Optical component with scratch resistant anti-reflection coating and method for producing same

Abstract

Abstract: The invention is based on the object of providing an optical component for use in a plurality of spectral ranges, in particular in the infrared range, which component withstands harsh environmental conditions for a long time. For this purpose, an optical component (10) is provided comprising a substrate (1) that is partially transparent in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and from 7500 nm to 12,000 nm, provided with a layer stack (2) that defines an anti-reflection coating comprising at least three layers, wherein the successive layers of the layer stack (2) are made of at least three different materials or material combinations, wherein at least 50 % of the total thickness of the layer stack (2) are oxide layers and / or at least half the number of layers of the layer stack (2) are oxide layers, and wherein the substrate (1) with the layer stack (2) exhibits a transmittance of at least 80 % at a wavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and from 7500 nm to 12,000 nm. (FIG. 1) Abstract: 2020281146 04 Dec 2020 1 / 3 20 20 28 11 46 0 4 D ec 2 02 02020281146 04 Dec 2020 10 Fig. 2 6 '9 20 1 / 3 2 1

Description

10 range and / or at a laser wavelength in the near infrared range between 1000 nm and 1600 nm, an IR material has been found to be a particularly suitable substrate according to the present disclosure, preferably an IR glass (chalcogenide glasses "IRG", e.g. IRG22, IRG24, IRG25, IRG26, or IRG27, manufactured by SCHOTT AG) or a (mono- or multi-) crystalline material that comprises a zinc chalcogenide, particularly preferably zinc sulfide (ZnS) or zinc selenide (ZnSe). 15 Materials having relatively high refractive indices are associated with strong surface reflectance, therefore these substrates are provided with a complex anti-reflection coating, since the latter should be effective in the specified spectral ranges. 20 Furthermore, for the lowermost layer, i.e. the first layer of the layer stack or the layer that is in contact with the substrate, a material is preferably selected which exhibits particularly good adhesion properties or at least better adhesion properties on the substrate than in particular the material of the first type. The main purpose of this layer is to promote adhesion between the substrate and the coating. The layer thus preferably fulfills a chemical-mechanical purpose and 25 does not primarily need to fulfill an optical purpose. In a special embodiment of the optical component with improved layer adhesion, the adhesion promoting layer preferably consists of magnesium oxide (MgO), yttrium oxide (Y2O3), DLC (diamond-like carbon), or mixtures thereof. Thus, in particular mixtures of MgO with MgxAlyOz, 30 with MgxScyOz, with AlxScyOz can also be considered as an adhesion promoting layer. Such an adhesion promoting layer exhibits particularly good adhesion properties on the substrate made of 2020281146   10 Sep 2026 zinc sulfide (ZnS) or zinc selenide, and can be combined particularly well with the aforementioned further layers of the layer stack. For an optical component with improved layer adhesion, the substrate surface is preferably 5 modified by ion implantation with copper ions (Cu+ or Cu2+) to form an adhesion promoting layer. In a further special embodiment of the optical component with improved layer adhesion, the density of reactive OH- groups is increased on the substrate surface by alkaline etching (e.g. using KOH). 10 In a particular embodiment of the optical component, the lowermost layer of the layer stack, or the adhesion promoting layer, preferably comprises magnesium oxide (MgO), or yttrium oxide (Y2O3), or hafnium oxide (HfO2), or aluminum oxide (Al2O3), and at least one further layer of the layer stack preferably comprises scandium oxide (Sc2O3) or hafnium oxide (HfO2), and the uppermost 15 layer advantageously comprises aluminum oxide (Al2O3). Depending on the relevance of the optical properties, the adhesion promoting layer can have the thinnest layer thickness of the layer stack and / or may have a layer thickness in the range of a few nanometers, preferably in the range from 5 nm to 50 nm, in particular 5 nm to 30 nm. 20 The adhesion promoting layer can be kept thin enough to have no or only little optical influence on the reflection properties of the layer stack. With a respective greater layer thickness, the adhesion promoting layer may at the same time also define an optically effective component of the layer stack, which contributes to the anti-25 reflection effect. In view of scratch and climate resistance, the uppermost layer of the layer stack preferably has a layer thickness in the range from 5 nm to 500 nm. In a particularly advantageous embodiment, the optical component has a layer stack comprising 30 between five and thirty layers in total. 2020281146   10 Sep 2026 It has been found that the optical component embodying the present disclosure preferably shows no visible signs of scratches on the surface after a windshield wiper test in compliance with the TS1888 standard, and that preferably the amount of surface defects according to ISO10110 is reduced by at least 20 % in comparison to an optical component with a fluoride layer as the 5 uppermost layer, and / or that it exhibits a haze of less than 30 % after a "sand & dust" test in compliance with MIL-STD-810G method 510.5, and according to ASTM D 1003-00 a component is to be regarded as transparent if haze is less than 30 %. With regard to the method for producing an optical component according to the present 10 disclosure with an anti-reflection coating, a layer stack consisting of a plurality of successive layers of different materials is applied on a substrate to form an anti-reflection coating, and the layers of the layer stack are preferably successively deposited from at least three different materials or material combinations, wherein at least 50 % of the total thickness of the layer stack are oxide layers and / or at least half the number of layers of the layer stack are oxide layers, and 15 wherein the substrate with the layer stack exhibits a transmittance of at least 80 % at a wavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and from 7500 nm to 12,000 nm. To produce the optical component embodying the present disclosure, the adhesion promoting 20 layer described above is preferably deposited directly on the substrate described above. In a particular embodiment of the method for producing the optical component according to the present disclosure, the layer stack is preferably produced as described above. 