DE102006035688A1 - Substrate for decoratively colored coating on door latches, jewelry or clocks, comprises a coating, which has layers of different materials including a covering layer, transparent spacer layer, and a semitransparent metal layer - Google Patents

Abstract

The substrate (2) for decoratively colored coating on door latches, jewelry or clocks, comprises a coating, which has layers of different materials including a covering layer (12), which is formed as a transparent or semitransparent protective layer and as a transparent or semitransparent intermediate layer formed between the covering layer and the substrate, a transparent spacer layer (8) arranged between the covering layer and the substrate or a metallic mirror layer (6), and a semitransparent metal layer (10) arranged between the spacer layer and the covering layer. The substrate (2) for decoratively colored coating on door latches, jewelry or clocks, comprises a coating, which has layers of different materials including a covering layer (12), which is formed as a transparent or semitransparent protective layer and as a transparent or semitransparent intermediate layer formed between the covering layer and the substrate, a transparent spacer layer (8) arranged between the covering layer and the substrate or a metallic mirror layer (6), and a semitransparent metal layer (10) arranged between the spacer layer and the covering layer. The substrate coating-side has a metallic surface or the substrate is coated with the metallic mirror layer, which has a minimum thickness of 50 nm. The spacer layer has a transmission of 70% or more for the region of the visible light, and thickness of 30-1000 nm. The semitransparent metal layer is homogeneous and uniform and has a thickness of 1-20 nm. The covering layer has a transmission of 50% or higher for the region of the visible light, and a thickness of 30-4000 nm. The coating has a selective maximum reflection of 50% or more in the region of the visible optical spectrum of 380-780 nm. The maximum of the reflection focal point of an electro magnetic radiation in the visible area shifts itself in an area wise reduction of the thickness of the covering layer after applying on the substrate of less than 30 nm in the wavelength dependent reflection spectrum. The substrate has a cylindrical surface form in the coating area. The transparent spacer layer has high-refraction and the transparent covering layer has low-refraction. An independent claim is included for a procedure for coating a substrate.

Description

The The invention relates to a substrate with a coating comprising a Sequence of several layers of different material including a cover layer having. The invention further relates to a method for Coating a substrate.

at The substrate is a solid or a base material with a surface. The substrate may be made of different material, such as metal, Plastic, glass, ceramics, and the like. The substrate can be in the shape of a solid molding available. The substrate serves as a support for a coating applied thereto Coating.

Out the prior art are in particular coatings of substrates known to serve the decor purposes. In the decorative area, for example colored coatings on doorknobs, Applied jewelry or watches. With the colors applied However, these are their own colors, that is, that the layer material from a minimum thickness of about 50 nm always the same color shows. As coatings are here, for example TiNx with yellow to golden yellow, CrNx with silver to gray, TixAl1-x Ny with copper. Bronze anthracite or gray-blue, TiCx with gray, TiCxNy with golden, yellow, violet, gray-blue or silver blue, diamond with light gray and DLC with dark blue color known.

There are no special requirements for homogeneity here. The available colors are very limited and their selective reflectivity or brilliance is in comparison to interference effects based layer systems, as for example in the Scriptures DE 100 11 597 A1 be described, very weak.

From the decorative field, it is known to use colored interference layer systems, for example, applied to films in order to achieve interesting color effects. Examples of such layer systems can be found in the publications EP 1 490 214 B1 . DE 40 17 220 A1 . WO 2005/085780 A1 or CA 2 235 948 A1 , Layer systems which also show layer thickness-dependent color effects, but which are based on the effect of surface-enhanced absorption, are used, for example, in the field of counterfeit protection for banknotes or packaging. In the field of architecture or, for example, in car glazing, functional layers are applied which are used as low-E, heat protection layers, or the like. Filter layers. These all have a high degree of transparency ( US 4,964,963 ; US 902,581 ). Optical coating systems are also used in the field of counterfeit protection.

Here they are used, for example, to mark banknotes or outer packaging and thus to make them recognizable as originals ( EP 0 733 919 B1 . AT 4 133 360 B . EP 1 558 449 A1 EP 1 377 461 B1 . US Pat. No. 2005 20051 038 A1 ).

