Antireflective coating with stable reflectivity and color under angle and under abrasion.

专利摘要:
The aim of the invention is to provide a mechanically stable anti-reflection system. For this purpose, a method for producing a transparent element (1) is provided as well as the transparent element (1), comprising a transparent substrate (3) and on this substrate (3) a multi-layer anti-reflective coating (5), which comprises at least four layers, wherein layers (51, 53) with a high refractive index alternate with layers (50, 52, 54) with a lower refractive index, and wherein the layers (51, 53) with a higher refractive index have a greater hardness than the layers (50, 52, 54) with a lower refractive index, and wherein the top layer (60) of the multilayer anti-reflective coating (5) is a layer with a lower refractive index, and wherein the layers (5154) are selected for given refractive indices with regard to their thickness so that when the Layer thickness of the top layer (60) by 10% or 10 nanometers, depending on which of these two cases results in the lower remaining layer thickness, at least one of the following features applies: the color of the Res The reflection of the anti-reflective coating (5) at an angle of incidence of 0 ° with reduced layer thickness differs from the color at an angle of incidence of light at 0 ° with an undiminished layer thickness of the top layer (60) in the CIE xyz color system by no more than Δx = 0.05, Ay = 0.05, preferably not more than Δx = 0.03, Δy = 0.03, particularly preferably not more than Δx = 0.02, Δy = 0.02, the photopic reflectivity of the antireflective coating (5) at an angle of incidence of 0 ° with a reduced layer thickness differs from the photopic reflectivity below 0 ° Angle of incidence with undiminished layer thickness by no more than ΔR_ph = 1.5%.
公开号:CH714953B1
申请号:CH01105/19
申请日:2018-03-05
公开日:2021-11-30
发明作者:Apitz Dirk；Henn Christian；Brauneck Ulf；Bourquin Sébastian
申请人:Schott Ag；
IPC主号:

专利说明:

[0001] Antireflective coating systems are state of the art today and are used in a variety of ways. Areas of application include image glazing, optical components such as lenses for cameras, for example. These applications are not exposed to any strong mechanical stress.
EP 2 492 251 B1 describes the production of anti-reflective layer systems for, inter alia, the watch glass industry. In addition to the anti-reflective 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 layer systems does not make sense, as these can be completely removed due to the mechanical stress and the reflection of the substrate material arises. The hard AR system based on the development according to EP 2 492 251 B1 provides an anti-reflective system which is mechanically significantly more stable than conventional optical coatings.
Since sapphire is often used as watch glass in the watch industry, but antireflective coatings are generally much softer than sapphire, it would be desirable to be able to maintain the antireflective effect as well as possible despite mechanical stress, ie that the residual reflection also after mechanical stress remains as low as possible. According to EP 2 492 251 B1, this is achieved by the hard material layers, which bring about a high level of abrasion resistance in the layer system and thus only a slight change in the layer thickness.
[0004] Two-material systems traditionally play the main role among the hard material layers. Above all, the oxides and nitrides of Cr, Si, Ti and Zr should be mentioned here. These are primarily used in the coating of tools, so they do not have to be transparent for this application. Well-known transparent hard material layers are e.g. Al2O3, as described in DE 20106167, and yttrium-stabilized ZrO2. EP 1 453 770 B1 describes glass ceramic substrates which are coated with carbon-doped silicon nitride.
In WO 2009/010180 A1 and DE 10 2008 054 139 A1, aluminum-doped SiN or SiON layers with a scratch protection effect are described 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 contains nano-crystallites. The disadvantage of known antireflective coatings is that, inter alia, the color of the residual reflection under inclined light incidence angle, the color of the residual reflection after abrasion and the color of the residual reflection after abrasion at an angle, and the reflectivity after abrasion at an angle are not taken into account. It would generally be desirable if a change in reflectivity after abrasion can be reduced.
The aim of the invention is therefore to provide a mechanically stable anti-reflective system, which has a mechanical resistance comparable to the prior art to anti-reflective systems with hard material layers and about optical properties (average reflectivity, photopic reflectivity, color of the Residual reflection) both before and after abrasion, optimized both at the normal angle of incidence and at various other angles. B. unpleasant color effects on bevels (at angles) and changes in color effects and reflectivity due to abrasion are reduced.
The abrasion can with an abrasion test, for. B. the modified Bayer test, based on ASTM F735-11, but preferably with 2 kg of corundum sand and 8000 cycles. This modified Bayer test is also described in the above-mentioned documents DE 10 2016 125 689 A1 and DE 10 2014 104 798 A1, the disclosure of which in this regard is also made the subject 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 the typical layer thicknesses, this amount of material corresponds to more than ten percent of the layer thickness. Tests have shown that the modified Bayer test, applied to the coatings described in EP 1 453 770 B1, DE 10 2014 104 798 A1 and DE 10 2016 125 689 A1, causes such a material removal from the top layer. For example, the Bayer test can reduce the average layer thickness from 100 nm to 80 nm. 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 resultant reflectivity or a macroscopic resultant residual reflection color, which is similar to the visual Impression corresponds.
In order to make the change in the residual reflection as insensitive as possible to abrasion, the invention is based on the idea of comparing or selecting layer sequences with one another in the design of the layer system to the effect that the smallest possible change in optical parameters with regard to the color of the residual reflection, its angle dependency and, above all, the The intensity of the residual reflection is present when the layer thickness of the top layer of the layer system is changed.
For this purpose, a transparent element is provided according to the invention, comprising a transparent substrate and on this substrate a multilayer anti-reflective coating which comprises at least four layers, layers with a high refractive index alternating with layers with a lower refractive index, and wherein the layers with a higher refractive index typically have a greater hardness than the layers with a lower refractive index, and wherein the top layer of the multilayer anti-reflective coating is a layer with a lower refractive index, and wherein the layers are selected with regard to their thickness for given refractive indices so that a reduction the layer thickness of the top layer by 10% or 10 nm, depending on which of these cases results in the lower remaining layer thickness, so that the layer thickness after the reduction in the first case is 0.9 times the original layer thickness, at least one of the following Features applies:the color of the residual reflection at 0 ° angle of incidence with reduced layer thickness differs from the color at 0 ° angle of incidence of light with unchanged layer thickness of the top layer (54) in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.05,the photopic reflectivity at a 0 ° angle of incidence with a reduced layer thickness differs from the photopic reflectivity at a 0 ° angle of incidence with an undiminished layer thickness by no more than ΔR_ph = 1.5%.
The difference is to be understood in terms of amount.
The terms “higher refractive index” and “lower refractive index” are to be understood as a comparison relative to 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 (daytime vision). For the information given here, the light source according to ISO standard 3664 was based on the standard illuminant D65, a radiation distribution with a color temperature of 6504 Kelvin.
The case of a reduction in the layer thickness by 10 nanometers results in the case of layer thicknesses of the top layer of less than 100 nanometers.
According to a further development of the invention, the anti-reflective coating can also be designed so that the color of the residual reflection at 0 ° angle of incidence with reduced layer thickness differs from the color at 0 ° light angle of incidence with undiminished layer thickness of the top layer in the CIE xyz color system not more than Δx = 0.03, Δy = 0.03, preferably not more than Δx = 0.02, Δy = 0.02.
Furthermore, the two above-mentioned features Δx = 0.05, Δy = 0.05 and / or a change in the photopic reflectivity by a maximum of ΔR_ph = 1.5% according to a development of the invention even with a significantly greater reduction in the layer thickness of the top layer, namely 20% , or 30%, or even 40% can be achieved.
Preferably, the layers of the anti-reflective coating are selected for given refractive indices with regard to their thickness so that the color of the residual reflection at a 30 ° angle of incidence with a layer thickness reduced by 10% from the color at a 30 ° angle of incidence with an undiminished layer thickness in the CIE xyz- Color system differs by no more than Δx = 0.05, Δy = 0.05.
According to a further development, the layer system is also designed so that after the reduction of the layer thickness of the top layer to 0.9 times the photopic reflectivity at 0 ° angle of incidence with undiminished layer thickness by no more than ΔR_ph = 1%, particularly preferred by no more than ΔR_ph = 0.5%, very particularly preferably by no more than ΔR_ph = 0.25%.
According to yet another development of the invention, the layers are selected for given refractive indices in terms of their thickness so that the color of the residual reflection at 45 ° angle of incidence with 10% reduced layer thickness from the color at 45 ° angle of incidence with undiminished layer thickness in CIE xyz Color system differs by not more than Δx = 0.05, Δy = 0.05, preferably Δx = 0.03, Δy = 0.03, particularly preferably Δx = 0.02, Δy = 0.02.
