection at 0 ° angle of incidence and / or the smallest difference in photopic reflectivity at 0 ° angle of incidence and then this layer system is deposited.

The selection of an anti-reflection layer system from a specific pair of anti-reflection coatings (5, 6) can be made depending on whether other conditions are present, namely in particular the features already listed above. In a further development of the invention, it is provided that the anti-reflective coating (5) is selected in such a way that the color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at an angle of incidence of 30° does not differ by more than Δx=0.05, Δy=0.05, or the color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at an angle of incidence of 45° does not differ by more than Δx=0.05, Δy=0.05.

The invention is particularly suitable for inorganic substrates. A preferred substrate is sapphire. This substrate is of particularly high quality, hard and transparent, so that the advantages of the invention, namely the provision of a high-quality, hard anti-reflection layer system which is very insensitive to abrasion, are particularly evident here. In addition to sapphire, 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 can also be used, for example glasses with the trade names NBK7, D263 or B270 (marketed by SCHOTT AG).

Silicon nitride (Si3N4), aluminum nitride (AlN), aluminum oxide (Al2O3) and oxynitrides (AlwSixNyOz) and mixtures of the materials mentioned are particularly suitable for the layers with a high refractive index. These materials not only have a high refractive index, but also great hardness. Among the nitrides, aluminum nitride and silicon nitride in particular should be mentioned as suitable layer materials. The materials can be doped or do not have to be in pure form. For example, aluminum nitride with a silicon content (e.g. between 0.05 and 0.25) or, conversely, silicon with an aluminum content (again, e.g. between 0.05 and 0.25) can be used as the material for the higher-index layers. At a wavelength of 550 nm, the layers with a lower refractive index have in particular a refractive index in the range from 1.3 to 1.6, preferably 1.45 to 1.5, and the layers with a 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.

According to another development of the invention, all of the above-mentioned features with regard to reflectivity and color location can also be met if the layer thicknesses of all layers are reduced even further, to a maximum of 0.8 times, particularly preferably a maximum of 0.7 times , particularly preferably at most 0.6 times the undiminished layer thicknesses.

The invention is particularly suitable for small substrates. The substrate preferably has an edge length or a diameter of less than 200 mm. An edge length or a diameter of less than 150 mm, in particular less than 100 mm, very particularly less than 50 mm, is preferred. Such a surface can be uniformly coated using a PVD process.

The substrate is preferably coated over the entire surface on at least one side, ie no overlying masks are used. The anti-reflective coating is preferably seamless due to the simultaneous coating of the areas, as shown in FIG. All layers of the anti-reflective coating are preferably coated in one operation, without the substrate having to be removed from the coating chamber in the meantime. In particular, it is also intended to coat a plurality of substrates at the same time.

Brief description of the figures:

Figure 1 shows a transparent element with a six-layer anti-reflection coating. Figure 2 shows a transparent element with an anti-reflective coating with a seven-layer anti-reflective coating. Figure 3 shows a transparent element with an anti-reflective coating on a non-planar surface. 4 schematically shows different forms of substrates. Fig. 5 shows color locations of the color of the residual reflectivity for different angles of incidence of light on a bevel and a main surface of a comparative example, Fig. 6 shows color locations of the color of the residual reflectivity for different angles of light incidence on a bevel and a main surface of an anti-reflective coating according to the invention. FIG. 7 shows three diagrams (a), (b), (c), which show the ratio of the layer thicknesses of the topmost to the third-topmost layer for a large number of anti-reflection coatings. In Fig. 8 two diagrams are shown in which the ratio of the product of the layer thicknesses of the two uppermost layers to the product of the layer thicknesses of the underlying pair of layers is plotted for two different substrates. FIG. 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 is shown for a large number of exemplary embodiments. 10 shows the ratio of the difference in the layer thickness of the thickest to the thinnest layer to the sum of the layer thicknesses of these layers for a large number of antireflection coatings on a sapphire substrate with a bevel angle of 30°. 11 shows two diagrams with values of the ratio of the standard deviation of the layer thicknesses to the layer thickness of the thickest layer.

Figure 1 shows two partial images (a) and (b). 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. A multilayer antireflection coating 5 is deposited on the substrate 3 . This has at least six layers 51, 52, 53, 54, 55, 56. The layers 51, 53, 55 have a high refractive index 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 identified 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 degree of hardness and durability of the antireflection coating 5 is brought about in particular by the layers 51, 53, 55 with a higher refractive index, which have a greater hardness than the low-index layers.

The layer 56 forms the top layer 60 of the anti-reflective coating and is a low refractive index layer. The transparent element 1 shown in partial image (b) differs from the element 1 according to partial image (a) only in that with the anti-reflective coating 6 the layer thicknesses of all layers 51 - 56 are each increased by a factor, correspondingly by the same percentage amount are reduced. There is a reduction Δd in the overall layer thickness. Since all layers are reduced in thickness by the same factor, the ratio of the reduction Δd to the total layer thickness D also applies to the layer thicknesses of the individual layers. The thickness of each of the layers 51-56 is therefore reduced by a factor Δd/D. Such a situation can arise if the antireflection coating 5 according to the invention, as shown in partial image (a), is partially deposited on a surface area inclined towards the coating source. The layer thicknesses of the layers 51 - 54 can now be selected according to the invention in such a way that, given the refractive indices of the layer materials and the substrate, when the layer thickness decreases according to the change between the two partial images (a), (b), the color of the residual reflection and/or the Reflectivity of the surface remains almost unchanged. In particular, the color of the residual reflection at an angle of incidence of 0° with a reduced layer thickness according to part (b) cannot deviate from the color with undiminished layer thicknesses measured in the CIE xyz color system by no more than Δx=0.05, Δy=0.05. Another, alternative or, in particular, additional criterion is the photopic reflectivity at different angles of incidence of light. The photopic reflectivity below 0° angle of incidence with reduced layer thicknesses according to sub-figure (b) can differ from the photopic reflectivity below 0° angle of incidence with undiminished layer thicknesses according to sub-figure (a) by no more than ΔR_ph=1.5%. These criteria can also be met with an antireflection coating 5 if the decrease in the layer thickness D is at least 0.1*d, ie at least 10%.