25 For coating the optical component embodying the present disclosure, the uppermost layer may in particular be applied by a technique selected from the group consisting of ion plating, ion implantation, ion beam-assisted or plasma-assisted deposition (advanced plasma deposition), magnetron sputtering, ion beam sputtering, cathodic arc deposition, and atomic layer deposition. Especially ion or plasma assistance is advantageous in order to increase the density, hardness 30 and compressive stress of the uppermost layer and thus make it more resistant to abrasion. 2020281146   10 Sep 2026 Also, the uppermost layer of the layer stack of the optical component according to the present disclosure may be deposited by a different technique than the other layers of the layer stack. For example, if more than one layer of the layer stack consists of the material the uppermost layer is made of, it is also possible for the uppermost layer to be deposited by one technique, and that the 5 other or further layers of the same material are deposited by a different technique. This is particularly advantageous if a technique is used to increase the density, hardness, or compressive stress of the uppermost layer, and if this technique is not compatible with another layer material. 10 In one particular embodiment of the present disclosure, the layer stack with the exception of the uppermost layer is deposited by classic electron beam vapor deposition, and for the uppermost layer an ion or plasma process is used additionally. In this case, it may be advantageous to initially start the deposition of the uppermost layer without 15 the additional ion or plasma process in order to protect the underlying material of the second uppermost layer from the ion or plasma process. Preferably, the uppermost layer of the layer stack is applied in the form of two sub-layers, the second sub-layer being applied without an assisting plasma or ion process and the first sub-layer 20 being applied with an assisting plasma or ion process. As a result, the uppermost layer can be divided into two sub-layers made of the same material, which for example have a similar refractive index, but not the same. The portion which is deposited with the additional ion or plasma process preferably has a somewhat higher refractive index than the portion which is deposited without the additional process. 25 In order to improve adhesion of the layer stack to the surface of the substrate, the surface of the substrate is preferably modified by at least one technique selected from the group consisting of ion implantation, etching, leaching, wet chemical ion exchange, before the layer stack is deposited. 2020281146   10 Sep 2026 In a particularly advantageous embodiment, a chalcogenide substrate, preferably a sulfide or selenide, is used as the substrate, and the surface thereof is preferably modified by alkaline etching, for example using zinc hydroxide in the case of a zinc sulfide substrate. 5 According to the disclosure, the optical component is used as a cover glass and protective glass or window for optical and optronic components such as cameras, in particular surveillance cameras, in rangefinders and in periscopes, which can be used in the infrared range and preferably also in the visible spectral range. Thus, potential application fields include aircraft, aerial vehicles, track vehicles, wheeled vehicles, motor vehicles, in particular also unmanned 10 aerial vehicles such as drones or missiles or rockets (supersonic or subsonic) or gimbaled systems. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or 15 group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Specific embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings, in which the same reference numerals denote the same 20 elements. Brief Description of the Drawings In the drawings: 25 FIG. 1 shows a schematic view of the optical component embodying the present disclosure comprising a substrate and a layer stack; FIG. 2 shows a schematic view of the optical component comprising a substrate and a layer stack which includes an adhesion promoting layer as the lowermost layer directly on the substrate; 30 FIG. 3 shows a schematic view of a specific configuration of the layer stack of the optical component of FIG. 1 or FIG. 2; 2020281146   10 Sep 2026 FIG. 4 shows a graph of the transmittance of a non-coated substrate made of ZnS and of three optical components comprising a ZnS substrate and, applied thereon, layer stacks of three different designs of an anti-reflection coating as a function of wavelength in the infrared range from 6000 nm to 15,000 nm; and 5 FIG. 5 shows a graph of reflectance of a non-coated substrate made of ZnS, and of three optical components comprising a ZnS substrate and, applied thereon, layer stacks of three different designs of an anti-reflection coating as a function of wavelength in the visible range from 400 nm to 800 nm; FIG. 6 shows a diagram of the increase in the haze value of the three optical components 10               during an abrasion test. FIG. 1 shows a schematic sectional view of the optical component 10 embodying the present disclosure comprising a substrate 1 which is partially transparent in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and 7500 nm to 12,000 nm, and provided thereon a 15 layer stack 2 which defines an anti-reflection coating comprising at least three layers 20, the successive layers 20 of the layer stack 2 being made of at least three different materials or material combinations, wherein at least 50 % of the total layer thickness of the layer stack 