The layer system can also be further coordinated so that the transparent element has at least one of the following features, preferably also several, in particular all features:the color of the residual reflection on the anti-reflective coating (5) at a 30 ° angle of incidence differs from the color at a 0 ° angle of incidence in the CIE xyz color system by no more than Δx = 0.02, Δy = 0.02,the color of the residual reflection at a 45 ° angle of incidence does not differ from the color at a 0 ° angle of incidence by no more than Δx = 0.05, Δy = 0.05,the photopic reflectivity at an angle of incidence of 0 ° 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 °,the absolute value of the difference between the photopic reflectivity at a 30 ° angle of incidence and the photopic reflectivity at a 0 ° angle of incidence 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 ° 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 an angle of incidence of 0 °, is less than 1.5%,the absolute value of the difference between the average reflectivities at a 30 ° angle of incidence and at a 0 ° angle of incidence, 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 value of the difference between the average reflectivities at an angle of incidence of 45 ° and an angle of incidence at 0 °, averaged in the wavelength range between 450 nm and 700 nm, is less than 0.5%the absolute amount of the difference between the maxima of the reflectivities in the wavelength range between 450 nm and 700 nm at a 30 ° angle of incidence and at a 0 ° angle of incidence is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%,the absolute amount of the difference between the maxima of the reflectivities in the wavelength range between 450 nm and 700 nm at 45 ° angle of incidence and under 0 ° angle of incidence is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1% here denotes the average value of the reflectivity in the wavelength range from 450 to 700 nm.
In a further development of this embodiment, the coating can even meet at least one of the following features:the photopic reflectivity at an angle of incidence of 0 ° is less than 1%, preferably less than 0.8%,the absolute value of the difference between the photopic reflectivity at a 30 ° angle of incidence and the photopic reflectivity at a 0 ° angle of incidence is less than 0.1%,the absolute value of the difference between the average reflectivity in the wavelength range between 450 nm and 700 nm at a 30 ° angle of incidence to the average reflectivity in the wavelength range between 450 nm and 700 nm at a 0 ° angle of incidence is less than 0.1%,the absolute value of the difference between the photopic reflectivity at a 45 ° angle of incidence and the photopic reflectivity at a 0 ° angle of incidence is less than 0.2%,the absolute amount of the difference between the average reflectivity in the wavelength range between 450 nm and 700 nm at a 45 ° angle of incidence to the average reflectivity in the wavelength range between 450 nm and 700 nm at a 0 ° angle of incidence is absolutely less than 0.2%,the average reflectivity, averaged in the range between 450 nm and 700 nm at an angle of incidence of 0 °, is less than 1.0%.
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 terms of their importance or prioritization. Such targets can be given with values e.g. B. can be defined as links such as “less than” or “as close as possible to”. Colors are defined as “as close as possible to” the desired color location, reflectivities as “less than” a desired limit. Furthermore, deviations can then be penalized and, with these penalties, the layer thicknesses of the design can be optimized in such a way that a penalization that is as minimal as possible is achieved. With weightings, deviations in various parameters can be included in the penalization to different degrees. So z. B. the residual reflection color or the reflectivity under 45 ° be weighted less important than under 0 °. The weightings are adjusted during the process in such a way that the desired results for the coating characteristics are achieved.
In particular, at least two, preferably several designs are defined which are identical in all layer thicknesses and layer materials and differ only in the layer thickness of the last layer. Is there e.g. B. a coating of 5 layers with two alternating materials, where d1, d2, ... are the layer thicknesses and the L and H are the two materials (with low and high refractive index) a coating design (B1) could now be described as follows : B1: d1 [L] d2 [H] d3 [L] d4 [H] d5 [L].
[0024] Here, [L] denotes a layer with a low refractive index, [H] a layer with a high refractive index, d1-d5 are the respective layer thicknesses of these layers.
Other designs with changed thickness of the last layer could now be z. B. describe as follows B2: d1 [L] d2 [H] d3 [L] d4 [H] (d5-20nm) [L] or B3: d1 [L] d2 [H] d3 [L] d4 [H] ( d5-40nm) [L].
In particular, a condition d5 * 0.9 [L] with unchanged layer thicknesses d1 to d4 according to the most general embodiment of the invention, in which the layer thickness of the top layer differs by 10%, can be introduced.
The method now includes that one defines the targets described above for each of these designs and adjusts all designs simultaneously (simultaneously) by changing the layer thicknesses d1, d2, ... the designs are still just the same Differentiate between layer thickness differences. The targets for the different coating designs can differ and be weighted differently. So z. B. the residual reflection color or the reflectivity for the design in which the last layer is reduced in thickness by 40 nm, be weighted less important than for the design in which the last layer is not reduced in thickness.
[0028] An automatic adjustment method which is subjected to this procedure generally generates several different solutions that are differently optimal or differently optimal with regard to different parameters. So z. B. one solution keep the residual reflection color by reducing the thickness of the last layer more constant 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, which comprise at least four layers, layers with a high refractive index (51, 53) alternating with layers (50, 52, 54) with a lower refractive index, the layers (51, 53) with a higher refractive index have a greater hardness than the layers (50, 52, 54) with a lower refractive index, and wherein the top layer (54) of the multi-layer anti-reflective coating (5) is a layer with a lower refractive index, taking into account the refractive index of the substrate at least one of the parametersColor of the residual reflection at a light incidence angle of 0 ° andPhotopic reflectivity calculated at an angle of incidence of 0 °, whereby the two antireflective coatings only differ in terms of the layer thickness of the top layer, so that the layer thickness of one antireflective coating is reduced by at least a factor of 0.9 compared to the layer thickness of the other antireflective 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 a 0 ° angle of incidence with a reduced layer thickness differs from the color at a 0 ° angle of incidence of light with an undiminished layer thickness of the top layer in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.05,the photopic reflectivity at 0 ° angle of incidence with reduced layer thickness differs from the photopic reflectivity at 0 ° angle of incidence with unchanged layer thickness 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 additional pair and at least one of the conditions is checked if the condition is not met for the first pair, and wherein a layer sequence with a thicker uppermost layer is selected from a pair of anti-reflective coatings which meets at least one of the conditions, and wherein an anti-reflective coating is deposited with this selected layer sequence on a substrate.
Instead of just one pair, a larger number of designs can be brought into the simultaneous fitting process, e.g. B. four designs with the second in the last layer thickness, as just described, reduced by 10%, a third with 20% layer thickness reduction and a fourth with 30% layer thickness reduction.
If one of the conditions is not met, according to the invention, the search is in any case continued among the solutions found. Furthermore, it is typically necessary to optimize the weightings and values of the targets so that the adaptation of the designs generates solutions that meet the desired conditions or meet them as well as possible. This search under can also be continued when a suitable pair of anti-reflective coatings has already been found, either to meet further conditions that are already mentioned above, or to find a layer system that is as optimal as possible. In general, a check with regard to the above-mentioned conditions can be carried out for a large number of pairs (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 can be selected in which the smallest difference in the color of the residual reflection is present at 0 ° light incidence angle and / or the smallest difference in photopic reflectivity at 0 ° light incidence angle and then this layer system is deposited.
The selection of an anti-reflective layer system from a specific pair of anti-reflective coatings can be made depending on whether further conditions exist, 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 so thatthe color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at a 30 ° angle of incidence does not differ by more than Δx = 0.05, Δy = 0.05, orthe 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.
In particular, the invention is 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 providing a high quality, hard and abrasion-resistant anti-reflective layer system, come into their own.
Silicon nitride (Si3N4), aluminum nitride (AlN), aluminum oxide (Al2O3), as well as 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 are particularly suitable layer materials. The materials can be doped or do not have to be in pure form. Aluminum nitride with a proportion of silicon (e.g. between 0.05 and 0.25) or, conversely, silicon with a proportion of aluminum (again e.g. between 0.05 and 0.25) can be used as the material for the higher refractive index layers.
According to a further development of the invention, all of the above-mentioned features with regard to reflectivity and color location can also be fulfilled if the layer thickness of the top layer is reduced even further, to at most 0.8 times, particularly preferably at most 0.7 times. times, particularly preferably at most 0.6 times, the undiminished layer thickness.
Brief description of the figures:
1 shows two transparent elements with four-layer anti-reflective coatings. Fig. 2 shows two transparent elements with anti-reflective coatings with five-layer anti-reflective coatings. 3 shows diagrams of the color locus for various antireflective coatings with residual blue reflection. FIG. 4 shows diagrams of the color point for various antireflective coatings with neutral or colorless residual reflection, and FIG. 5 shows a frequency distribution of the layer thickness of the lowest pair of layers for a number of antireflective coatings on a sapphire substrate. A corresponding frequency distribution for coatings on a borosilicate glass substrate is shown in FIG. 6. 7 shows a frequency distribution of the distance of the third uppermost interface from the surface for a number of anti-reflective coatings on a sapphire substrate. 8 shows a corresponding frequency distribution for coatings on a borosilicate glass substrate. 9 shows a frequency distribution of the difference in the layer thicknesses of the top pair of layers and the second top pair of layers for a number of anti-reflective coatings on a sapphire substrate. A corresponding frequency distribution for coatings on a borosilicate glass substrate is shown in FIG. 10. FIGS. 11 to 14 show diagrams in which the layer thicknesses of the uppermost layers are plotted for different types of anti-reflective coatings according to the invention. FIGS. 15 to 18 show diagrams in which the layer thicknesses of the lowermost high-index layers are plotted for various types of antireflective coatings according to the invention.