In general, the anti-reflection coating 5 can be designed in such a way that it simultaneously has all or most (many, preferably most, particularly preferably almost all, very particularly preferably all) of the following properties with an undiminished layer thickness: a) The anti-reflection Coating 5 has a residual reflection of a predefined color (e.g. in the CIE color space) at an angle of incidence of 0°, e.g. B. blue (e.g. x=0.20 +/- 0.05, y=0.20 +/- 0.05) or color neutral (e.g. x=0.30 +/- 0.05, y=0.32 +/- 0.05). b) The color of the residual reflection of the anti-reflective coating 5 at an angle of incidence of 30° differs from the color at an angle of incidence of 0° by no more than z. e.g. Δx=0.02, Δy=0.02. c) The color of the residual reflection of the anti-reflective coating 5 at an angle of incidence of 45° differs from the color at an angle of incidence of 0° by no more than z. Δx=0.05, Δy=0.05). d) The photopic reflectivity of the anti-reflective coating 5 (weighted with the sensitivity curve of the human eye) at an angle of incidence of 0° is less than 1.5% (e.g. also less than 2%, preferably less than 1.5%, especially preferably less than 1.0%, most preferably less than 0.8%). e) The photopic reflectivity of the antireflection coating 5 at an angle of incidence of 30° differs from the value at an angle of incidence of 0° by less than 0.2%, particularly preferably by less than 0.1%. f) The photopic reflectivity of the antireflection coating 5 at an angle of incidence of 45° differs from the value at an angle of incidence of 0° by less than 0.2%, particularly preferably by less than 0.1%. g) The average reflectivity of the anti-reflective coating 5 (averaged in the wavelength range between e.g. 450 nm and 700 nm) at a 0° angle of incidence is less than 1.5%, preferably less than 1.25%, particularly preferably less than 1 .0%. h) The average reflectivity of the antireflection coating 5 at an angle of incidence of 30° differs from the value at an angle of incidence of 0° by less than 0.5%, preferably by less than 0.2%, particularly preferably by less than 0.1%. i) The average reflectivity of the antireflection coating 5 at an angle of incidence of 45° differs from the value at an angle of incidence of 0° by less than less than 0.5%, preferably by less than 0.2%, particularly preferably by less than 0.1 %. j) The absolute reflectivity (maximum in the wavelength range between, for example, 450 nm and 700 nm) at an angle of incidence of 0° is less than 2%, preferably less than 1.5%, particularly preferably less than 1.0%. k) the absolute reflectivity at an angle of incidence of 30° differs from the value at an angle of incidence of 0° by less than 0.5%, preferably by less than 0.2%, particularly preferably by less than 0.1%. l) the absolute reflectivity at an angle of incidence of 45° differs from the value at an angle of incidence of 0° by less than 0.5%, preferably by less than 0.2%, particularly preferably by less than 0.1%.

If the layer thickness of the anti-reflective coating 5 according to the invention is reduced by 10%, preferably by 20%, particularly preferably by 30%, most preferably by 40%, or even by 50%, so that an anti-reflective coating 6 is obtained, such as 1, the following features can be present individually or in combination: m) The color of the residual reflection of the anti-reflection coating 6 with uniformly reduced layer thicknesses of all layers below an angle of incidence of 0° differs from the color of the anti-reflection Coating 5 with undiminished layer thicknesses of all layers below 0° angle of incidence by no more than Δx=0.05, Δy=0.05, preferably by no more than Δx=0.03, Δy=0.03, particularly preferably by no more than Δx=0.02, Δy=0.02, most preferably by no more than Δx=0.01, Δy=0.01. n) The color of the residual reflection at an angle of incidence of 30° of the anti-reflective coating 6 with uniformly reduced layer thicknesses of all layers differs from the color of the anti-reflective coating 5 with undiminished layer thicknesses below an angle of incidence of 30° by no more than Δx=0.05, Δy=0.05, preferably by no more than Δx=0.03, Δy=0.03, particularly preferably by no more than Δx=0.02, Δy=0.02, very particularly preferably by no more than Δx=0.01, Δy=0.01. o) The color of the residual reflection of the anti-reflective coating 6 with uniformly reduced layer thicknesses of all layers below an angle of incidence of 45° differs from the color of the anti-reflective coating 5 with undiminished layer thicknesses below an angle of incidence of 45° by no more than Δx=0.05, Δy=0.05, preferably by no more than Δx=0.03, Δy=0.03, particularly preferably by no more than Δx=0.02, Δy=0.02, very particularly preferably by no more than Δx=0.01, Δy=0.01. p) The photopic reflectivity of the anti-reflective coating 6 with uniformly reduced layer thicknesses of all layers below 0° angle of incidence differs from the color of the anti-reflective coating 5 with undiminished layer thicknesses below 0° angle of incidence by no more than ΔR_ph=1.5%, preferably by no more than ΔR_ph=1%, more preferably no more than ΔR_ph=0.5%, most preferably no more than ΔR_ph=0.25%.

In the example shown in FIG. 1, the anti-reflection coating 5 consists of a total of six layers, the bottom layer 51 being a high-index layer. Such a layer system is favorable if the refractive index of the substrate is significantly lower than the refractive index of the layers with a higher refractive index. On the other hand, in the case of a substrate with a refractive index greater than 1.65, it is advantageous to provide a layer 50 of lower refractive index 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-reflective coating 6, but with all layers by the same percentage or by the same factor are reduced in thickness.

In general, the embodiment of FIG. 2 is based on the fact that a substrate 3 is coated with an anti-reflective coating 5 according to the invention, the substrate 3 having a refractive index of more than 1.65, the bottom layer 50 having a layer with lower refractive index.

Preferably, the substrate 3 of this embodiment is a sapphire. The transparent element can then be, for example, a watch glass or a magnifying glass for a watch glass, such as is used to enlarge the date display. In addition to sapphire, other (single) crystals, such as CaF2, or glass ceramics or glasses, such as soda lime glass, borosilicate glass, aluminosilicate glass, lithium aluminosilicate glass, optical glasses can also be used as substrate material, for example glasses with the trade names NBK7, D263 or B270.

Figure 3 shows an important application for the invention. The layer system is particularly suitable for non-flat surfaces of substrates due to the layer thicknesses according to the invention. In general, it is provided that the anti-reflection coating 5 covers different surface areas 30, 32 of the substrate 3, which differ in terms of their inclination or in terms of the direction of their surface normals, with the layer thickness of the anti-reflective coating (and, as explained, the layer thicknesses of all layers of the coating) varies depending on the slope of the surface areas.