With Although interference effects can be a variety of high-intensity Create colors and color effects, but these are extremely different from the layer thicknesses dependent on the materials involved. So show, for example, a few percentage points of different layer thicknesses strong different colors. Because coatings of substrates easily can be removed or scratched, these are known Interference layer systems are not suitable as decorative coatings, because they look unsightly very quickly. Scratches in the surface and due to wear thinner shifts have become due to the difference in color that then occurs immediately recognizable and stand out.

A variety of known functional layers or layer systems on substrates is produced in thin-film technology by means of physical vapor deposition (PVD) or chemical vapor deposition (CVD). Thus, workpieces such as drills, cutters or cutting tools are coated so that their surfaces is more resistant to wear. According to EP 0 725 428 A3 Thin films are used as diffusion barrier layers. Also known are thin layers with special electrical properties (eg, indium tin oxide "ITO"), which are used in touch panels, among others. There are known thermal barrier coatings (thermal barrier coatings), which are provided for example in the coating of turbine blades.

It especially in the field of decorative layers there is a desire To provide colored coatings, which are characterized by particularly brilliant Distinguish colors while maintaining a high resistance to mechanical Wear. Also, should change the surface layer thickness - for example through wear or Scratch - the If possible, color impression exist stay.

Accordingly, it is the object of the present invention, a coating on a Substrate and a method for its production, the with little technical effort largely arbitrary color structures allows and thereby a long-term stable protection of this decorative cover layer guaranteed is.

The invention solves this problem for a generic substrate by the cover layer as a transparent or semitransparent protective layer and between the cover layer and the substrate at least one transparent or semitranspa rente intermediate layer is formed. The object is achieved for a generic method by applying to the substrate at least one transparent or semitransparent intermediate layer and one transparent or semi-transparent covering layer within a coating process.

at the coating of a substrate according to the teaching of the invention result from the coating a variety of brilliant colors and color effects, which are very resistant to wear due to the cover layer. Due to the top layer the color impression remains even with a wear-related Material removal or scratches received.

The Number of colors and color effects can be increased in particular if as coating a layer sequence is used, in which a metallic Game gel layer, which also consists of a metallic substrate itself may consist of a transparent spacer layer and a transparent cover layer is applied. A special protective effect can be the top layer unfold when formed as a ceramic hard material layer is. Between the transparent spacer layer and the cover layer can be an extra semitransparent thin Metal layer may be arranged. With such a layer sequence arise for Decorative purposes well usable interference effects.

With the structure of the invention the cover layer is used for a variety of application areas proposed a structure with which the demands on the functionality can be fulfilled and at the same time for decorative Purpose individual and brilliant colors or color effects achievable are. This multilayer inventive System met at the same time respective functionality and color requirements, wherein on the substantially arbitrary substrate or its surface, the multilayer covering layer with a homogeneity can be applied, the deviations of less than 2%.

The Substrate may consist of a flat material with flat surfaces, such as glass, ceramics, especially tiles, metal or plastic. But it is also possible to make the substrate rotationally symmetric, in particular cylindrical. In these mold designs is a uniform material order for the production the individual layers well possible. While a coating pass of a substrate through a coating system can successively applied several layers on a substrate become. The substrate can be as a belt or on a conveyor belt go through the respective processing stations, or it rotates along different processing stations. The multi-layered Cover layer-producing coating process can in one single coating pass, for example in the form of a sputtering process, carried out become.

Especially are by PVD (Physical Vapor Deposition) on the selected substrate Layer systems to produce, on the one hand brilliant colors or Show kippfarben effects and at the same time have a functionality, i.e. e.g. wear-, are temperature or chemical resistant. Also can electrical properties and / or (diffusion) barrier properties integrated into the system or the respective layers of the cover layer become. Between the substrate and the respective layers of the functional Color layer structure, an adhesion improvement can be applied, wherein a chromium or Titanlage with a thickness D = 2 to 10 nm provided can be.