Fig. 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 anti-reflective coating 5 is deposited on the substrate 3. This has at least four layers 51, 52, 53, 54. The layers 51, 53 have high refractive index and the layers 52, 54 have low refractive index, so that the layers 51, 53 have a higher refractive index than the layers 52, 54. The layer materials are marked by different hatching. As can be seen from the illustration, layers with a higher refractive index 51, 53 alternate with layers 52, 54 with a lower refractive index. A great hardness and resistance of the anti-reflective coating 5 is brought about in particular by the layers 51, 53 with a higher refractive index, which have a greater hardness than the low refractive index layers.
The layer 54 forms the top layer 60 of the anti-reflective coating and is a low refractive index layer. As a result, this layer 60 can be more easily removed by abrasion.
The transparent element 1 shown in partial image (b) differs from element 1 according to partial image (a) only in that in the case of the anti-reflective coating 6, the layer thickness of the top layer 60 is reduced by an amount. Such a situation can arise if the anti-reflective coating 5 according to the invention is worn away by abrasion in the course of time, as shown in part (a). 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, with a decrease in layer thickness according to the change between the two partial images (a), (b) the color of the residual reflection and / or the The reflectivity of the surface remains almost unchanged. In particular, the color of the residual reflection at an angle of incidence of 0 ° with reduced layer thickness according to part (b) can differ from the color with unchanged layer thickness of the top layer 60, 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 at an angle of incidence of 0 ° with a reduced layer thickness can differ from the photopic reflectivity at an angle of incidence of 0 ° with an undiminished layer thickness by no more than ΔR_ph = 1.5%. With an anti-reflective coating 5, these criteria can also be met if the decrease in the layer thickness d is at least 0.1 * d, that is to say at least 10%.
In general, the anti-reflective coating 5 can be designed so that it has all or most (many, preferably most, particularly preferably almost all, very particularly preferably all) the following properties at the same time, with the layer thickness of the top layer 60 remaining the same: a ) The anti-reflective 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. E.g. 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 a 30 ° angle of incidence differs from the color at a 0 ° angle of incidence by no more than z. B. 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. B. 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% (for example also less than 2%, preferably less than 1.5%, especially preferably less than 1.0%, very particularly preferably less than 0.8%). e) The photopic reflectivity of the anti-reflective coating 5 at a 30 ° angle of incidence differs from the value at a 0 ° angle of incidence by less than 0.2%, particularly preferably by less than 0.1%. f) The photopic reflectivity of the anti-reflective 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 range between 450 nm and 700 nm, for example) at an angle of incidence of 0 ° is less than 1.5%, preferably less than 1.25%, particularly preferably less than 1 , 0%. h) The average reflectivity of the anti-reflective coating 5 at a 30 ° angle of incidence differs from the value at a 0 ° angle of incidence by less than 0.5%, preferably by less than 0.2%, particularly preferably by less than 0.1%. i) The average reflectivity of the anti-reflective 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 range between, for example, 450 nm and 700 nm) is less than 2%, preferably less than 1.5%, particularly preferably less than 1.0%, at an angle of incidence of 0 °. k) the absolute reflectivity at a 30 ° angle of incidence differs from the value at a 0 ° angle of incidence 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%, very particularly preferably by 40%, or even by 50%, so that an anti-reflective coating 6 is obtained, such as it shows an example of partial image (b) of FIG. 1, the following features can be present individually or in combination: Coating 5 with undiminished layer thickness of the layer 60 at an angle of incidence of 0 ° by not more than Δx = 0.05, Δy = 0.05, preferably not more than Δx = 0.03, Δy = 0.03, particularly preferably not more as Δx = 0.02, Δy = 0.02, very particularly preferably by not more than Δx = 0.01, Δy = 0.01. n) The color of the residual reflection at a 30 ° angle of incidence of the anti-reflective coating 6 with a reduced layer thickness of the layer 60 differs from the color of the anti-reflective coating 5 with an undiminished layer thickness of the layer 60 at a 30 ° angle of incidence by no more than Δx = 0.05, Δy = 0.05, preferably not more than Δx = 0.03, Δy = 0.03, particularly preferably not more than Δx = 0.02, Δy = 0.02, very particularly preferably not more than Δx = 0.01 , Δy = 0.01. o) The color of the residual reflection of the anti-reflective coating 6 with a reduced layer thickness of the layer 60 at a 45 ° angle of incidence differs from the color of the anti-reflective coating 5 with an undiminished layer thickness of the layer 60 at a 45 ° angle of incidence by no more than Δx = 0.05 , Δy = 0.05, preferably not more than Δx = 0.03, Δy = 0.03, particularly preferably not more than Δx = 0.02, Δy = 0.02, very particularly preferably not more than Δx = 0.01, Δy = 0.01. p) The photopic reflectivity of the anti-reflective coating 6 with a reduced layer thickness of the layer 60 at a 0 ° angle of incidence differs from the color of the anti-reflective coating 5 with an undiminished layer thickness of the layer 60 at a 0 ° angle of incidence by no more than ΔR_ph = 1.5% , preferably 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%.
In the example shown in Fig. 1, the anti-reflective coating 5 consists of a total of four layers, the lowermost 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 higher refractive index layers. In the case of a substrate with a refractive index greater than 1.65, however, it is advantageous to provide a lower refractive index layer in contact with the substrate. Such an example is shown in Fig. 2, also with a partial image (a) with undiminished layer thickness of the top layer 60 and a partial image (b) with a similar anti-reflective coating 6, but in which the top layer 60 is at most 0 in its thickness .9 times the layer thickness d of the top layer 60 shown in partial image (a) is reduced.
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 above 1.65 and the anti-reflective coating 5 being a sequence of has at least five alternating layers with a lower and a higher refractive index, the lowermost layer 50 being a layer with a lower refractive index.
The substrate 3 of this embodiment is preferably a sapphire. The transparent element can then, for example, be a watch glass or a magnifying glass for a watch glass, such as is used to enlarge the date display. In addition to sapphire, soda-lime glass, borofloat glass, aluminosilicate glass, lithium aluminosilicate glass, glass ceramics and optical glass, for example glass with the trade names NBK7, D263 or B270, can also be used as substrate material.
In the case of a five-layer anti-reflective coating on a high-index substrate, as shown as an example in FIG. 5, the coating 5 can generally be characterized as follows according to two embodiments of the invention with regard to the layer thicknesses of the individual layers: Case a) The Layer thicknesses are: thickness d1 of the first layer on the substrate 3, i.e. the bottom layer 50: 5 nm - 60 nm, thickness d2 of the second layer 51: 5 nm - 50 nm, thickness d3 of the third layer 52: 10 nm - 200 nm , Thickness d4 of the fourth layer 53: 100 nm - 200 nm, thickness d5 of the fifth and topmost layer 54: 70 nm - 120 nm, case b) The layer thicknesses are: Thickness d1 of the first layer on the substrate 3: 5 nm - 60 nm, thickness d2 of the second layer 51: 30 nm - 200 nm, thickness d3 of the third layer 52: 10 nm - 200 nm, thickness d4 of the fourth layer 53: 150 nm - 300 nm, thickness d5 of the fifth and topmost layer 54: 70 nm - 120 nm.
The first case typically results in an antireflective coating with blue or color-neutral residual reflection, the second case generally results in a purple residual reflection. The two designs differ from one another with regard to the layer thickness ranges of the second and fourth layers.
In both cases, the following relationship can apply to the layer thicknesses d1, d2, d3, d4, d5: D = 85 nm + 1.7 * d1 + 1.1 * d2 - 0.9 * d3 + 0.0138 * (d3-60 nm) <2>. D indicates the value of the layer thickness d4 of the fourth layer with a deviation of a maximum of ± 15%, preferably a maximum of ± 10%, particularly preferably a maximum of ± 5%. Antireflection coatings with these features have proven to be particularly favorable with regard to the stability of the color locus of the residual reflection and the reflectivity with abrasion of the top layer 54, 60.
As an exemplary embodiment of the invention, FIG. 3 shows four diagrams of the color locations of the residual reflection on different anti-reflective coatings. As in the example in FIG. 2, the coatings are designed as five-layer anti-reflective coatings 5. A sapphire disk is used as the substrate 3. In the diagrams of the partial images (a) to (d), three points are drawn in, which characterize the color of the residual reflection at 0 °, 20 ° and 40 ° angles of incidence of light. The values of all diagrams are calculated.