In a more or less directional deposition process, different layer thicknesses of the anti-reflection coating 5 then result depending on the local inclination of the surface. The substrate 3 can, as shown, in particular have an edge region whose inclination differs from a planar central region. A typical case of such a surface area 32 is a chamfer 31. According to a preferred embodiment of the invention, without limitation to the example shown, it is generally provided that the anti-reflective coating 5 covers both the central area as the first surface area 30 and the chamfer 31 or more generally covers an edge area as a further surface area 32, the layer thicknesses of the layers of the antireflection coating 5 on the bevel 31 or the edge area being reduced compared to the layer thicknesses in the middle area. Accordingly, the total layer thickness d′ of the antireflection coating 5 in the edge area is also less than the layer thickness d in the flat central area.

The property of a layer system according to the invention of being tolerant of thickness fluctuations with regard to the optical properties is particularly advantageous if there are clear angles between the surface normals of different coated surface areas. Therefore, in a further development of this embodiment of the invention, an angle of at least 20° is included between the surface normal of the bevel 31 or the edge area and the surface normal of the central area.

If, in a directional deposition process, such as in particular sputtering, deposition occurs on a surface that is not oriented perpendicularly to the beam direction, i.e. on the bevel 31 in the example shown in FIG Degree of oxidation) of the layer compared to a surface oriented perpendicular to the beam direction. The changed density is then typically accompanied by a somewhat changed refractive index, despite a similar or unchanged composition of the layer material. This effect can already be taken into account when designing 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 anti-reflection coating have a refractive index that varies with the thickness of the layer and/or the inclination of the surface. The refractive index is usually lower, but depending on the composition and deposition process, the refractive index can also be higher with a smaller layer thickness.

4 shows three examples of further substrates 3 with surface regions 30, 32 of different inclinations. The various surface areas are generally subdivided into main and secondary areas, with the scale being the proportion of the total area. The area proportion of the secondary area is less than 50%, preferably less than 30%, in particular less than 10%, or even less than 5%. In examples (a), (b), (c), the inclination of the main surfaces lies parallel to the opposite side surface of the generally disc-shaped substrate 3. As in example (a), a surface area 32 can also be curved, in particular dome-shaped. The inclination in this surface area 32 thus changes continuously. However, a substrate that is curved overall, for example in the form of a lens, can also be provided. Edge areas as surface areas 32 with an inclination deviating from the main surface can be designed as a chamfer or flat surface, or else curved, as also illustrated in example (a).

In example (b), the surface area 30 is divided into several terraced areas. The transitions between the height steps form surface areas 32 with a deviating inclination, which in turn can be constant or can vary continuously in the form of a curvature.

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

[0055] In general, it is advantageous to weight the aspects of color equality and anti-reflection coating differently in the case of a subdivision into main and secondary areas. Good anti-reflective coating is particularly important for the main surface. 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 major surface also defines the color of the residual reflection perceptible to the viewer. This is preferably neutral in color, but can also be bluish, for example. In the case of the surface area with a smaller area, i.e. the secondary area, the color of the residual reflection plays a greater role. A deviation from the color of the main surface is more likely to be perceived as conspicuous than a locally larger reflection. According to one embodiment of the invention, the anti-reflective coating can generally be designed in such a way that the average or mean reflectivity on the secondary surface is higher by a factor of 2 to 5 than on the main surface, but the photopic reflectivity is still lower than that of the uncoated substrate. With sapphire as the substrate, the average reflectivity is 7.5% to 8% at 0° incidence of light, ie perpendicular incidence of light, and 30% to 50% at 45° incidence of light. In the embodiments described so far, the layer system is optimized with regard to certain light incidence directions at the same angle in relation to the respective normals of the surface areas. In other words, the layer system is designed in such a way that differently inclined surface areas each have colors of the residual reflection that are as similar as possible and/or reflectivities that are as low as possible, for example with perpendicular incidence of light. However, under illumination with a real light source, there is a case where the incident angle of the light varies depending on the inclination of the surface area. According to the invention, it is therefore also provided in particular that the anti-reflection coating 5 has at least one of the following features: the colors of the residual reflection of the surface areas (30, 32) of different inclination differ from one another in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably no more as Δx=0.02, Δy=0.02 when the transparent element (1) is irradiated with light which strikes one of the surface areas perpendicularly, the photopic reflectivities of the surface areas of different inclination differ from one another by no more than ΔR_ph=1.5% when the transparent element (1) is irradiated with light which strikes one of the surface areas perpendicularly. The inclination is again clearly different, so that there is an angle of at least 20°, preferably at least 30°, between the normals of the surface areas.

The invention is not limited to the exemplary embodiments, but can be varied in many ways within the scope of the subject matter of the claims. Different exemplary embodiments can also be combined with one another. An anti-reflection coating can thus be applied to both sides of a disc-shaped substrate. The anti-reflection coatings can then also have different colors of the residual reflection. Furthermore, the invention is not limited to six- or seven-layer coatings, as shown by way of example in FIGS. 1 and 2 . Even more layers can be provided, e.g. B. 9 layers in Example 2 described below. However, it is generally preferred that the antireflection coating 5 has a maximum of twenty, particularly preferably a maximum of fifteen layers, in order to keep the production costs within limits and to maintain the abrasion resistance.

Exemplary embodiments of layer systems according to the invention are described below.

Example 1 is a theoretical or calculated example of an anti-reflective coating (7 layers) on sapphire: The adaptation process leads, among other things, to the following theoretical solution for a system that is supposed to be neutral in color and anti-reflective on the main surface 1, which should also remains color neutral and low reflective at viewing angles, and retains this property when the top layer is damaged by abrasion. There is also a second surface which is at an angle of 45° to the first surface and if this second surface is viewed from a direction which is normal to the first surface +/-10° then this second surface also appears color-neutral and less reflective than uncoated. 1 low 34.3 nm 2 high 12.5 nm 3 low 174.9 nm 4 high 15.2 nm 5 low 40.2 nm 6 high 142.6 nm 7 low 85.6 nm air 1 color point target x 0.333 color point target y 0.333 color point CIE x viewed under 0° 0.327 color point CIE y viewed at 0° 0.333 color locus deviation x viewed from target at 0° 0.006 color locus deviation y viewed from target at 0° 0.000 color locus CIE x viewed at 20° 0.334 color locus CIE y viewed at 20° 0.333 color locus deviation x from target viewed at 20° 0.001 color locus deviation y from target viewed at 20° 0.000 photopic reflectivity target < 1.00% photopic reflectivity viewed at 0° 0.82% photopic reflectivity viewed at 20° 0.87% color locus CIE x viewed at 0° 0.318 color locus CIE y viewed under 0° 0.293 color point deviation x viewed from target under 0° 0.015 color point deviation y viewed from target under 0° 0.040 photopic reflectivity viewed under 0° 1.27% color point target x 0.333 color point target y 0.333 color point CIE x viewed at 45° 0.334 color point CIE y viewed at 45° 0.330 color point deviation x viewed from target at 45° 0.001 color point deviation y viewed from target at 45° 0.003 color point CIE x viewed at 35° 0.337 color point CIE y viewed at 35 ° 0.373 Color point deviation x viewed from target at 35° 0.004 Color point deviation y viewed from target at 35° 0.040 Color point CIE x viewed at 55° 0.342 Color point CIE y viewed at 55° 0.309 Color point deviation x from target viewed at 55° 0.009 color point deviation y from target viewed at 55° 0.024 photopic reflectivity target < 4.00% photopic reflectivity viewed at 0° 2.98%