2 consists of oxide layers and / or at least half the number of layers in the layer stack 2 are oxide layers, and wherein the substrate 1 with the layer stack 2 exhibits a transmittance of at least 80 % 20 at a wavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and 7500 nm to 12,000 nm. For the sake of clarity, only one of the layers is designated with the reference number 20 in the figures. In a variant of the optical component 10, the substrate 1 with the layer stack 2 can additionally 25 have a transmittance of at least 80 % at a wavelength in the visible spectral range and / or in the near infrared range from 1000 nm to 1600 nm. Substrates exhibiting high transmittance in the infrared spectral range in particular include chalcogenide substrates, such as sulfides or selenides, in particular zinc chalcogenide. Zinc sulfide is particularly preferred as the substrate material or at least as a constituent thereof. FIG. 2 shows a schematic view of the optical component 10 embodying the present disclosure, with an adhesion promoting layer 6 forming the lowermost layer 9 of the layer stack 2, which is 2020281146   10 Sep 2026 preferably applied directly on the substrate 1. Layers particularly suitable as adhesion promoters include layers that contain a material selected from the group consisting of aluminum oxide (Al2O3), magnesium oxide (MgO), yttrium oxide (Y2O3), DLC (diamond-like carbon), hafnium oxide (HfO2), and / or mixtures thereof. 5 In a preferred embodiment of the optical component 10, the layer stack 2 according to FIG. 3 includes at least one oxide layer of a first type 4 and at least one oxide layer of a second type 3, wherein a layer of the first type 4 has a higher refractive index than a layer of the second type 3, and wherein an uppermost layer 7 and a second uppermost layer 8 of the layer stack 2 are 10 provided, wherein the uppermost layer 7 is an oxide layer of the second type 3 or an oxide or fluoride layer of a third type 5, and the second uppermost layer 8 is a layer of the first type 4. The uppermost layer 7 as the final layer at the same time closes off the layer stack 2 to the environment. With the aforementioned configuration, the anti-reflection properties have been found to be particularly good. For greater hardness or abrasion resistance, the uppermost layer 7 15 of the layer stack 2 is preferably an oxide layer. For a particularly scratch-resistant and climate-resistant optical component 10, the following variations of layers 20 of the layer stack 2 are preferred: The lowermost layer 9 preferably comprises a material different from the materials of the 20 alternating layer system, or an adhesion promoting layer 6, preferably aluminum oxide (Al2O3), magnesium oxide (MgO), yttrium oxide (Y2O3), DLC (diamond-like carbon), or hafnium oxide (HfO2). Thereon preferably follows an alternating layer system with alternating layers comprising oxide layers of the first type 4, preferably made of scandium oxide (Sc2O3) or hafnium oxide (HfO2), and at least two oxide or fluoride layers of the third type 5, preferably made of aluminum 25 oxide (Al2O3), yttrium oxide (Y2O3), or yttrium fluoride (YF3), and the alternating layer system can start with an oxide layer of the first type 4 or with an oxide or fluoride layer of the third type 5. The second uppermost layer 8 of the layer stack 2 is preferably a layer of the first type 4, preferably made of scandium oxide (Sc2O3) or hafnium oxide (HfO2). The uppermost layer 7 of the layer stack 2 is preferably an oxide layer of the second type 3, 30 which in particular comprises hafnium oxide (HfO2), scandium oxide (Sc2O3), yttrium oxide (Y2O3), or most preferably aluminum oxide (Al2O3). Alternatively, the uppermost layer 7 of the layer stack 2020281146   10 Sep 2026 2 is preferably an oxide or fluoride layer of the third type 5, preferably made of aluminum oxide (Al2O3), yttrium oxide (Y2O3), or yttrium fluoride (YF3). In a special embodiment of the optical component 10, the lowermost layer 9 of the layer stack 2 5 preferably comprises magnesium oxide (MgO) or yttrium oxide (Y2O3) as the adhesion promoting layer 6, at least one further layer of the layer stack 2 preferably comprises scandium oxide (Sc2O3) or hafnium oxide (HfO2), and the uppermost layer 7 advantageously comprises aluminum oxide (Al2O3). 10 Preferably, for good anti-reflection properties in multiple wavelength ranges, more than three layers of the layer stack 2 are useful. In this case, it is preferred to form the layer stack 2 as an alternating layer system with alternating layers comprising oxide layers of the first type 4 and at least two oxide or fluoride layers of the third type 5, with the layers of the third type 5 having a refractive index that is lower than the 15 refractive index of the uppermost layer 7. In an alternating layer system according to the present disclosure, the layer materials alternate, but usually not or not necessarily the layer thicknesses. In an exemplary optical component 10 according to the present disclosure referred to as Design 2, the layer stack 2 comprises nine layers in total, which corresponds to a preferred embodiment 20 of the anti-reflection coating in terms of scratch resistance and the anti-reflection effect. More generally, without being limited to specific examples, it is contemplated for an embodiment of the present disclosure according to Design 2 that the substrate 1 is made of zinc sulfide (ZnS) or zinc selenide (ZnSe), and that, deposited thereon, the lowermost layer 9 of the nine-layer stack 2 is made of yttrium oxide (Y2O3), preferably with a layer thickness of 30 nm. This lowermost layer 25     9 of the layer stack 2 is preferably an adhesion promoting layer 6. It is preferably followed by an alternating layer system with alternating layers comprising oxide layers of the first type 4 and at least two oxide or fluoride layers of the third type 5, and the layers of the third type 5 have a refractive index that is lower than the refractive index of the uppermost layer 7. According to Design 2, this alternating layer system with alternating layers consists of four oxide layers of the 30 first type 4 in the form of scandium oxide (Sc2O3) and of three fluoride layers of the third type 5 in the form of yttrium fluoride (YF3), and of an uppermost layer 7 made of aluminum oxide (Al2O3), with the refractive index of yttrium fluoride (YF3) being lower than that of aluminum oxide (Al2O3). 