Partial image (a) shows the x and y values of the color of the residual reflection with undiminished layer thickness of the top layer 60. In partial image (b) the layer thickness of the top layer 60 is reduced by 10% and the layer thickness of the top layer is reduced that is, 0.9 times the layer in the example from part (a). In partial image (c) the layer thickness of the top layer 60 is reduced by 20% and in partial image (c) by 30%.
A comparison of the color locations between the partial images (a), (b) shows that the color of the residual reflection at 0 ° angle of incidence with reduced layer thickness differs from the color at 0 ° angle of light incidence with undiminished layer thickness of the top layer 54, 60 in the CIE xyz color system does not differ by more than Δx = 0.05, Δy = 0.05. This also applies to all points, including angles of incidence of 20 ° and 40 °. Only when the layer thickness is reduced by 30% according to partial image (d) is a single point found, which has an x value of greater than 0.25 and thus has a deviation of slightly more than 0.05.
The photopic reflectivities (data in percent) in the layer system according to partial image (a) are 1.37 at 0 °, 0.935 at 20 ° and 1.148 at 40 °. In partial image (b), the photopic reflectivities are 0.996 at 0 °, 0.985 at 20 ° and 1.15 at 40 °. The changes in the photopic reflectivities are: ΔR_ph (0 °) = 1.37-0.996 = 0.374%; ΔR_ph (20 °) = 0.935-0.985 = -0.05%; ΔR_ph (40 °) = 1.148 - 1.15 = -0.002%.
Consequently, all differences, as provided according to the invention, are clearly less than 1.5% in terms of amount, in particular even less than 0.5%.
The changes with regard to the photopic reflectivity and color of the residual reflection are therefore only very small if an antireflective coating according to partial image (a) experiences a thinning of the top layer 60 due to abrasion.
The layer thicknesses of the anti-reflective coating according to partial image (a), that is to say before a reduction of the top layer by abrasion, are similar to a further exemplary embodiment. According to this exemplary embodiment, the layer thicknesses are in detail: bottom layer 50 (lower refractive index): 55 nm, subsequent layer 51 (higher refractive index): 17 nm, subsequent layer 52 (lower refractive index): 80 nm, subsequent layer 53 (higher refractive index): 125 nm, top layer 54 or 60 (lower refractive index): 80 nm.
The following table lists the calculated values for the CIE color location (x, y) at different angles of incidence of light before and after a reduction in the layer thickness of the top layer 54, 60 by 10 nm for the above-mentioned layer system: 0 0 0.162 0.145 15 0 0.162 0.135 0.000 0.010 30 0 0.171 0.122 0.009 0.023 45 0 0.211 0.164 0.049 0.019 0 10 0.171 0.099 0.009 0.046 15 10 0.176 0.097 0.014 0.038 30 10 0.197 0.109 0.026 0.013 45 10 0.249 0.171 0.038 0.007
The changes in the color values .DELTA.x and .DELTA.y for the angles 15 °, 30 ° and 45 ° with a reduction by 0 nm, that is, with an undiminished layer thickness, relate to the color values at 0 ° light incidence angle. As an example, the change in the color value Δx of 0.009 at a light incidence angle of 30 ° is the difference to the value x at 0 ° and the layer thickness is also unchanged. The changes Δx, Δy with reduced layer thickness and angles of incidence of light of 15 °, 30 °, 45 ° (last three lines of the table) relate to the color values at the same angle but unchanged layer thickness. The change .DELTA.x of 0.038 in the last line of the table is accordingly the absolute amount of the difference between the color values x under 45 ° light incidence with an undiminished layer thickness and a layer thickness reduced by 10 nm.
4 shows a further example according to the invention on the basis of diagrams of the calculated color values of the residual reflection. The color of the residual reflection was determined for reflection at angles of incidence of light of 0 °, 20 °, 40 ° and 60 °. Partial image (a) again shows the color values with unchanged layer thickness and the partial images the color values with the layer thickness of the top layer 60 reduced by 20% and 50%. Here, none of the partial images (b) and (c) deviates from the color value according to partial image (a) by more than 0.05, which is remarkable in view of the significant reduction in the top layer 60 to half the layer thickness.
The following values were determined for the photopic reflectivity: In partial image (a), undiminished layer thickness, the reflectivity at angles of incidence of light of 0 °, 20 ° and 40 ° is 1.658, 1.536 and 1.590. In partial image (b), the layer thickness of the top layer reduced by 20%, the reflectivity at light incidence angles of 0 °, 20 ° and 40 ° is 1.063, 1.076 and 1.480. In partial image (c), the layer thickness of the top layer halved, the reflectivity at angles of incidence of light of 0 °, 20 ° and 40 ° is 3.321, 3.403 and 4.100.
Although the reflectivity increases with strong abrasion, the color changes only remain very small.
In a further exemplary embodiment with layer thicknesses similar to those of the anti-reflective coating according to FIG. 4, partial image (a), the individual layers are given by: lowest layer 50 (lower refractive index): 35 nm, subsequent layer 51 (higher refractive index) : 25 nm, next layer 52 (lower refractive index): 40 nm, next layer 53 (higher refractive index): 135 nm, top layer 54 or 60 (lower refractive index): 100 nm.
The following table lists the calculated values for the CIE color location (x, y) of this exemplary embodiment at different angles of incidence of light before and after a reduction in the layer thickness of the top layer 54, 60 by 10 nm: 0 0 0.298 0.298 15 0 0.299 0.299 0.001 0.001 30 0 0.297 0.315 0.001 0.017 45 0 0.299 0.347 0.001 0.049 0 10 0.324 0.347 0.026 0.049 15 10 0.322 0.348 0.023 0.049 30 10 0.315 0.374 0.018 0.059 45 10 0.309 0.379 0.010 0.032
The changes in the color values .DELTA.x and .DELTA.y for the angles 15 °, 30 ° and 45 ° with a reduction by 0 nm, i.e. with the layer thickness remaining unchanged, relate, as in the previous table, to the color values at a light incidence angle of 0 °. As an example, the change in the color value Δy of 0.049 at a 45 ° angle of incidence of light is the difference to the value y at 0 ° and also with an undiminished layer thickness. The changes Δx, Δy with reduced layer thickness and angles of incidence of light of 15 °, 30 °, 45 ° (last three lines of the table) relate, as in the previous table, to the color values at the same angle but unchanged layer thickness.
In the table below, a further exemplary embodiment according to the invention is compared with a comparative example. The coatings were subjected to a modified Bayer test, as mentioned above, the reflectivity and the color location being measured before and after the abrasion test. Thickness of 1st layer 50 (low index) 32.9 nm 15.0 nm Thickness of 2nd layer 51 (high index) 25.4 nm 30.0 nm Thickness of 3rd layer 52 (low index) 41.3 nm 27.0 nm Thickness of 4th layer 53 (high Index) 152.9 nm 136.0 nm Thickness of 5th layer 54 (low index) 104.8 nm 92.0 nm Calculated thickness of 4th layer 136.5 nm 134.2 nm Deviation of 4th layer 12.1% 1.3% photopic reflectivity before abrasion below 0 ° 0.89% OK 1.02 % OK photopic reflectivity after abrasion test below 0 ° 2.60% not OK 1.89% OK Change in the CIE color locus below 0 ° 0.155 not OK 0.016 OK Change in photopic reflectivity below 0 ° 1.71% not OK 0.87% OK
As can be seen from the table, the comparative example is slightly better than the coating according to the invention with regard to the photopic reflectivity before the abrasion test. However, after abrasive action, the coating according to the invention changes the color of the residual reflection and the reflectivity considerably less than the comparative example.
Furthermore, the invention is not limited to four- or five-layer coatings, as shown by way of example in FIGS. 2 and 3. Even more layers can be provided. However, it is generally preferred that the anti-reflective coating 5 has a maximum of twelve, particularly preferably a maximum of ten layers, in order to keep the manufacturing effort within limits.
Further exemplary embodiments are explained below. The table below lists the optical properties before and after abrasion of the top layer and under inclined light for five examples. Examples 3 to 5 are optimized not only for optical properties that are as insensitive as possible to abrasion under perpendicular incidence of light, but additionally also under inclined incidence of light. Examples 1 and 2 each meet only one of the two criteria of a slight change in color and change in photopic reflectivity under abrasion, whereas Examples 3 to 6 meet both criteria, namely that, firstly, the color of the residual reflection at an angle of incidence of 0 ° with a reduced layer thickness differs from of the color at 0 ° light angle of incidence with undiminished layer thickness of the top layer 54 in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.05 and, secondly, the photopic reflectivity at 0 ° angle of incidence with reduced layer thickness differs from the photopic reflectivity at 0 ° angle of incidence does not differ by more than ΔR_ph = 1.5% with undiminished layer thickness. The examples were optimized for a color point of the residual reflection in the vicinity of x = 0.331, y = 0.331.