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

Example 2 is an anti-reflective (AR) design on sapphire (9 layers).

The tables below show values from the theoretical simulation of the design as well as measured values on the deposited layer system. This is a coating that should be neutral in color but slightly bluish, reflects little and shows these properties in a large viewing angle range from 0° to 45°. Furthermore, these properties are retained when the top layer is damaged by a harsh abrasion test. In addition, the substrate includes a 60° bevel, which is also color-neutral and less reflective when viewed normal to the main surface +/- 10° (i.e. even below 60°+/- 10°). The modified Bayer test described above was used as the abrasion test, in which 2 kg corundum sand (Al2O3) rubs 8000 times at 150 cycles/minute due to its inertia over a 100 mm moving substrate.

For the most part, the many challenges are met well in practical example, thereby showing that the appropriate design is a suitable implementation of the invention. It is true that the exact values on the small bevel could not be measured exactly. However, a visual comparative assessment was carried out under a microscope: the visual impression is actually that the bevel is significantly more color-neutral and less reflective than with a standard AR coating. Color point design target x 0.295 Color point design target y 0.300 Color point CIE x viewed at 0° 0.294 0.262 Color point CIE y viewed at 0° 0.293 0.285 Color point deviation x from target viewed at 0° 0.001 0.033 Color point deviation y from target viewed at 0° 0.007 0.015 color point CIE x viewed at 30° 0.290 0.263 color point CIE y viewed at 30° 0.289 0.280 color point deviation x viewed from target at 30° 0.005 0.032 color point deviation y from target viewed at 30° 0.011 0.020 color point CIE x viewed at 45 ° 0.311 0.314 color point CIE y viewed at 45° 0.319 0.319 color point deviation x viewed from target at 45° 0.016 0.019 color point deviation y viewed from target at 45° 0.019 0.019 photopic reflectivity target < 1.5% photopic reflectivity viewed at 0° 1.22% 1.52% photopic reflectivity viewed at 30° 1.15% 1.13% photopic reflectivity viewed at 45° 1.63% 1.31% color point CIE x viewed at 0° 0.267 color point CIE y viewed at 0 ° 0.285 color locus deviation x viewed from target at 0° 0.028 color locus deviation y viewed from target at 0° 0.015 color locus CIE x viewed at 30° 0.290 color locus CIE y viewed at 30° 0.291 color locus deviation x from target viewed at 30° 0.005 Color point deviation y viewed from target at 30° 0.009 Color point CIE x viewed at 45° 0.360 Color point CIE y viewed at 45° 0.321 Color point deviation x viewed from target at 45° 0.065 Color point deviation y from target viewed at 45° 0.021 photopic reflectivity viewed at 0° 0.68% photopic reflectivity viewed at 30° 0.77% photopic reflectivity viewed at 45° 1.45% color point CIE x viewed at 0° 0.266 color point CIE y viewed at 0° 0.281 color point deviation x from target viewed at 0° 0.029 Color point deviation y viewed from the target at 0° 0.019 Color point CIE x viewed at 30° 0.325 Color point CIE y viewed at 30° 0.301 Color point deviation x from the target betrac htet under 30° 0.030 color point deviation y viewed from the target under 30° 0.001 color point CIE x viewed under 45° 0.402 color point CIE y viewed under 45° 0.317 color point deviation x viewed from the target under 45° 0.107 color point deviation y viewed from the target at 45° 0.017 photopic reflectivity viewed at 0° 0.67% photopic reflectivity viewed at 30° 0.91% photopic reflectivity viewed at 45° 1.82% color point CIE x viewed at 0° 0.256 color point CIE y viewed at 0° 0.296 color point deviation x from target viewed at 0° 0.039 color locus deviation y viewed from target viewed at 0° 0.004 color locus CIE x viewed at 30° 0.240 color locus CIE y viewed at 30° 0.291 color locus deviation x viewed from target at 30° 0.055 color locus deviation y viewed from target under 30° 0.009 color point CIE x viewed under 45° 0.276 color point CIE y viewed under 45° 0.324 color point deviation x viewed from the target under 45° 0.019 color point deviation y from target viewed at 45° 0.024 photopic reflectivity viewed at 0° 1.59% photopic reflectivity viewed at 30° 1.35% photopic reflectivity viewed at 45° 1.79% color point design target x 0.295 color point design target y 0.300 color point CIE x viewed at 60° 0.305 color point CIE y viewed at 60° 0.274 color locus deviation x viewed from target at 60° 0.010 color locus deviation y viewed from target at 60° 0.026 color locus CIE x viewed at 50° 0.282 color locus CIE y viewed at 50° 0.253 color locus deviation x from Target viewed from 50° 0.013 color point deviation y from target viewed from 50° 0.047 color point CIE x viewed from 70° 0.323 color point CIE v viewed from 70° 0.302 color point deviation x from target viewed from 70° 0.028 color point deviation y from target viewed at 70° 0.002

5 and 6 show, as color locus diagrams in the CIE 1931 color space, two examples for color values of the residual reflection at different light incidence angles for coatings on sapphire substrates with a bevel. The limitations of the color space are drawn in the diagrams. Both layer systems were optimized for a target color locus on the main surface of x=0.31, y=0.31.

In both examples, the bevel is angled at 55° in relation to the main surface. The anti-reflective coating covers the main surface and the bevel. As shown in FIG. 3, a layer thickness reduction on the bevel, caused by a directional coating process, was assumed for the calculation of the optical properties.