2020281146   10 Sep 2026 Thus, in Design 2, the material of the lowermost layer 9 is different from the materials of the alternating layer system. On a substrate made of zinc sulfide (ZnS) with a refractive index of 2.24, the following layers are 5 used in the layer stack for a coating according to the Design 2 of the present disclosure, with a total of four different materials: Design 2: Layers of layer stack Material Layer thickness (nm) Refractive index Uppermost layer: Type 2 / Type 3 Al2O3 80 1.765 Second uppermost layer: Type 1 SC2O3 700 1.99 Type 3 layer YF3 60 1.47 Type 1 layer SC2O3 80 1.99 Type 3 layer YF3 30 1.47 Type 1 layer SC2O3 50 1.99 Type 3 layer YF3 500 1.47 Type 1 layer SC2O3 50 1.99 Lowermost layer / adhesion promoter Y2O3 30 1.93 10 For greater hardness or abrasion resistance, the uppermost layer 7 of the layer stack 2 is preferably an oxide layer. With regard to the optical quality in terms of low reflectance and high transmittance of at least 80 % at a wavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and from 7500 nm to 12,000 nm, the uppermost layer 7 of the layer stack 2 has a refractive index 15 of preferably equal to or most preferably less than 1.95. A higher abrasion resistance of a multilayer coating can also be achieved if the second uppermost layer 8 is harder or more stable than the uppermost layer 7 of the layer stack 2, in particular if it has a higher refractive index. This is also the case with Design 2, since the second 20 uppermost layer 8 comprises scandium oxide which has a higher refractive index than the 2020281146   10 Sep 2026 aluminum oxide of the uppermost layer 7 of the layer stack 2, whereby the final, uppermost layer 7 is given sufficient stability by the underlying harder layer without imparting excessive reflectance to the entire optical component 10 due to the lower refractive index of the uppermost layer 7. As a result, the optical component 10 according to the present disclosure is both very 5 abrasion-resistant and anti-reflective. The refractive index of the uppermost layer 7 is lower than the refractive index of the second uppermost layer 8. Thereby, an anti-reflection effect is achieved on the one hand, and on the other hand high mechanical resistance. 10 The scratch resistance therefore not only depends on the properties of the surface, i.e. of the uppermost layer of the layer stack, but also on the hardness or stability of the underlying materials and layers that support the layer on the surface. The reverse phenomenon is more commonly known as the "chocolate-coated marshmallow" effect, where an inherently relatively hard surface (chocolate) can break down into underlying softer material (sugar foam). In order to 15 counteract this effect where the uppermost layer breaks into the second uppermost layer, it is therefore advantageous if the uppermost layer is made of a softer material than the second uppermost layer and if also layers there below comprise an alternation of softer and harder layers or layers with alternately lower and higher refractive indices. 20 As an alternative to Design 2, the layer stack 2 may also comprise an alternating layer system comprising layers with alternating refractive indices, in which the uppermost layer 7 of the layer stack 2 forms part of the alternating layer system. For example, the layer stack 2 may consist of only three different materials, for the sake of simplicity. 25 More generally, without being limited to specific examples, it is contemplated for a corresponding embodiment of the present disclosure according to Design 1 that the substrate 1 is made of zinc sulfide (ZnS) or zinc selenide (ZnSe), and that the lowermost layer 9 of an eight-layer stack 2 is made of yttrium oxide (Y2O3), preferably with a layer thickness of 20 nm. This lowermost layer 9 of the layer stack 2 is preferably an adhesion promoting layer 6 or preferably at least a layer 30 made of a material that is different from the materials of the alternating layer system. It is preferably followed by an alternating layer system in which the uppermost layer 7 of the layer 2020281146   10 Sep 2026 stack 2 forms part of the alternating layer system and has a lower refractive index than the second uppermost layer 8, and all the layers 20 of layer stack 2 are pure oxide layers. According to Design 1, this alternating layer system comprises alternating layers made of four 5 oxide layers of the third type 5 in the form of aluminum oxide (Al2O3) and three oxide layers of the first type 4 in the form of hafnium oxide (HfO2), with the refractive index of aluminum oxide (Al2O3) as the uppermost layer 7 being lower than that of the second uppermost layer 8 in the form of hafnium oxide (HfO2). This is advantageous because the aforementioned oxides provide a combination of high abrasion 10 resistance and a medium to high refractive index. In Design 1, again, the material of the lowest layer 9 is different from the materials of the alternating layer system. On a substrate made of zinc sulfide (ZnS) with a refractive index of 2.24, the following layers are 15 used in the layer stack as layer materials for a coating according to the Design 1 of the present disclosure, at a wavelength of 1000 nm in each case, with a total of three different materials in the layer stack: Design 1: Layers of layer stack Material Layer thickness (nm) Refractive index Uppermost layer: Type 2 / Type 3 Al2O3 75 1.765 Second uppermost layer: Type 1 HfO2 100 2.01 Type 3 layer AlA 1000 1.765 Type 1 layer HfO2 80 2.01 Type 3 layer Al2O3 50 1.765 Type 1 layer HfO2 50 2.01 Type 3 layer Al2O3 20 1.765 Lowermost layer / adhesion promoter Y2O3 30 1.93 2020281146   10 Sep 2026 For greater hardness or abrasion resistance, the uppermost layer 7 of the layer stack 2 is preferably an oxide layer. Without being limited to