Tables: optical properties before and after abrasion
example 1
CIE color locus (x, y)
0 0 0.33 0.330 0.321 0.010 0 °, 100% layer (new) OK, R low 15 0 0.35 0.368 0.322 0.038 30 0 0.53 0.428 0.307 0.100 strong color deviations at viewing angle 45 0 1.47 0.419 0.315 0.089 60 0 5.45 0.377 0.332 0.046 0 10 0.83 0.403 0.327 0.072 strong color deviations after abrasion 15 10 0.91 0.411 0.348 0.082 30 10 1.32 0.423 0.318 0.093 45 10 2.68 0.416 0.334 0.085 60 10 7, 34 0.380 0.347 0.052 0 30 3.60 0.336 0.287 0.044 15 30 3.77 0.343 0.291 0.042 30 30 4.45 0.361 0.308 0.038 45 30 6.35 0.374 0.336 0.043 60 30 11.72 0.363 0.352 0.038
Example 2
0 0 0.33 0.334 0.321 0.010 0 °, 100% layer (new) OK 15 0 0.34 0.377 0.325 0.046 30 0 0.54 0.491 0.305 0.162 strong color deviations at viewing angle 45 0 1.92 0.517 0.333 0.186 60 0 7.61 0.458 0.365 0.131 0 10 0.91 0.412 0.419 0.120 strong color deviations after abrasion 15 10 0.97 0.436 0.405 0.128 30 10 1.40 0.446 0.383 0.126 45 10 3.45 0.494 0.374 0.169 60 10 10.27 0.504 0.374 0.178 0 30 3.77 0.329 0.321 0.010 15 30 3.91 0.345 0.325 0.015 30 30 4.76 0.390 0.342 0.060 strong color deviations at viewing angle after abrasion 45 30 7.83 0.423 0.366 0.098 60 30 15.72 0.399 0.376 0.082
Example 3
[0069] 0 0 0.80 0.331 0.331 0.000 0 °, 100% layer (new) OK 15 0 0.85 0.339 0.342 0.014 30 0 1.08 0.352 0.363 0.038 45 0 2.02 0.348 0.357 0.031 very slight color deviations under the viewing angle 60 0 5.85 0.330 0.337 0.006 0 10 1.52 0.360 0.372 0.050 very slight color deviations after abrasion 15 10 1.60 0.361 0.374 0.052 30 10 1.95 0.359 0.372 0.050 45 10 3.08 0.347 0.355 0.029 60 10 7.23 0.331 0.336 0.005 0 30 4.12 0.332 0.348 0.017 15 30 4.22 0.332 0.347 0.016 30 30 4.62 0.332 0.343 0.012 45 30 5.93 0.330 0.335 0.004 very slight color deviations at viewing angle after abrasion 60 30 10.38 0.326 0.329 0.008
Example 4
0 0 0.75 0.314 0.336 0.018 0 °, 100% layer (new) OK 15 0 0.77 0.317 0.334 0.015 30 0 0.96 0.326 0.330 0.005 45 0 1.85 0.338 0.333 0.007 very slight color deviations under the viewing angle 60 0 5.67 0.341 0.338 0.012 0 10 1.28 0.339 0.334 0.009 very slight color deviations after abrasion 15 10 1.35 0.341 0.334 0.010 30 10 1.67 0.345 0.335 0.014 45 10 2.79 0.348 0.339 0.019 60 10 6.93 0.345 0.342 0.018 0 30 3.58 0.319 0.310 0.024 15 30 3.69 0.321 0.312 0.021 30 30 4.13 0.325 0.318 0.014 45 30 5.48 0.329 0.326 0.008 very slight color deviations at viewing angle after abrasion 60 30 9.95 0.330 0.332 0.003
Example 5
0 0 0.51 0.308 0.334 0.023 0 °, 100% layer (new) OK 15 0 0.54 0.311 0.331 0.020 very slight color deviations at viewing angle 30 0 0.70 0.314 0.326 0.018 very slight color deviations at viewing angle 45 0 1 , 47 0.318 0.331 0.013 very slight color deviations under viewing angle 60 0 4.95 0.318 0.328 0.013 very slight color deviations under viewing angle 0 10 1.07 0.347 0.339 0.018 very slight color deviations after abrasion 15 10 1.14 0.344 0.336 0.014 very slight color deviations under viewing angle Abrasion 30 10 1.41 0.338 0.337 0.009 very small color deviations at the viewing angle after abrasion 45 10 2.36 0.332 0.336 0.005 very small color deviations at the viewing angle after abrasion 60 10 6.21 0.327 0.328 0.005 very small color deviations at the viewing angle after abrasion 0 30 3, 65 0.318 0.307 0.027 very slight color deviations after abrasion 15 30 3.73 0.319 0.311 0.023 very slight color deviations from the viewing angle after abrasion 30 30 4.06 0.323 0.321 0.013 very small color deviations at the viewing angle after abrasion 45 30 5.18 0.328 0.326 0.008 very small color deviations at the viewing angle after abrasion 60 30 9.50 0.331 0.324 0.009 very small color deviations at the viewing angle after abrasion
Example 6
0 0 0.48 0.329 0.329 0.003 0 °, 100% layer (new) OK 15 0 0.50 0.332 0.337 0.006 very low photopic reflectivity; very slight color deviations at viewing angle 30 0 0.67 0.328 0.334 0.004 very slight color deviations at viewing angle 45 0 1.46 0.333 0.330 0.003 very slight color deviations at viewing angle 60 0 5.06 0.337 0.328 0.006 very slight color deviations at viewing angle 0 10 1.15 0.354 0.355 0.033 very low color deviations after abrasion 15 10 1.22 0.349 0.350 0.026 very low photopic reflectivity; very small color deviations at the viewing angle after abrasion 30 10 1.50 0.341 0.344 0.016 very small color deviations at the viewing angle after abrasion 45 10 2.53 0.346 0.342 0.019 very small color deviations at the viewing angle after abrasion 60 10 6.63 0.346 0.335 0.016 very small color deviations at the viewing angle after abrasion 0 30 3.97 0.312 0.311 0.028 very small color deviations after abrasion 15 30 4.05 0.313 0.313 0.025 very low photopic reflectivity; very slight color deviations at the viewing angle after abrasion 30 30 4.41 0.320 0.323 0.013 very slight color deviations at the viewing angle after abrasion 45 30 5.71 0.336 0.336 0.007 very slight color deviations at the viewing angle after abrasion 60 30 10.45 0.344 0.336 0.014
[0073]. Examples 1 to 5 are anti-reflective coatings on a sapphire or Al2O3 substrate. Example 6 is a coating on a borosilicate glass which is sold under the trade name Borofloat.
The layer thicknesses of the individual layers of the anti-reflective coatings are as follows (in the order from the bottom layer to the top layer): Example 1: 35 nm, 35 nm, 23 nm, 78 nm, 86 nm. Example 2: 6.7 nm, 129 nm, 183 nm, 34 nm, 101 nm. Example 3: 20.5 nm, 32 nm, 25.6 nm, 133 nm, 79 nm. Example 4: 15.4 nm, 34 nm, 25 nm, 144 nm, 83 nm. Example 5: 38 nm, 13.9 nm, 105 nm, 18 nm, 26 nm, 100 nm, 80 nm. Example 6: 142 nm, 38 nm, 32 nm, 29 nm, 104 nm, 79 nm.
The transparent substrate of these examples is a substrate with a refractive index in the range from 1.7 to 1.8, for example a sapphire or aluminum oxide substrate.
The lowermost layer is in each case a layer with a low refractive index. In the coatings, layers with a low refractive index alternate with layers with a high refractive index. Preferably, even without being restricted to the above exemplary embodiments, two alternating materials with different refractive indices are used, so that the refractive index alternates between two values from layer to layer.
The low refractive index layers have, without limitation to the exemplary embodiments, according to one embodiment a refractive index at a wavelength of 550 nm in the range from 1.3 to 1.6, preferably 1.45 to 1.5, and the high refractive index layers have a refractive index at a Wavelength of 550 nm in the range from 1.8 to 2.3, preferably 1.95 to 2.1.
Features of the layer thicknesses of anti-reflective coatings according to the invention are described below. It is shown that multilayer anti-reflective coatings 5 according to the invention can be implemented with specific sequences of layer thicknesses. For this purpose, in the examples in FIGS. 5, 7 and 9, 81 different antireflective coatings according to the invention were considered on a substrate with a refractive index between 1.7 and 1.8, specifically on a sapphire substrate. The amount of anti-reflective coatings includes layer systems with five as well as seven layers.