The layer thicknesses of the example in FIG. 5 on the main surface are in the order from the bottom to the top layer: 34.8 nm / 27.6 nm / 38 nm / 140.4 nm / 91.6 nm. The angling results in the following reduced layer thicknesses on the bevel: 20nm / 15.9nm / 21.8nm / 80.5nm / 52.5nm.

In the example shown in FIG. 6, the layer thicknesses, increasing from the bottom to the top layer on the main surface, are: 44.8nm / 19.9nm / 62.5nm / 28.9nm / 30.9nm / 48.2nm / 20.4nm / 159.8nm / 76.37nm.

The corresponding layer thicknesses on the bevel are: 44.8nm / 19.9nm / 62.5nm / 28.9nm / 30.9nm / 48.2nm / 20.4nm / 159.8nm / 76.37nm.

The color values of the main area are plotted as points in the diagrams of FIGS. 5 and 6, and the values of the bevel are plotted as open triangles. The y color values are also entered in the diagrams.

As can be seen by comparing the diagrams, with an anti-reflection coating according to the invention the change in the color values between the bevel and the main surface is small overall, and there is hardly any change in the color as a function of the angle of incidence of the light. All values are close together in the color locus diagram of FIG. 6, while in the comparative example they are widened approximately along a line.

The values are detailed below in the two tables. In the table, the information EW denotes the angle of incidence, R the reduction in the layer thickness of the top layer and R_ph the photopic reflectivity Example 1 (Fig. 5) Color not optimized for angle, abrasion and bevel EW R [nm] R_ph [%] xy Δ (xy) Comment Coating on major surface below 0° 0° 0 0.72 0.31 0 0.31 0 0.030 0°, 100% layer (new): perfect 15° 0 0.73 0.31 5 0.31 2 0.025 30° 0 0.87 0.32 6 0.33 5 0.006 strong color deviations at different viewing angles 45° 0 1.67 0.32 5 0.36 8 0.038 60° 0 5.27 0.31 2 0.35 6 0.031 0° 10 0.97 0.34 4 0.33 8 0.015 strong color deviations after abrasion 15° 10 z1.03 0.34 6 0.34 6 0.021 strong color deviations after abrasion 30° 10 1.30 0.34 3 0 .37 0 0.041 strong color deviations after abrasion 45° 10 2.28 0.32 7 0.37 9 0.048 strong color deviations after abrasion 60° 10 6.11 0.31 1 0.35 2 0.029 Coating on bevel under 55° 0° 0 7.64 0.46 0 0.45 1 0.176 very strong color deviations from different viewing angles n : bright/le bright/ brilliant orange 15° 0 8.03 0.45 2 0.44 8 0.169 30° 0 9.23 0.43 2 0.43 9 0.148 45° 0 11.67 0.40 1 0.41 9 0.112 60 ° 0 17.16 0.36 2 0.38 7 0.064 0° 10 7.78 0.41 8 0.43 1 0.133 very strong color deviations at different viewing angles n after abrasion 15° 10 8.08 0.41 2 0, 42 7 .126 30° 10 9.05 .39 4 .41 5 .105 45° 10 11.10 .36 8 .39 4 .073 60° 10 16.12 .34 0 .36 6 .036 Example 2 (Fig. 6) Color optimized for angle, abrasion and chamfer EW R [nm] R_ph [%] xy Δ(xy) Comment Coating on main surface below 0° 0° 0 1.416 0.30 2 0.30 8 0.008 15° 0 1.460 0, 30 1 0.30 6 0.010 30° 0 1.701 0.29 8 0.30 5 0.013 45° 0 2.656 0.30 9 0.31 5 0.005 60° 0 6.548 0.33 1 0.32 4 0.025 0° 10 2.464 0.28 8 0.28 0 0.037 15° 10 2.516 0.28 7 0.27 7 0.041 30° 10 2.788 0.28 8 0.27 7 0.040 45° 10 3.828 0.30 5 0.29 4 0.016 60° 10 7.934 0.33 1 0.31 5 0.022 Coating on bevel under 55° 0° 0 7.716 0.29 8 0.35 6 0.048 15° 0 7.592 0.29 3 0.34 5 0.039 30° 0 7.368 0.28 4 0.31 6 0.027 45° 0 7.816 0.28 7 0.29 0 0.031 60° 0 11.497 0.30 7 0.29 1 0.020 0° 10 8.657 0.29 0 0.33 8 0.034 15° 10 8.491 0 .28 6 0.32 8 0.030 30° 10 8.173 0.28 0 0.30 4 0.030 45° 10 8.542 0.28 6 0.28 3 0.036 60° 10 12.189 0.30 8 0.28 9 0.021

[0070] Further features of antireflection coatings according to the invention are discussed below 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 from 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. According to one embodiment, a characteristic of suitable coatings is the ratio of the layer thicknesses of the top layer to the third top layer, these being generally the top layer with a lower refractive index and the second top layer with a lower refractive index. According to one embodiment of the invention, the ratio of the layer thickness of the top layer to the layer thickness of the third top 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. FIG. 7 shows three diagrams (a), (b), (c), in which the above-mentioned ratio is shown for a large number of optimized anti-reflection coatings. The ratio is plotted on the ordinate of the diagrams, each point in the diagrams represents an anti-reflection coating. Graph (a) plots the ratio for coatings required for a sapphire substrate having 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 are optimized for a borosilicate glass and a facet angled under 55°. The examples of chart (c) are optimized coatings for a sapphire substrate with a 30° angled facet. As can be seen, for all three configurations the ratios range from 0.5 to 8, with only one example having a very thick third top layer in chart (b) having a ratio below 2.

According to another embodiment of the invention, it is provided that, in particular when the second surface area is inclined relative 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 plies in one of the ranges of 8 to 22 or 60 to 140. In other words, the layer thickness here is in the range from 8 to 140, with a range between 22 and 60 being excluded. In the example of Figure 1, the above ratio V would be formed by (layer thickness ply 56×layer thickness ply 55)/(layer thickness ply 54×layer thickness ply 53).

8 shows two diagrams (a), (b) in which the ratio is plotted on the ordinate for a large number of exemplary embodiments. The anti-reflection coatings correspond to those of diagrams (a) and (b) of FIG anti-reflective coatings optimized on a borosilicate glass substrate with a facet angled at 55°. If the features explained above are used as secondary conditions, the effort involved in optimizing the layer systems can also be correspondingly reduced, since the number of possibilities and thus also the calculation effort is significantly reduced. Accordingly, a further development of the method provides that at least one of the anti-reflective coatings from the pair of anti-reflective coatings for which at least one of the parameters color of the 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 top layer of the anti-reflection coating 5 to the layer thickness of the third top 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 top pair of layers to the product of the layer thicknesses of the next to top pair of layers is in one of the ranges of 8 to 22 or 60 to 140.