the example of Design 1, all layers 20 of layer stack 2 may be oxide 5 layers. This has the advantage of simpler manufacturing on the one hand and high abrasion resistance on the other. With regard to the optical quality in terms of low reflectance and high transmittance of at least 80 % at a wavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm 10 and from 7500 nm to 12,000 nm, the uppermost layer of the layer stack has a refractive index of preferably equal to or most preferably less than 1.95. For good anti-reflection properties, it makes sense to apply a relatively low-index layer as the uppermost layer. Higher abrasion resistance of a multilayer coating can also be achieved if the second uppermost 15 layer 8 is harder or more stable, in particular, if it has a higher refractive index than the uppermost layer 7 of the layer stack 2. This is in particular the case with Design 1, since the second uppermost layer 8 comprises hafnium oxide which has a higher refractive index than the aluminum oxide of the overlying uppermost layer 7 of the layer stack 2, so that the final, uppermost layer 7 is given sufficient stability by the harder layer there below, without causing the 20 entire optical component 10 to be excessively reflective due to the lower refractive index of the uppermost layer 7. Thus, the optical component 10 according to the present disclosure is both abrasion-resistant and anti-reflective. The refractive index of the uppermost layer 7 is lower than the refractive index of the second 25 uppermost layer 8. Thereby, an anti-reflection effect is achieved on the one hand, and on the other hand high mechanical resistance. One reason for the targeted selection of the layer materials is the combination of refractive indices and the hardness of these materials. Increased hardness of the uppermost layer 7 may 30 also be produced by applying the uppermost layer 7 using special deposition processes so that they become particularly hard. 2020281146   10 Sep 2026 For this purpose, the following techniques can be considered: ion plating, ion implantation, ion beam-assisted or plasma-assisted deposition (advanced plasma deposition), magnetron sputtering, ion beam sputtering, cathodic arc deposition, and atomic layer deposition. 5 It is not necessary to use the same technique for applying all the layers 20 of the layer stack. Different techniques can be combined with each other. For example, according to one embodiment, all layers except for the uppermost layer 7 can be deposited thermally by vapor deposition, while the uppermost layer 7 is applied by a sputter deposition process. Switching the coating technique is still economically efficient if a switch only has to be made for the uppermost 10 layer. Especially ion or plasma assist is advantageous in order to increase density, hardness, and compressive stress of the uppermost layer and to make it more resistant to abrasion. Below, three optical components 10 with different layer systems A, B, and C according to the present disclosure will be compared with regard to their optical properties and their abrasion 15 resistance. Layer system A comprises the same sequence of layers, with the difference that the lowermost layer 9 is not a Y2O3 layer, but an HfO2 layer. In the case of layer system B, which is otherwise identical, the lowermost layer 9 that is made of Y2O3 in Design 2 is replaced by a layer made of Al2O3 of the same thickness. Layer system C corresponds to Design 2, so it has a Y2O3 layer as the lowermost layer 9. All the layer stacks were applied on a ZnS substrate 1. The 20 examined components 10 with layer systems A, B, C therefore only differ in the composition of the adhesion promoting layer 6 of the layer stack 2. FIG. 4 shows the transmittance of a non-coated ZnS substrate and of three optical components comprising a ZnS substrate and a layer stack as an anti-reflection coating, thus forming the layer 25 systems A, B and C explained above, as a function of wavelength in the infrared range from 6000 nm to 15,000 nm. The transmittance profile of a non-coated substrate is shown by the graph ZnS drawn with a continuous line. Transmittance is about 75 % and constant for a wavelength from about 6000 nm 30 to 10,500 nm, then drops to reach 70 % at about 11,300 nm, then increases to about 72 % in a section up to 11,600 nm, and then the transmittance drops again, in particular to reach 50 % at a wavelength of 13,500 nm. 2020281146   10 Sep 2026 As can be seen from the diagram, all three optical components with layer systems A, B, C exhibit a transmittance of well over 80 % at a wavelength of 8500 nm, i.e. in the wavelength range from 7500 nm to 12,000 nm. The transmittance profile of a ZnS substrate coated according to the present disclosure and comprising an HfO2 adhesion promoting layer is shown by the long- 5 dashed curve A. It increases with increasing wavelength from 75 % at a wavelength of 6500 nm to 80 % at around 7000 nm and to almost 90 % at a wavelength of about 8500 nm, and then falls again to below 80 % at a wavelength of approx. 9300 nm. The transmittance profile of a further ZnS substrate coated embodying the present disclosure is shown by short-dashed curve B. Layer system B corresponds to Design 2, except for comprising an Al2O3 layer as the lowermost layer 10 or as the adhesion promoting layer. Transmittance increases with increasing wavelength from more than 80 % at a wavelength of 6500 nm to 95 % at a wavelength of around 8500 nm, and then falls again to a transmittance of 80 % and below for a wavelength of 10,500 nm and beyond. The transmittance profile of yet another ZnS substrate coated according to the present disclosure 15 is shown by dotted curve C. It increases with increasing wavelength from 75 % at a wavelength of 6500 nm to 95 % at a wavelength of about 9500 nm, and then falls again to a transmittance of 80 % and below for a wavelength of 12,500 and beyond. In the wavelength range shown, layer system C according to Design 2 exhibits the highest transmittance over a widest infrared spectral range. 