5 shows the frequency distribution of the combined layer thicknesses of the two lowest layers, that is to say the layer with a low refractive index which is applied to the substrate, and the subsequent layer with a high refractive index. In the examples shown in FIG. 1, these would be layers 51 and 52. The layer thicknesses of the lowest pair, subdivided into classes, are plotted on the abscissa, and their frequency is plotted on the ordinate. As can be seen from FIG. 5, the layer thicknesses that occur range from approximately 10 nm to 360 nm. However, the layer thickness ranges (a) and (b) are from approximately 80 nm to 130 nm (range (a)) and from 240 nm range up to 280 nm (region (b)), except. The examples are anti-reflective coatings on sapphire substrates.
6 shows a corresponding distribution for anti-reflective coatings on a substrate with a low refractive index between 1.45 and 1.55, in particular a borosilicate glass substrate. The substrate has a refractive index of 1.47 at 550 nm. Here, too, there is a corresponding cut-out area “(a ')” of the layer thickness for the lowest pair of layers, within which there are no anti-reflective coatings with good optical properties with regard to invariance against abrasion of the top layer. This range extends from 65 nm to 120 nm.
Combined, the result for areas (a) and (a ') is an excluded wavelength range of 80 nm to 120 nm, which at most is little dependent on the refractive index of the substrate.
In FIG. 7, the frequency distribution of the distance between the third uppermost boundary surface and the surface, i.e. the distance between the third and fourth uppermost layer (in the example of FIG. 1, this would be the boundary between layers 52 and 53) for coatings depicted on sapphire. As can be seen, the distance can be in a wide range between 70 nm and 500 nm. However, ranges between 95 nm and 126 nm (range (c)) and between 374 nm and 480 nm (range (d)) are excluded.
8 shows a corresponding distribution for anti-reflective coatings according to the invention on borosilicate glass. Here, too, there are areas (c '), (d') corresponding to areas (c) and (d). The range (c ') is between 100 nm and 120 nm and thus similar to the range (c). Accordingly, according to one embodiment of the invention, the layer thickness range from 100 nm to 120 nm is excluded for the distance from the third uppermost interface, essentially independently of the refractive index of the substrate.
The other area (d ') is shifted to lower thicknesses than the area (d). The factor of the shift can be approximated very well by a factor (n / n (Al2O3)) <2> if a thickness interval is considered which is somewhat narrower than the entire recessed area. Here, n denotes the refractive index of the substrate used and n (Al2O3) the refractive index of a sapphire substrate, in particular n (Al2O3) = 1.76. This results in a recessed thickness range of 380 nm (n / n (Al2O3)) <2> to 470 nm (n / n (Al2O3)) <2>.
9 shows yet another typical criterion for anti-reflective coatings according to the invention. Here the frequency distribution of the difference in layer thicknesses of the top pair of layers and the second top pair of layers is shown, in other words the distribution of the term [(top layer + second from top layer) - (third from top layer + fourth from top layer)]. The difference can accordingly be in a wide range between -350 nm and +320 nm, with ranges from -250 nm to -150 nm (range (e)), from -50 nm to +10 nm (range (f)) and from +230 nm to +270 nm (area (g)) are excluded.
In the corresponding distribution of the difference in the layer thicknesses of the uppermost and second from the uppermost pair of layers shown in FIG. 10, an almost congruent, recessed area (g ') is shown. Accordingly, it is provided in a further development of the invention that, essentially regardless of the refractive index of the substrate, a range of +230 nm to +270 nm is excluded for the difference between the layer thicknesses of the top pair and the second top pair.Two examples of the layer thicknesses of anti-reflective coatings from the set of coatings from which the frequency distributions of FIGS. 5, 7, 9 were obtained are (in the order in each case from the bottom layer to the top layer): Example 7 : 8.8 nm, 30 nm, 7.1 nm, 116 nm, 87 nm. Example 8: 13.5 nm, 12.6 nm, 13.5 nm, 30 nm, 25 nm, 153 nm, 92 nm.
In the diagrams of FIGS. 6, 8 and 10, two further examples are identified with the following layer thicknesses (also in the order from the bottom layer to the top layer): Example 9: 155 nm, 30 nm, 30 nm, 122 nm Example 10: 25 nm, 15 nm, 147 nm, 13.5 nm, 10 nm, 77 nm.
The positions of the two examples in the frequency distributions of FIGS. 5, 7, 9 are marked with “(7)” or “(8)” and the positions of the examples in FIGS. 6, 8, 10 with “( 9) ", and" (10) "marked as dashed lines.
Without limitation to the specific exemplary embodiments, the invention thus provides, according to one aspect of the invention, a transparent element 1, comprising a transparent substrate 3 and on this substrate 1 a multilayer anti-reflective coating 5 which comprises at least four, in particular at least five layers , wherein layers with a high refractive index 51, 53 alternate with layers 50, 52, 54 with a lower refractive index, and wherein the layers 51, 53 with a higher refractive index preferably have a greater hardness than the layers 50, 52, 54 with a lower refractive index, and The top layer 60 of the multi-layer anti-reflective coating 5 is a layer with a lower refractive index, and at least one of the following features applies to the layer thicknesses of the layers 51-54: (i) the bottom pair of layers has a layer thickness in the range of 10 nm to 360 nm, with the exception of layer thicknesses in the range from 80 nm to 120 nm, (ii) the distance between the third The uppermost interface to the surface is between 70 nm and 500 nm, with at least one of the ranges between 100 nm and 120 nm and between 380 nm (n / n (Al2O3)) <2> to 470 nm (n / n (Al2O3) ) <2> is excluded, where n denotes the refractive index of the substrate and n (Al2O3) denotes a refractive index of 1.76, (iii) the difference in the layer thicknesses of the top pair of layers and the second top pair of layers is in a range between - 350 nm and +320 nm, with the exception of a range from +230 nm to +270 nm. In the case of a substrate with a refractive index in the range from 1.7 to 1.8, in particular a sapphire substrate, additional ranges from -250 nm to -150 nm can be used in a further development for the difference in layer thicknesses of the top pair of layers and the second top pair of layers and be excluded from -50 nm to +10 nm, corresponding to areas (e) and (f) in FIG. 9.
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 Range from 1.8 to 2.3, preferably 1.95 to 2.1 for the layers with a higher refractive index.
With the aid of the following figures, further features of anti-reflective coatings according to the invention are described using the two data sets of layer thicknesses for anti-reflective coatings on sapphire and borosilicate glass.
11 to 14 show four diagrams in which the layer thicknesses of the top layers for four different types of anti-reflective coatings according to the invention are plotted next to one another. The layer thickness in nanometers is plotted on the ordinate. The abscissa is a continuous index which numbers the various layer systems. 11 shows the layer thickness of the top layer for various five-layer anti-reflective coatings on sapphire. FIG. 12 shows the layer thicknesses for anti-reflective coatings according to the invention on sapphire with seven layers.
FIG. 13 shows the layer thicknesses of the top layer of four-layer anti-reflective coatings and FIG. 14 shows the layer thicknesses of the top layer for six-layer coatings, both on borosilicate glass as the substrate. 11 to 14 it can be seen that the layer thickness of the top layer is in a narrow range between 60 nm and 130 nm, as can be seen from a single example of the four-layer anti-reflective coatings on borosilicate glass with a significantly lower layer thickness, FIG. away. The thickness range is obviously essentially independent of the type of substrate or the number of layers of the anti-reflective coating. According to a further development of the invention, it is therefore provided that the top layer of the anti-reflective coating has the above-mentioned layer thickness in the range from 60 nm to 130 nm.
15 to 18 show diagrams in which the layer thicknesses of the lowermost high-index layer are plotted for different types of antireflective coatings according to the invention. The representation of the values corresponds to FIGS. 11 to 14. The lowermost high-index layer can be the lowermost or also the second lowermost layer of the anti-reflective coating 5. In the case of a substrate 3 with a high refractive index, the lowermost layer is preferably a layer with a lower refractive index and consequently the second lowermost layer is the lowermost layer with a high refractive index. In the case of a substrate with a low refractive index, such as a borosilicate glass substrate, the lowermost layer of the anti-reflective coating is preferably also the lowermost layer with a high refractive index. 15 shows the layer thicknesses of the lowermost layer with a high refractive index of various exemplary embodiments of five-layer anti-reflective coatings 5 on a sapphire substrate. 16 shows corresponding examples of seven-layer anti-reflective coatings 5 on a sapphire substrate. FIGS. 17 and 18 show the layer thicknesses of the lowermost high-index layer for four-layer (FIG. 17) and six-layer (FIG. 18) antireflective coatings on borosilicate glass as the substrate. Similar to the histogram in FIG. 5, areas are shown which are favorable for the invariance according to the invention with respect to abrasion and areas in which there are no examples of coatings according to the invention. In particular, a layer thickness range between 50 nm and 100 nm and a layer thickness range between 180 nm and 220 nm are excluded. Accordingly, the invention provides in a further development that the lowermost layer with a high refractive index has a layer thickness between 4 nm and 350 nm, a layer thickness in the range between 180 nm and 220 nm and / or in the range between 180 nm and 220 nm being excluded.