The ratio of the thickest high-index and low-index layers also has an influence on the optical properties in relation to the invariance when coating differently inclined surfaces. 9 shows two diagrams in this regard, in which the ratio of the layer thickness of the thickest, low-index layer to the layer thickness of the lowest, high-index layer is shown for a large number of exemplary embodiments. Diagram (a) shows the relationship for a variety of embodiments on a sapphire substrate, where the embodiments are optimized for either 30° or 55° facets. Chart (b) shows the ratio values for anti-reflective coatings optimized for a borosilicate glass substrate with a 55° bevel. It can be seen that in both cases there is a range in the values in which there are no coatings with favorable properties. It cannot be ruled out that there are also suitable coatings in these areas, but these are obviously at least less common. It can also be seen that the range depends on the refractive index of the substrate. In the case of borosilicate glass with a refractive index of 1.47 at a light wavelength of 550 nm, the range is around the value two, while in the case of the sapphire substrate with a refractive index of around 1.77, the range is around the value two. The dependency can be represented well with a factor (n-1)/(nBoro-1), where nBoroden denotes the refractive index of the borosilicate glass, ie at 550 nm, a value of 1.47. An advantageous feature of anti-reflective coatings according to the invention can thus be defined as follows: The ratio of the layer thickness of the thickest layer among the layers with a lower refractive index to the layer thickness of the thickest layer among the layers with a higher refractive index is between 0.2 and 3, with 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)/(nBoro -1), or with the refractive index of borosilicate glass F(n)=(n-1)/(0.47). Here too, depending on the refractive index of the substrate, a corresponding secondary condition can be created for the method for producing a transparent element in order to restrict the selection of possible designs.

is shown for a variety of anti-reflective coatings on a sapphire substrate with a bevel angle of 30 ° the ratio of the difference in layer thickness of the thickest to the thinnest layer to the sum of the layer thicknesses of these layers. The points result according to the relationship (dmax-dmin)/(dmax+dmin), where dmax denotes the maximum layer thickness of all layers and dmin denotes the minimum layer thickness of all layers of a suitable anti-reflection coating. The values of this ratio are similar for the other systems discussed here as examples, i.e. anti-reflective coatings on sapphire and borosilicate glass with a bevel angle of 55° each. Without being restricted to the exemplary embodiments shown, according to one embodiment of the invention the value of this ratio (dmax-dmin)/(dmax+dmin) is at least 0.65.

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

Without being restricted to the exemplary embodiments, it is therefore provided according to one embodiment of the invention that 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 from 0.25 to 0.45. A corresponding secondary condition can also be formulated here in order to simplify the selection of possible suitable designs.

Three exemplary embodiments from the set of anti-reflection coatings whose values are shown in FIGS. 7 to 11 are listed below.

An anti-reflection coating on a sapphire substrate with a bevel angle of 55° has the following layer thicknesses, with the details (h) and (I) denoting high and low refractive 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) / 13.45nm (I) / 237.9nm (h) / 94.3nm (I).

An anti-reflection coating on a sapphire substrate with a bevel angle of 30° has the following layer thicknesses, with the details (h) and (I) denoting high and low refractive 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, 4nm (I).

An anti-reflection coating on a borosilicate glass substrate with a bevel angle of 55° has the following layer thicknesses, with the details (h) and (I) denoting high and low refractive index layers, respectively: Substrate / 268.7nm (h) / 24.7nm (I) / 45.3nm (h) / 49.6nm (I) / 30.1nm (h) / 154.3nm (I).

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

Claims (22)