20 FIG. 5 shows the reflectance of a non-coated ZnS substrate in comparison with the three optical components comprising a ZnS substrate and, deposited thereon, layer stacks in the form of an anti-reflection coating defining the layer systems A, B, C, as a function of wavelength in the visible range from 400 nm to 800 nm. The reflectance profile of the non-coated substrate is 25 shown by the curve "ZnS" drawn in a continuous line. Reflection is constant at a wavelength from 400 nm to 800 nm with a reflectance of slightly below 30 %. The reflectance profiles of the optical components with layer systems A, B, and C are similar to one another. From 400 nm to approx. 430 nm, reflectance falls from 55 % to below 10 %. In all 30 three layer systems, reflectance remains below 20 % for wavelengths of up to 800 nm. 2020281146   10 Sep 2026 The optical components with the layer systems A, B, C were subjected to two standard tests to verify their scratch resistance or abrasion resistance. The first standard test is known as the Bayer test according to ASTM F735-11, TABER. The abrasive medium used in this case was silica sand which has the following properties: Grading 5 / 9 Roundness 0.6+ Sphericity 0.6+ Hardness 7.0 S.G. 2.65 Loss on ignition 0.1 MP 2800° / 3100° Color brown / white pH 6.9 - 7.0 The typical chemical composition of the silica sand used is as follows, in percent by weight: SiO2 99.48 wt % Fe2O3 0.06 wt % Al2O3 0.21 wt % MgO < 0.01 wt % Such silica sand is commercially available from Rimer Silica, Texas, U.S.A. 10 A further relevant test for such applications and coatings is the so-called windshield wiper test, according to the TS1888 standard. The coated sample is mounted in a holder, and the outer coated surface is subjected, during 5 minutes, to 5000 wiper cycles per hour (2000 passes per hour) by a standard automotive windshield wiper lip with a wiper load of 20 grams per centimeter under addition of a mixture of sand and water (1 cm3 of sand according to DEF STAN 07-55 type 15 C in 10 milliliters of water). At the end of the test, the sample must not show any visible signs of scratching when visually inspected. In this test, a standard coating with a fluoride as the uppermost final layer was reduced in its layer thickness by an average of 70 nm (macroscopically viewed), while the reduction in 2020281146   10 Sep 2026 thickness of the coating according to the present disclosure was only 12 nm on average (macroscopically viewed). Both coatings exhibited the same spectral specification. To analyze these reduced layer thicknesses, reverse engineering of the optical layer design was carried out for the reflection spectra measured before and after the abrasion. 5 As a further standard test for verifying the abrasion resistance, the windshield wiper test according to the standard TS1888 was employed with dirty water. In this case, the windshield wiper exerts a pressure of 22 N and performs 100 movements per minute over an angular range of 60 degrees. The percentage alteration in haze is measured at appropriate intervals according 10 to the ASTM D1003 standard. Once the average haze value of the central field of view reaches 5%, this is generally considered as the end of the service life. Further options for verifying the abrasion resistance are a modified Bayer test that uses corundum sand, and sand and dust abrasion according to the MIL-STD-810G method 510.5. 15 The measurement of abrasion resistance is performed such that at least one of the following parameters is measured prior to and after carrying out at least one of the described test methods: - amount of surface defects according to ISO10110; - size of surface defects according to ISO10110; - light scattering, measured on the basis of the haze value; 20     - reflectance in a predefined range of wavelengths; - transmittance in a predefined range of wavelengths; or - distinctness of the image (DOI) transmitted through the component. FIG. 6 shows the increase in the haze value for the three optical components with layer systems 25 A, B, C after different application durations of the aforementioned test in compliance with MIL-STD-810G method 510.5. All three layer systems show very good resistance to scratching, and layer system B with the lowermost Al2O3 layer serving as an adhesion promoting layer exhibits the highest resistance. 30 When comparing an optical component embodying the present disclosure with a component having the same substrate material and a coating that is comparable with respect to its optical behavior, but in which the uppermost layer is made of a fluoride, a significant improvement in 2020281146   10 Sep 2026 abrasion resistance is resulting for a component embodying the present disclosure. Compared to an optical component that has an uppermost fluoride layer as mentioned above, it is apparent that, although the aforementioned parameters (amount and size of surface defects according to ISO10110, etc.) also deteriorate for an optical component embodying the present disclosure, this 5 deterioration is at least 20% less than in the case of the optical component with uppermost fluoride layer. Table: Relative properties of the optical components embodying the present disclosure with layer 10 systems A, B, C with respect to the so-called windshield wiper test, the dust and sand abrasion tests, and spectral performance: Test Layer system A Layer system B Layer system C Windshield wiper abrasion *** * ** Dust abrasion ** *** ** Sand abrasion (45 min) * * *** Spectral performance * ** *** very good good satisfying 15 It will be apparent to those skilled in the art that the invention is not limited to the exemplary embodiments, but may rather be varied within the scope of the subject matter of the claims. The features of the individual exemplary embodiments may in particular be combined with each other. 2020281146   10 Sep 2026 List of Reference Numerals 1     Substrate 2     Layer stack 5    3    Layer of second type 4     Layer of first type 5     Layer of third type 6    Adhesion promoting layer 7    Uppermost layer of 2 10    8    Second uppermost layer of 2 9    Lowermost layer of 2 10   Optical component 20    Layers of layer stack 2