The embodiments of anti-reflective coatings 5 according to the invention explained above with reference to the examples in FIGS of the design, the options for selecting the layer thicknesses can be used. This significantly reduces the number of options and thus also the calculation effort. Accordingly, it is provided in a further development of the method that at least one of the anti-reflective coatings 5, 6, for which at least one of the parameters color of the residual reflection is calculated at 0 ° light angle of incidence and photopic reflectivity at 0 ° angle of incidence, is selected such that at least one of the the following conditions are met:the lowest pair of layers has a layer thickness in the range from 10 nm to 360 nm, with the exception of layer thicknesses in the range from 80 nm to 120 nm and from 225 nm to 280 nm,the distance between the third uppermost interface and the surface is between 70 nm and 500 nm, with at least one of the ranges between 100 nm and 120 nm and between 380 nm (n / n (Al2O3)) 2 to 470 nm (n / n (Al2O3)) <2> is excluded, where n denotes the refractive index of the substrate and n (Al2O3) denotes a refractive index of 1.76,the difference in the layer thicknesses of the top pair of layers and the second top pair of layers is in a range between -350 nm and +320 nm, with the exception of a range from +230 nm to +270 nmthe top layer of the anti-reflective coating has a layer thickness in the range from 60 nm to 130 nm,the lowermost layer with a high refractive index has a layer thickness between 4 nm and 350 nm, a layer thickness in the range between 180 nm and 220 nm and in the range between 180 nm and 220 nm being excluded.
The invention can be used wherever special requirements are placed on the mechanical properties of anti-reflective coatings. In addition to being used as watch glasses or magnifying glasses for watch glasses, the invention can also be used in the fields of architecture, consumer electronics and optical components. In the field of consumer electronics, the invention is particularly suitable for cover glasses for smartphones, notebooks and LCD displays.
The invention is not restricted 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-reflective coating can be applied to both sides of a disk-shaped substrate. The anti-reflective coatings can then also have different colors of the residual reflection, for example according to the examples in FIGS. 3 and 4.

权利要求:
Claims (19)
[1]
1. Process for the production of a transparent element (1) with the steps:- It is used for at least one pair of anti-reflective coatings (5, 6) which comprise at least four layers, layers (51, 53) with a high refractive index alternating with layers (50, 52, 54) with a lower refractive index, the Layers (51, 53) with a higher refractive index have a greater hardness than the layers (50, 52, 54) with a lower refractive index, and wherein a top layer (60) of the multi-layer anti-reflective coating (5) is a layer with a lower refractive index, taking into account the refractive index of a substrate (3) at least one of the parameters- Color of the residual reflection at a light incidence angle of 0 ° and- photopic reflectivity at a light incidence angle of 0 °calculated, whereby the two anti-reflective coatings differ only in terms of the layer thickness of the top layer (60), so that the layer thickness of an anti-reflective coating (6) is at least 10% or 10 nanometers compared to the layer thickness of the other anti-reflective coating ( 5) is reduced, and it is checked whether at least one of the conditions is met for both anti-reflective coatings (5, 6):- the color of the residual reflection at a 0 ° angle of incidence of light with a reduced layer thickness differs from the color of the residual reflection at a 0 ° angle of incidence of light with an undiminished layer thickness of the top layer (60) in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.05,- the photopic reflectivity at 0 ° light angle of incidence with reduced layer thickness of the top layer (60) differs from the photopic reflectivity at 0 ° light angle of incidence with undiminished layer thickness by no more than ΔR_ph = 1.5%, and for at least one further pair of anti-reflective coatings the parameters of the color of the residual reflection and the photopic reflectivity are calculated and at least one of the conditions is checked again if the condition is not met for the first pair of anti-reflective coatings, and an anti-reflective coating with a thicker top layer (60) from a Pair of anti-reflective coatings is selected which meets at least one of the conditions, and this anti-reflective coating (5) is deposited on the substrate (3).
[2]
2. The method according to claim 1, characterized in that a check is carried out under a plurality of pairs of anti-reflective coatings with regard to the conditions of the difference in the color of the residual reflection at 0 ° light incidence angle or the difference in photopic reflectivity at 0 ° light incidence angle and among the investigated Pairs of the anti-reflective coatings is selected for the deposition, in which the smallest difference in the color of the residual reflection is present at a light incidence angle of 0 ° and / or the smallest difference in the photopic reflectivity is present at a 0 ° angle of incidence of light, and then this anti-reflective coating is deposited.
[3]
3. The method according to claim 1 or 2, characterized in that the anti-reflective coating (5) is selected so that- a color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at a light incidence angle of 30 ° differs by no more than Δx = 0.05, Δy = 0.05, or- a color of the residual reflection of the two anti-reflective coatings (5, 6) of a pair in the CIE xyz color system at a light incidence angle of 45 ° differs by no more than Δx = 0.05, Δy = 0.05.
[4]
4. The method according to any one of claims 1 to 3, characterized in that at least one of the anti-reflective coatings (5, 6), for which at least one of the parameters color of the residual reflection is calculated at 0 ° light angle of incidence and photopic reflectivity under 0 ° light angle of incidence, so it is selected that at least one of the following conditions is met:- the bottom pair of layers as a whole has a layer thickness in the range from 10 nm to 360 nm, with the exception of layer thicknesses in the range from 80 nm to 120 nm and from 225 nm to 280 nm,- the distance from the third uppermost interface to the surface is between 70 nm and 500 nm, with at least one of the ranges between 100 nm and 120 nm and between 380 nm (nin (Al2O3)) <2> to 470 nm (n / n ( Al2O3)) <2> is excluded, where n denotes the refractive index of the substrate and n (Al2O3) denotes a refractive index of 1.76,The difference in the layer thicknesses of the top pair of layers as a whole and the second top pair of layers as a whole lies in a range between -350 nm and +320 nm, with the exception of a range from +230 nm to +270 nm- the top layer of the anti-reflective coating has a layer thickness in the range from 60 nm to 130 nm,- the lowest layer with a high refractive index has a layer thickness between 4 nm and 350 nm, with the exception of a layer thickness in the range between 180 nm and 220 nm.
[5]
5. Transparent element (1), produced by a method according to one of claims 1 to 4, comprising a transparent substrate (3) and on this substrate (3) a multi-layer anti-reflective coating (5) which comprises at least four layers, wherein layers (51, 53) with a high refractive index alternate with layers (50, 52, 54) with a lower refractive index, and the layers (51, 53) with a higher refractive index have a greater hardness than the layers (50, 52, 54) have a lower refractive index, and wherein a top layer (60) of the multilayer anti-reflective coating (5) is a layer with a lower refractive index, and wherein the layers (51-54) are selected for given refractive indices with regard to their thickness so that when a reduction the layer thickness of the top layer (60) by 10% or by 10 nanometers, depending on which of these two cases results in the lower remaining layer thickness, at least one of the following features applies:- a color of the residual reflection of the anti-reflective coating (5) at a light incidence angle of 0 ° with a reduced layer thickness of the top layer (60) does not differ from a color at a 0 ° angle of light incidence with an undiminished layer thickness of the top layer (60) in the CIE xyz color system more than Δx = 0.05, Δy = 0.05, preferably not more than Δx = 0.03, Δy = 0.03, particularly preferably not more than Δx = 0.02, Δy = 0.02,- A photopic reflectivity of the anti-reflective coating (5) at a light incidence angle of 0 ° with a reduced layer thickness of the top layer (60) differs from a photopic reflectivity at a 0 ° light angle of incidence with an undiminished layer thickness of the top layer (60) by no more than ΔR_ph = 1.5 %.
[6]
6. Transparent element (1) according to claim 5, characterized in that the layers (51-54) are selected for given refractive indices in terms of their thickness so that the color of the residual reflection of the anti-reflective coating (5) is at 30 ° angle of incidence 10% reduced layer thickness of the top layer (60) differs from the color of the residual reflection at a light incidence angle of 30 ° with the same layer thickness of the top layer (60) in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.05 .
[7]
7. Transparent element (1) according to claim 5, characterized in that the layers (51-54) are selected for given refractive indices in terms of their thickness so that the color of the residual reflection of the anti-reflective coating (5) is at 45 ° angle of incidence 10% reduced layer thickness of the top layer (60) differs from the color at a 45 ° angle of incidence of light with undiminished layer thickness of the top layer (60) in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.05.
[8]
8. Transparent element (1) according to claim 5, characterized in that the layers (51-54) are selected for given refractive indices with regard to their thickness so that when the layer thickness of the top layer (60) is reduced in such a way that the layer thickness according to the reduction is 0.9 times the original layer thickness, the photopic reflectivity of the anti-reflective coating (5) at 0 ° light incidence angle with unchanged layer thickness 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%.