• – Substrat: Metall, Glas, Kunststoffe, Keramiken (Fliesen), Holz, Stein,
• – metallische Spiegelschicht: Al, Ag, Au, Cu, Cr, Fe, Ti, Stahl, TiAlx oder Legierungen,
• – transparente-Abstandsschicht: Oxide, Nitride, Oxinitride, Oxicarbide, Carbonitride oder DLC (Schichtdicken zwischen 40 und 600 nm), und
• – Semitransparente Metallschicht: Al, Ag, Au, Cu, Cr, Fe, Ti, Stahl, TiAlx oder Legierungen.

Intended material combinations:

• - Substrate: metal, glass, plastics, ceramics (tiles), wood, stone,
• Metallic mirror layer: Al, Ag, Au, Cu, Cr, Fe, Ti, steel, TiAlx or alloys,
• Transparent spacer layer: oxides, nitrides, oxynitrides, oxicarbides, carbonitrides or DLC (layer thicknesses between 40 and 600 nm), and
• Semitransparent metal layer: Al, Ag, Au, Cu, Cr, Fe, Ti, steel, TiAlx or alloys.

The Colors are due to an interference effect (similar to: Fabry-Perot effect). The light passes through the transparent Cover layer on the semi-transparent metal layer, in part reflected and partly it passes through this layer as well as through the subsequent transparent layer and finally on the non-transparent, reflective metal layer reflects. From here, the light comes back to the semitransparent Metal layer, where it reflects again in part and partly transmitted becomes. This leads to, that under different emission angles each specific wavelengths constructive interfere and so angle dependent corresponding colors arise. The color itself is essentially through the thickness of the spacer layer and the cover layer set. The Semitransparent metal layer essentially determines the intensity of the color.

It is advantageous that, by suitable choice of the cover layer material, either the protective layer thickness imperceptibly influences the resulting color for the eye, ie in this case the coated substrate is long-term stable; it also retains its color when the protective layer thickness is reduced due to wear - or a transparent layer is selected which selectively targets the color as the layer thickness is reduced due to wear of the thus coated substrate changed. This sensor effect is interesting in the coating of drills; For example, a new drill will turn red and after frequent use it will turn blue - a signal for the user to change the drill because the coating has become unusable.

One Another example is the coating of turbine blades Aircraft engines with thermal barrier coatings; here can be at a suitable location within the commonly used yttrium-stabilized Zirconium oxide layer integrate a semi-transparent metal layer, which then causes a distinct color effect throughout the system, without significantly degrading the barrier properties. With increasing number of start / landing cycles exploits the layer surface and the color changes yourself. It would not have to be that way more like before after a standard number of cycles the whole Turbinenschaufein be replaced (because this their state not yet seen), but on the basis of a color chart, is one Fast optical control of every single blade possible.

Advantageous is that within a coating process, the functionality (mechanical, thermal, electrical or chemical property improvement) of coatings combined with brilliant color properties.

Advantageous is that the Color generation is based on a physical interference effect (i.e., not dependent on the material properties themselves) and therefore the specific properties required by customers can be ensured by the choice of suitable materials.

Advantageous is that means PVD also under normal conditions not thermochemically stable phases, so-called metastable phases can be generated, such as oxynitrides or oxicarbides which are "tailored" to a required functionality.

Advantageous is that this Coatings can be applied structured, i. that e.g. just Logos, brand names or logos - or these surrounding surfaces - in these functional color layers can be applied. This is achieved by that means a laser the desired Structures are "evaporated" after coating.

alternative a lift-off procedure is used; in this case, before the coating a vacuum-resistant and heat-resistant Ink on the desired Places applied - preferred with the pad printing process or the screen printing process. Then the samples are coated and then the coated ink removed by a wash. This ensures that only the non-printed surfaces be provided with the functional ink layer system.

Advantageous is that at suitable choice of the laser wavelength, -energy and intensity the covering layer can be removed in a targeted manner so as different Color effects between logos, brand names. Lettering and surrounding surface to achieve.

Advantageous is that through partially covering the sample surface during coating different Colors or color effects during a coating run can be achieved.

Advantageous is that beside the coating of the surface from plan substrates also the homogeneous coating of cylindrical Samples with the same diameters, such as drills, cutters, sleeves of Writing instruments Tubes, or even in particular about an axis rotationally symmetrical bodies like bars for manhole covers, Indexable inserts and the like, on the outer sides is possible.