Claims

1. An optical component, comprising a substrate that is partially transparent in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and from 7500 nm to 12,000 nm,5           provided with a layer stack comprising between five and thirty layers in total that defines ananti-reflection coating comprising at least three layers, the successive layers of the layer stack being made of at least three different materials or material combinations, wherein at least 50 % of the total thickness of the layer stack are oxide layers and / or at least half the number of layers of the layer stack are oxide layers,10           wherein the substrate with the layer stack exhibits a transmittance of at least 80 % at awavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and from 7500 nm to 12,000 nm, andwherein the layer stack includes an adhesion promoting layer directly on the substrate, which contains a material selected from the group consisting of aluminum oxide (Al2O3),15           magnesium oxide (MgO), yttrium oxide (Y2O3), DLC (diamond-like carbon), hafnium oxide(HfO2), and / or mixtures thereof.

2. The optical component of claim 1, wherein the substrate with the layer stack additionally exhibits transmittance of at least 80 % at a wavelength in at least one of the following20           spectral ranges:- in the visible spectral range;- in the near infrared range from 1000 nm to 1600 nm.

3. The optical component as claimed in any claim 1 or claim 2, wherein the layer stack25           includes at least one oxide layer of a first type and at least one oxide layer of a secondtype, wherein a layer of the first type has a higher refractive index than a layer of the second type, and wherein an uppermost layer and a second uppermost layer of the layer stack are provided, wherein the uppermost layer is an oxide layer of the second type or an oxide or fluoride layer of a third type, and the second uppermost layer is a layer of the first30           type.2020281146   10 Sep 20264. The optical component of claim 3, wherein the layer stack is formed as an alternating layer system comprising alternating layers including oxide layers of the first type and at least two oxide or fluoride layers of the third type, wherein the layers of the third type have a refractive index that is lower than the refractive index of the uppermost layer.

55. The optical component of claim 3, wherein the layer stack comprises an alternating layer system with layers of alternating refractive indices, wherein the uppermost layer of the layer stack forms part of the alternating layer system and has a lower refractive index than the second uppermost layer.

106. The optical component of claim 4 or claim 5, wherein the layer stack comprises a layer as the lowermost layer, which is made of a material different from the materials of the alternating layer system.15     7. The optical component as claimed in any one of claims 3 to 6, wherein the at least oneoxide layer of the first type comprises scandium oxide (Sc2O3) or hafnium oxide (HfO2).