1. A method for producing a transparent element (1), comprising a transparent substrate (3) with at least two surface areas (30, 32) which differ in terms of their inclination and on this substrate (3) deposited anti-reflection coatings (5, 6 ), with the steps: - It is for at least one pair of anti-reflective coatings (5, 6), which include at least six layers (50, 51, 52, 53, 54, 55, 56), wherein layers (51, 53, 55) with high Alternating refractive index with layers (50, 52, 54, 56) with lower refractive index, the layers (51, 53, 55) with higher refractive index having a greater hardness than the layers (50, 52, 54, 56) with lower refractive index, and wherein the top layer (56, 60) of the multilayer anti-reflective coating (5) is a layer with a lower refractive index, taking into account the refractive index of the substrate (3) at least one of the parameters – Color of the residual reflection and - photopic reflectivity is calculated, with the two anti-reflective coatings (5, 6) differing in terms of the layer thicknesses of the top layer (56, 60) or all layers, such that the layer thicknesses of the top layer (60) or all layers in an anti-reflective 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 anti-reflective coating (5), and it is checked whether for both anti-reflective coatings (5, 6) at least one of the conditions is met: - A color of the residual reflection at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32) with uniformly reduced layer thicknesses of all layers differs from the color at an angle of light incidence of 0° with undiminished layer thicknesses in the CIE xyz color system by no more than Δx= 0.05, Δy=0.05, - A photopic reflectivity below 0° angle of incidence on the surface in the corresponding surface area (30, 32) with a uniformly reduced layer thickness of all layers (50, 51, 52, 53, 54, 55, 56) differs from the photopic reflectivity below 0° Angle of incidence with undiminished layer thicknesses by no more than ΔR_ph=1.5%, - With reduced layer thicknesses by a factor k that is less than 0.9, the color of the residual reflection differs at a light incidence angle arccos(k) from the color at 0° light incidence angle on the surface in the corresponding surface area (30, 32). undiminished layer thicknesses of the layers (50-56) in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably no more than Δx=0.02, Δy=0.02 , - With reduced layer thicknesses by a factor k that is less than 0.9, the color of the residual reflection differs at an angle of incidence arccos(k) from the color at 0° light incidence angle on the surface in the corresponding surface area (30, 32). undiminished layer thicknesses of the layers (50 - 56) by no more than ΔR_ph=1.5% and the parameters of the color of the residual reflection and the photopic reflectivity are calculated for at least one further pair and at least one of the conditions is checked again if for the first pair the Condition is not met, and wherein a layer sequence with non-reduced layer thicknesses is selected from a pair of anti-reflection coatings, which meets at least one of the conditions, and wherein an anti-reflection coating (5) with this selected layer sequence is deposited on a substrate (3). will. 2. The method according to claim 1, characterized in that, among a plurality of pairs, a check is made with regard to the conditions of the difference in the color of the residual reflection below 0° angle of incidence on the surface in the corresponding surface area (30, 32) or the difference in photopic reflectivity below 0° angle of incidence on the surface in the corresponding surface area (30, 32) and the layer system for the deposition is selected from the pairs examined, in which the smallest difference in the color of the residual reflection under 0° light incidence angle and / or the smallest difference in the photopic Reflectivity below 0 ° light incidence angle is present and then this layer system is deposited. 3. The method according to any one of claims 1 or 2, characterized in that the anti-reflective coating (5) is selected so that – the color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at an angle of incidence of 30° does not differ by more than Δx=0.05, Δy=0.05, or - The color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at an angle of incidence of 45° does not differ by more than Δx=0.05, Δy=0.05. 4. The method according to any one of claims 1 to 3, characterized in that at least one of the anti-reflective coatings from the pair of anti-reflective coatings for which at least one of the parameters color of the residual reflection and photopic reflectivity is calculated is selected such that at least one of the following conditions are met: - The ratio of the layer thickness of the top layer (56) of the anti-reflective coating (5) to the layer thickness of the third top layer is in a range from 0.5 to 8.5, preferably in the range from 2 to 8, particularly preferably in the range of 3 till 8, - the ratio of the product of the layer thicknesses of the top pair of layers to the product of the layer thicknesses of the second top pair of layers is in one of the ranges of 8 to 22 or 60 to 140 - the ratio of the layer thickness of the thickest layer among the layers with a lower refractive index to the layer thickness of the thickest layer among the layers with a higher refractive index is between 0.2 and 3, with a range from 1.5/F(n) to 2.5/ F(n) is excluded, where F(n) is given by F(n)=(n-1)/(0.47) and n denotes the refractive index of the substrate, - the ratio of the standard deviation of the layer thicknesses of all layers to the layer thickness of the thickest layer of the anti-reflective coating is in a range from 0.25 to 0.45. 5. Transparent element (1), produced by a method according to any one of claims 1 to 4, comprising - the transparent substrate (3) and on this substrate (3) - The multi-layer anti-reflective coating (5), which comprises at least six layers, wherein layers (51, 53, 55) with a high refractive index alternate with layers (50, 52, 54, 56) with a lower refractive index, and wherein - The layers (51, 53, 55) with a higher refractive index have a greater hardness than the layers (50, 52, 54, 56) with a lower refractive index, and wherein the top layer (60) of the multilayer anti-reflective coating (5) has a is layer with lower refractive index, and where - The substrate (3) has at least two surface areas (30, 32) which differ in terms of their inclination, wherein - The anti-reflection coating (5) covers the surface areas (30, 32) with different inclinations, and at least one of the following features applies to the anti-reflection coating (5) on the surface areas (30, 32): - The colors of the residual reflection each at an angle of incidence of 0° on the surface areas (30, 32) differ from one another in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, more preferably by no more than Δx=0.02, Δy=0.02, - The photopic reflectivities at 0° angle of incidence of the surface areas (30, 32) differ from each other by no more than ΔR_ph=1.5%. 6. Transparent element (1) according to claim 5, characterized in that the anti-reflection coating (5) has at least one of the following features: - The colors of the residual reflection of the surface areas (30, 32) of different inclination differ from one another in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably not more than Δx=0.02, Δy=0.02 when the transparent element (1) is irradiated with light which strikes one of the surface areas (30, 32) perpendicularly, - The photopic reflectivities of the surface areas (30, 32) of different inclination differ from each other by no more than ΔR_ph=1.5% when the transparent element (1) is irradiated with light which strikes one of the surface areas (30, 32) perpendicularly, there being an angle of at least 20°, preferably at least 30°, between the normals of the surface areas (30, 32). 7. Transparent element (1) according to one of claims 5 or 6, characterized in that the layer thickness of the anti-reflection coating (5) varies depending on the inclination of the surface areas (30, 32). 8. Transparent element (1) according to claim 7, characterized in that the anti-reflection coatings (5, 6) have at least one of the following features: - With reduced layer thicknesses of the top layer (60) or all layers of the anti-reflective coating (6) by a common factor k, which is less than 0.9, the color of the residual reflection differs from the color at a light incidence angle arccos(k). below 0° light incidence angle on the surface in the corresponding surface area (30, 32) with undiminished layer thicknesses of the layers (50 - 56) of the anti-reflective coating (5) in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably no more than Δx=0.02, Δy=0.02, - With reduced layer thicknesses of the top layer (60) or all layers of the anti-reflective coating (6) by a common factor k, which is less than 0.9, the color of the residual reflection differs from the color at an angle of incidence arccos(k). below 0° light incidence angle on the surface in the corresponding surface area (30, 32) with undiminished layer thicknesses of the antireflective coating (5) of the layers (50 - 56) by no more than ΔR_ph=1.5%. 