Advantageous is that no Metal clusters are used in the semitransparent metal layer, but only thin Metal layers that retain their metallic properties. That the effect of surface-enhanced absorption (Surface Enhanced Absorption) is not used, as this is plant technology aufwen dig is to be realized and therefore negative in terms of cost would make noticeable.

Advantageous is that the Underside of the semitransparent metal layer is such That you have the partially reflected by the mirror layer reflected radiation and partially reflected, so that the resulting colors on the angle-dependent constructive interference of electromagnetic radiation.

Further advantageous embodiments result from the features of Subclaims, the Drawings and the following objective description.

The Invention will now be explained in more detail with reference to embodiments. Show it:

1 a substrate having a first coating,

2 a substrate with a second coating,

3a : a structure of a sputtering plant in a supervision,

3b : a side view of in 3a shown sputtering machine,

4 : a reflection spectrum of in 1 layer sequence below 0 °,

5 : this in 4 shown reflection spectrum and a spectrum of an identical layer sequence in which the cover layer has a different thickness.

In 1 is on a substrate 2 a first coating 4 shown schematically with an exemplary layer sequence. On the substrate 2 is a covering, metallic mirror layer 6 applied, which may for example consist of chromium with a layer thickness of 100 nm. On top of that is a transparent spacer layer 8th applied, which may for example consist of a 290 nm thick SiO ₂ layer. This is followed by a semitransparent metal layer 10 For example, from 4 nm thick chrome. Finally, a transparent SiO ₂ layer, for example 1000 nm thick, is used as cover layer 12 applied.

The covering metallic mirror layer 6 , the transparent spacer layer 8th and semi-transparent metal layer 10 Together they form an intermediate layer between the substrate 2 and the topcoat 12 is arranged. In this case, the individual layers of the intermediate layer are configured differently transparent already in the exemplary embodiment. The number of intermediate layers and their design, in particular the material used and its thickness and the associated respective transparency, are dependent on the desired colors and color effects.

If the substrate 2 itself has a metallic surface, can on a separately applied metallic mirror layer 6 be omitted, since the metallic surface has optical properties that are comparable to a metallic mirror layer. Is a metallic mirror layer 6 If present, this may consist of one of the metals Au, Ag, Cu, Cr, Ti, Al, In, Sn, Zn, Pd or TiAlx. The metallic mirror layer 6 should have a minimum layer thickness of 50 nm.

The transparent spacer layer 8th is between the topcoat 12 and the substrate 2 or the metallic mirror layer 6 arranged. The spacer layer should have a transmission of more than 70% for the visible light range. The spacer layer should have a layer thickness between 30 nm and 1000 nm. A layer thickness between 50 nm and 600 nm is preferred, and a layer thickness between 70 nm and 400 nm is preferred. The spacer layer may comprise at least one of metal oxide, metal nitride, metal oxynitride, metal carbide, tin oxide, tin oxynitride, zinc oxide, zinc oxynitride, aluminum nitride, Alumina, aluminum oxynitride, silica, silicon oxynitride, titanium oxide, titanium oxynitride, niobium pentoxide or indium-tin oxide.

It is advantageous if the semitransparent metal layer 10 is homogeneous and even and has a layer thickness of 1 nm to 20 nm. A layer thickness between 4 nm and 15 nm is preferred, and a layer thickness of 7 to 12 nm is particularly preferred. The semitransparent metal layer 10 may consist of at least one of the metals Au, Ag, Cu, Cr, Ti, Al, In, Sn, Zn, Pd or TiAlx.

The cover layer 12 is designed transparent in the embodiment, but it can also be designed semitransparent. The cover layer 12 should have a transmission of at least 50% or higher for the visible light range. For the cover layer, a layer thickness between 30 nm and 4,000 nm is proposed. According to a preferred embodiment, the layer thickness is between 100 nm and 2000 nm, and according to a particularly preferred embodiment, the layer thickness entered between 200 nm and 2000 nm. The cover layer 12 may consist of one of the materials alumina, aluminum oxynitride, silicon nitride or silicon oxynitride.