8. The optical component as claimed in any one of claims 3 to 7, wherein the at least one oxide layer of the second type contains a material selected from the group consisting of20           hafnium oxide (HfO2), scandium oxide (Sc2O3), yttrium oxide (Y2O3), aluminum oxide(Al2O3), and / or mixtures thereof, preferably aluminum oxide.

9. The optical component as claimed in any one of claims 3 to 8, wherein the oxide or fluoride layers of the third type comprise aluminum oxide (Al2O3), yttrium oxide (Y2O3), yttrium25           fluoride (YF3), and / or mixtures thereof.

10. The optical component as claimed in any one of the preceding claims, wherein all layers of the layer stack are oxide layers.30     11. The optical component as claimed in any one of the preceding claims, wherein thesubstrate is made of an IR material, comprising a zinc chalcogenide, in particular zinc sulfide (ZnS) or zinc selenide (ZnSe), or a chalcogenide glass.2020281146   10 Sep 202612. The optical component as claimed in any one of claims 3 to 11, wherein the lowermost layer of the layer stack or as an adhesion promoting layer comprises yttrium oxide (Y2O3), or hafnium oxide (HfO2), or aluminum oxide (Al2O3), or magnesium oxide (MgO), wherein at least one further layer of the layer stack comprises scandium oxide (Sc2O3) or hafnium5           oxide (HfO2), and wherein the uppermost layer comprises aluminum oxide (Al2O3).

13. The optical component as claimed in any one of claims 3 to 12, wherein the adhesion promoting layer has the thinnest layer thickness of the layer stack and / or has a layer thickness ranging from 5 nm to 50 nm, preferably up to 30 nm.1014. The optical component as claimed in any one of claims 3 to 13, wherein the uppermost layer of the layer stack has a layer thickness in a range from 5 nm to 500 nm.

15. The optical component as claimed in any one of the preceding claims, wherein the optical 15           component shows no visible signs of scratches on the surface after a windshield wiper testin compliance with the TS1888 standard, and wherein preferably the amount of surface defects according to ISO10110 is reduced by at least 20 % in comparison to an optical component with a fluoride layer as the uppermost layer, and / or exhibits a haze of less than 30 % after a "sand & dust" test in compliance with MIL-STD-810G method 510.5.2016. A method for producing an optical component with an anti-reflection coating as claimed in any one of the preceding claims, comprising applying, on a substrate, a layer stack comprising between five and thirty layers in total and consisting of a plurality of successive layers of different materials to forms an anti-reflection coating, wherein the layers of the25           layer stack are successively deposited of at least three different materials or materialcombinations, wherein at least 50 % of the total thickness of the layer stack are oxide layers and / or at least half the number of layers of the layer stack are oxide layers, and wherein the substrate with the layer stack exhibits a transmittance of at least 80 % at a wavelength in at least one of the infrared spectral ranges from 3500 nm to 5000 nm and30          from 7500 nm to 12,000 nm.2020281146   10 Sep 202617. The method as claimed in claim 16, wherein an adhesion promoting layer is deposited directly on the substrate, which contains a material selected from the group consisting of aluminum oxide (Al2O3), magnesium oxide (MgO), yttrium oxide (Y2O3), DLC (diamond-like carbon), hafnium oxide (HfO2), and mixtures thereof.

518. The method as claimed in claim 16 or claim 17, wherein the layer stack includes at least one oxide layer of a first type and at least one oxide layer of a second type, wherein a layer of the first type has a higher refractive index than a layer of the second type, and wherein a second uppermost layer and an uppermost layer are deposited, wherein the second10           uppermost layer is a layer of the first type and the uppermost layer is a layer of the secondtype or an oxide or fluoride layer of a third type.

19. The method as claimed in any one of claims 16 to 18, wherein the uppermost layer of the layer stack is applied by a technique selected from the following: ion plating, ion15           implantation, ion beam-assisted or plasma-assisted deposition, magnetron sputtering, ionbeam sputtering, cathodic arc deposition, and atomic layer deposition.

20. The method as claimed in any one of claims 16 to 19, wherein prior to the deposition of the layer stack, the surface of the substrate is modified by at least one process selected from 20           ion implantation, etching, leaching, or wet-chemical ion exchange.

21. The method of claim 20, wherein a chalcogenide substrate, in particular a sulfide or a selenide, or a chalcogenide glass is used as the substrate, and wherein the surface thereof is modified by alkaline etching.2522. Use of the optical component as claimed in any one of claims 1 to 15 as a cover glass and protective glass for optical and optronic components, such as cameras, rangefinders and periscopes, in particular in aircraft, aerial vehicles, track vehicles, wheeled vehicles, motor vehicles, unmanned aerial vehicles such as missiles or rockets or drones.

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