[9]
9. Transparent element (1) according to claim 8, characterized by at least one of the following features:- The color of the residual reflection of the anti-reflective coating (5) at a light incidence angle of 0 ° with an undiminished layer thickness differs from the color of the residual reflection at a light incidence angle of 0 ° in the CIE xyz color system by no more than Δx = 0.05, Δy = 0.0 when the layer thickness is reduced the top layer (60) by 20%, preferably 30%, particularly preferably 40%,- The photopic reflectivity of the anti-reflective coating (5) at 0 ° light angle of incidence at 20%, preferably by 30%, particularly preferably 40% reduced layer thickness of the top layer (60) differs from the photopic reflectivity at 0 ° light angle of incidence with undiminished Layer thickness by no more than ΔR_ph = 1.5%,- the color of the residual reflection of the anti-reflective coating (5) at a 30 ° angle of incidence of light with the top layer (60) remaining undiminished differs from the color of the residual reflection at a 0 ° angle of incidence in the CIE xyz color system by no more than Δx = 0.02, Δy = 0.02,- the color of the residual reflection of the anti-reflective coating (5) at a 45 ° angle of incidence does not differ from the color of the residual reflection at a 0 ° angle of incidence by no more than Δx = 0.05, Δy = 0.05),- the photopic reflectivity of the anti-reflective coating (5) at an angle of incidence of light of 0 ° with the layer thickness of the top layer (60) remaining undiminished is less than 1.5%,- A maximum of the reflectivity of the anti-reflective coating (5) in the wavelength range between 450 nm and 700 nm is less than 1.5% at an angle of incidence of light at 0 ° with the layer thickness of the top layer (60) remaining the same,- An absolute amount of the difference between the photopic reflectivity of the anti-reflective coating (5) at a light incidence angle of 30 ° to the photopic reflectivity at a 0 ° angle of incidence of light with an undiminished layer thickness of the top layer (60) is less than 0.5%, preferably less than 0.3%, particularly preferred less than 0.1%,- An absolute amount of the difference between the photopic reflectivity of the anti-reflective coating (5) at 45 ° angle of incidence of light to the photopic reflectivity at 0 ° angle of incidence of light with undiminished layer thickness of the top layer (60) is absolutely less than 0.5%, preferably less than 0.3% in particular preferably less than 0.1%,- an average reflectivity of the anti-reflective coating (5), averaged in the wavelength range between 450 nm and 700 nm at a light incidence angle of 0 ° with the top layer (60) remaining undiminished, is less than 1.5%,- an absolute amount of the difference between the average reflectivities of the anti-reflective coating (5) at a light incidence angle of 30 ° and an angle of light incidence of 0 ° with the top layer (60) remaining undiminished, averaged in the wavelength range between 450 nm and 700 nm, is absolutely less than 0, 5%, preferably less than 0.3%, particularly preferably less than 0.1%,- An absolute amount of the difference between the average reflectivities of the anti-reflective coating (5) at a 45 ° angle of incidence of light and at an angle of incidence of light at 0 ° with the layer thickness of the top layer (60) remaining the same, 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%,- An absolute amount of the difference between the maxima of the reflectivities of the antireflective coating (5) in the wavelength range from 450 nm to 700 nm at a light incidence angle of 30 ° and an angle of incidence of light at 0 ° with an undiminished layer thickness of the top layer (60) is less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1%,- A difference in the absolute reflectivities of the anti-reflective coating (5) at 45 ° angle of incidence of light and under 0 ° angle of incidence of light with an undiminished layer thickness of the top layer (60) is absolutely less than 0.5%, preferably less than 0.3%, particularly preferably less than 0.1 %.
[10]
10. Transparent element (1) according to claim 9, characterized by at least one of the features:- the photopic reflectivity of the anti-reflective coating (5) at an angle of incidence of light of 0 ° with the layer thickness of the top layer (60) remaining undiminished is less than 1%, preferably less than 0.8%,- the absolute amount of the difference between the average reflectivity of the anti-reflective coating (5) in the wavelength range between 450 nm and 700 nm at a light incidence angle of 30 ° with the layer thickness of the top layer (60) remaining the same as the average reflectivity in the wavelength range between 450 nm and 700 nm at 0 ° Angle of incidence of light is less than 0.1%,- the difference between the photopic reflectivity of the anti-reflective coating (5) or the average reflectivity at an angle of incidence of light of 45 ° with an undiminished layer thickness of the top layer (60) and the photopic reflectivity at an angle of incidence of light of 0 ° is absolutely less than 0.2%,- The average reflectivity of the anti-reflective coating (5), averaged in the range between 450 nm and 700 nm at an angle of incidence of light at 0 ° with an undiminished layer thickness of the top layer (60), is less than 1.0%.
[11]
11. Transparent element (1) according to one of claims 5 to 10, characterized in that the substrate (3) is a sapphire substrate.
[12]
12. Transparent element (1) according to one of claims 5 to 11, characterized in that the substrate (3) has a refractive index above 1.65 and the anti-reflective coating (5) has a sequence of at least five alternating layers (50 - 54) with a lower and a higher refractive index, the lowermost layer (50) being a layer with a lower refractive index.
[13]
13. Transparent element according to claim 12, characterized in that for the layer thicknesses d1, d2, d3, d4, d5 of the layers (50, 51, 52, 53, 54) of the anti-reflective coating (5) according to a first case applies :- the thickness d1 of the first layer on the substrate (3), i.e. the bottom layer (50), is 5 nm to 60 nm,- the thickness d2 of the second layer (51) is 5 nm - 50 nm,- the thickness d3 of the third layer (52): 10 nm to 200 nm,- the thickness d4 of the fourth layer (53) is 100 nm to 200 nm,- the thickness d5 of the fifth, uppermost layer (54) is 70 nm to 120 nm,or according to a second case:- the thickness d1 of the first layer on the substrate (3), i.e. the bottom layer (50), is 5 nm to 60 nm,- the thickness d2 of the second layer (51) is 30 nm to 200 nm,- the thickness d3 of the third layer (52): 10 nm to 200 nm,- the thickness d4 of the fourth layer (53) is 150 nm to 300 nm,- the thickness d5 of the fifth, uppermost layer (54) is 70 nm to 120 nm,where in both cases the following applies to the layer thicknesses:D = 85nm + 1.7 * d1 + 1.1 * d2 - 0.9 * d3 + 0.0138 * (d3-60nm) <2>, where D is the value of the layer thickness d4 of the fourth layer (53) with a maximum deviation of ± 15%, preferably indicates a maximum of ± 10%, particularly preferably a maximum of ± 5%.
[14]
14. Transparent element (1) according to one of claims 5 to 13, characterized by layers (51, 53) with a high refractive index made of at least one of the materials silicon nitride Si3N4, aluminum oxide Al2O3, aluminum nitride AlN, or aluminum silicon nitride AlwSixNyOz.
[15]
15. Transparent element (1) according to one of claims 5 to 14, characterized in that the anti-reflective coating (5) has a maximum of twelve, preferably a maximum of ten layers.
[16]
16. Transparent element (1) according to one of claims 1 to 15, wherein at a wavelength of 550 nm the layers with a lower refractive index have a refractive index in the range from 1.3 to 1.6 and the layers with a high refractive index have a refractive index in the range of 1.8 to 2.3, characterized in that at least one of the following features applies to the layer thicknesses of the layers (51 - 54):(i) the bottom pair of layers as a whole has a layer thickness in the range from 10 nm to 360 nm, with the exception of layer thicknesses in the range from 80 nm to 120 nm and from 225 nm to 280 nm,(ii) the distance from the third uppermost interface to the surface is between 70 nm and 500 nm, with at least one of the ranges between 100 nm and 120 nm and between 380 nm (n / n (Al2O3)) <2> to 470 nm n / n (Al2O3)) <2> is excluded, where n denotes the refractive index of the substrate and n (Al2O3) denotes a refractive index of 1.76,(iii) the difference in the layer thicknesses of the top pair of layers as a whole and of the second top pair of layers as a whole is in a range between -350 nm and +320 nm, with the exception of a range from +230 nm to +270 nm.
[17]
17. Transparent element (1) according to one of claims 5 to 16, characterized in that the top layer (60) of the anti-reflective coating has a layer thickness in the range from 60 nm to 130 nm.
[18]
18. Transparent element (1) according to one of claims 5 to 17, characterized in that the lowermost layer with a high refractive index has a layer thickness between 4 nm and 350 nm, a layer thickness in the range between 180 nm and 220 nm being excluded.
[19]
19. Transparent element (1) according to one of claims 5 to 18, designed as a watch glass or a magnifying glass of a watch glass.

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同族专利:

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法律状态:
2022-01-14| PK| Correction|Free format text: BERICHTIGUNG |

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2022-02-28| PK| Correction|Free format text: BERICHTIGUNG B8 |

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