9. Transparent element (1) according to claim 8, characterized in that the substrate (3) has a flat central area (30) and a bevel (31) or an edge area (32), and the anti-reflection coating (5) covers both the central area (30) and the chamfer (31) or the edge area (32), and the layer thicknesses of the layers (50-56) of the anti-reflective coating (5) on the chamfer (31) or the edge area ( 32) are reduced compared to the layer thicknesses in the middle area (30). 10. Transparent element (1) according to claim 9, wherein an angle of at least 20° is included between the surface normal of the bevel (31) or the edge area (32) and the surface normal of the central area (30). 11. Transparent element (1) according to one of claims 5 to 10, characterized in that at least some of the layers (50-56) of the antireflection coating (5) have a refractive index that varies with the thickness of the layer or the inclination of the surface . 12. Transparent element (1) according to any one of claims 5 to 11, characterized in that the layers (51-56) are selected in terms of their thickness for given refractive indices such that - the color of the residual reflection at an angle of incidence on the surface in the corresponding surface area (30, 32) lying between 30°-arccos(0.9)=4° and 30°+ arccos(0.9)=56° by 10% Reduced layer thicknesses of the top layer (60) or all layers of the anti-reflective coating (6) differ from the color at an angle of incidence of 30° with undiminished layer thicknesses of the top layer (60) or all layers of the anti-reflective coating (5) in the CIE xyz color system differs by no more than Δx=0.05, Δy=0.05, or - the color of the residual reflection at an angle of incidence on the surface in the corresponding surface area (30, 32) lying between 45°-arccos(0.9)=19° and 45°+ arccos(0.9)=71° by 10% Reduced layer thicknesses of the top layer (60) or all layers of the anti-reflective coating (6) from the color at an angle of incidence of 45° with undiminished layer thicknesses of the anti-reflective coating (5) in the CIE xyz color system by no more than Δx=0.05, Δy=0.05 differs. 13. Transparent element (1) according to any one of claims 5 to 12, characterized in that the layers (51-56) are selected for given refractive indices with regard to their thickness so that with a reduction in the layer thickness of all layers by 10%, the photopic Reflectivity at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32) by no more than ΔR_ph=1%, particularly preferably by no more than ΔR_ph=0.5%, very particularly preferably by no more than ΔR_ph=0.25% of the value deviates with undiminished layer thicknesses. 14. Transparent element (1) according to one of claims 5 to 13, characterized by at least one of the following features: - The color of the residual reflection on the anti-reflective coating (5) at an angle of incidence of 0° on the surface in the corresponding surface areas (30, 32) with undiminished layer thicknesses of the anti-reflective coating (5) differs from the color at an angle of incidence of 0° in the CIE xyz color system by no more than Δx=0.05, Δy=0.05 with a reduction in the layer thickness of all layers of the antireflective coating (6) by 20%, preferably 30%, particularly preferably 40%, - The photopic reflectivity at an angle of incidence of 0° on the surface in the corresponding surface region (30, 32) with layer thicknesses of all layers reduced by 20%, preferably by 30%, particularly preferably by 40% differs from the photopic reflectivity at an angle of incidence of 0° undiminished layer thicknesses by no more than ΔR_ph=1.5%, - the color of the residual reflection on the anti-reflective coating (5) at an angle of incidence of 30° differs from the color at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32) in the CIE xyz color system by no more than Δx=0.02 , Δy=0.02, - the color of the residual reflection at 45° angle of incidence differs from the color at 0° angle of incidence on the surface in the corresponding surface area (30, 32) by no more than Δx=0.05, Δy=0.05, - the photopic reflectivity at 0° angle of incidence on the surface in the corresponding surface area (30, 32) is less than 1.5%, - the maximum reflectivity in the wavelength range between 450 nm and 700 nm is less than 1.5% at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32), - the absolute value of the difference between the photopic reflectivity at an angle of incidence of 30° and the photopic reflectivity at an angle of incidence of 0° on the surface in the corresponding surface region (30, 32) is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%, - the absolute value of the difference between the photopic reflectivity at an angle of incidence of 45° and the photopic reflectivity at an angle of incidence of 0° on the surface in the corresponding surface region (30, 32) 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 on the surface in the corresponding surface area (30, 32) is less than 1.5%, - The absolute amount of the difference of the average reflectivities at 30° angle of incidence and at 0° angle of incidence on the surface in the corresponding surface area (30, 32), averaged in the wavelength range between 450 nm and 700 nm, is absolutely less than 0.5%, preferred less than 0.3% more preferably less than 0.1%, - The absolute value of the difference between the average reflectivities at an angle of incidence of 45° and at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32), 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 in the maxima of the reflectivities in the wavelength range from 450 nm to 700 nm at an angle of incidence of 30° and at an angle of incidence of 0° on the surface in the corresponding surface region (30, 32) is less than 0.5%, preferably less than 0, 3% more preferably less than 0.1%. 15. Transparent element (1) according to claim 14, characterized by at least one of the features: - the photopic reflectivity at 0° angle of incidence on the surface in the corresponding surface area (30, 32) is less than 1%, preferably less than 0.8%, - The absolute value of the difference in the average reflectivity in the wavelength range between 450 nm and 700 nm at an angle of incidence of 30° to the average reflectivity in the wavelength range between 450 nm and 700 nm at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32) is less than 0.1%, - the absolute value of the difference between the average reflectivities at an angle of incidence of 45° and at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32), averaged in 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 on the surface in the corresponding surface area (30, 32) is less than 1.0%. 16. Transparent element (1) according to any one of claims 5 to 15, wherein the layers (51-56) are selected for given refractive indices with regard to their thickness so that with a reduction in the layer thickness of the top layer (60) by 10% or by 10 nm, depending on which of these two cases results in the smaller remaining layer thickness, and with the same layer thickness of the remaining layers (50 - 55), at least one of the following characteristics applies: - The color of the residual reflection at 0° angle of incidence on the surface in the corresponding surface area (30, 32) with reduced layer thickness of the top layer (60) differs from the color at 0° light incidence angle with undiminished layer thickness of the top layer (56) in the CIE xyz color system by no more than Δx=0.05, Δy=0.05, preferably no more than Δx=0.03, Δy=0.03, particularly preferably no more than Δx=0.02, Δy=0.02, - The photopic reflectivity at an angle of incidence of 0° on the surface in the corresponding surface area (30, 32) with a reduced layer thickness of the top layer (60) does not differ from the photopic reflectivity at an angle of incidence of 0° with an undiminished layer thickness of the top layer (56). more than ΔR_ph=1.5%. 17. Transparent element (1) according to any one of claims 5 to 16, characterized in that the substrate (3) is a sapphire substrate. 18. Transparent element (1) according to any one of claims 5 to 17, 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. 19. Transparent element (1) according to one of claims 5 to 18, characterized by layers (51, 53) with a high refractive index made of at least one of the materials silicon nitride, Si3N4, aluminum nitride, AlN, aluminum oxide, Al2O3 or aluminum silicon oxynitride , AlwSixNyOzist. 20. Transparent element (1) according to one of claims 5 to 19, characterized in that the antireflection coating (5) has at most twenty, preferably at most fifteen layers. 21. Transparent element (1) according to one of claims 5 to 20, characterized by at least one of the following features: - The ratio of the layer thickness of the top layer (56) of the anti-reflective coating (5) to the layer thickness of the third top 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 top pair of layers to the product of the layer thicknesses of the second top 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 among the layers with a lower refractive index to the layer thickness of the thickest layer among the layers with a higher refractive index is between 0.2 and 3, with a range from 1.5/F(n) to 2.5/ F(n) is excluded, where F(n) is given by F(n)=(n-1)/(0.47) and n denotes the refractive index of the substrate, - the ratio of the standard deviation of the layer thicknesses of the layers to the layer thickness of the thickest layer of the anti-reflective coating is in a range from 0.25 to 0.45. 22. Transparent element (1) according to any one of claims 5 to 21, designed as a watch glass or magnifying glass of a watch glass.