Overall, it is suggested that the coating 4 in a range of the visible optical spectrum from 380 nm to 780 nm has a selective maximum reflection of at least 50% or more in order to obtain a satisfactory color yield and color effects from the coating 4 to achieve.

The maximum of the reflection centroid of an electromagnetic radiation in the visible range should be in a region-wise reduction of the thickness of the cover layer 12 after application to the substrate 2 For example, due to wear or scratches, move 30 nm or less in the wavelength-dependent reflection spectrum to avoid unwanted color effects and impressions. Almost homogeneous colors result when the angle-dependent color effect that occurs in interference-based color layers is reduced by the choice of materials and layer thicknesses such that when the viewing angle changes by 40 °, the wavelength position of the reflection maximum is less than 12 nm, preferably less than 8 nm, and more preferably shifts less than 5 nm.

According to a further embodiment of the invention, the coating 4 temperature resistant. By a suitable selection of the materials used and layer thicknesses, the coating 4 be designed so that the color impression does not change, that is, the reflection spectrum is shifted by less than 5 nm when the substrate 2 with the coating 4 to 400 ° C, preferably to 500 ° C, more preferably to 600 ° C, is heated. When choosing materials that do not oxidize and that are resistant to diffusion, even a temperature resistance of up to 800 ° C can be achieved.

According to one embodiment, it is provided that the layer sequence is selected such that when the substrate thus coated is touched 2 with the hand or the finger the remaining human fingerprint hardly or not at all is recognizable. By selecting suitable materials and layer thicknesses, the reflected portion located in the visible range can be reduced by more than 30%, preferably by more than 40%, and particularly preferably by more than 50%, by a fingerprint located on the surface of the layer sequence. The fingerprint fat layer is thus used in the design of the coating 4 considered as an additional optical layer that is integrated into the overall layer construction.

The coating 4 can on flat surfaces, but also rotationally symmetric, preferably cylindrical surfaces of a substrate 2 be applied. The application can also be done on a metal band.

According to one embodiment of the invention, it is provided that the angle-dependent color effect which naturally occurs in interference-based color layers is reduced so that the resulting color appears homogeneous to the human eye, ie does not subjectively change when viewed at different angles. This is achieved by using as a spacer layer 8th a material having a higher than average refractive index, in comparison with the theoretically usable materials, such as titanium oxide or niobium pentoxide. The other materials and layer thicknesses must be adapted accordingly, for example, by the transparent cover layer 12 below average breaking is designed.

In 2 is an embodiment with a substrate 2 with a coating 4 shown in which the semitransparent protective layer 10 is missing. The spacer layer 8th and the topcoat 12 are designed by the material and the layer thickness so that the desired optical effects even without the semitransparent protective layer 10 be achieved. Notwithstanding the in the 1 and 2 illustrated embodiments, additional layers of material may be present, or the layer thicknesses may be varied in a suitably distinguished manner.

The coating 4 with the intermediate layers 6 . 8th . 10 and the topcoat 12 , which can be transparent or semi-transparent at will, can be magnetron sputtered onto the substrate 2 be applied in a workflow as a coating process. In this case, successively in a device on a substrate 2 applied the respective layers. The respective layers are applied in such a way that they are applied to the substrate 2 applied total layer thickness varies less than 2% over the coated area.

In 3a is an example of the structure of a suitable magnetron sputtering device sketched from a perspective from above. These are the flat substrates to be coated 2 outside on the lateral surface of a drum-shaped charging device or a Chargierkorbes 14 applied. On both sides of the recipient are the opposite cathodes 18 , The targets used here are, for example, chromium and SiO ₂ . After evacuation of the recipient 16 and plasma cleaning of the samples is first a metallic, opaque mirror layer 6 from, for example, 100 nm chromium is applied in such a way that the chromium target is atomized in the argon plasma. In order to achieve a homogeneous coating, the charging basket is used throughout the coating 14 evenly rotated. The second target is used for the second layer: a plasma consisting of oxygen and argon is ignited in order to homogeneously deposit 290 nm SiO ₂ . Then we apply a homogeneous, even semi-transparent 4 nm thick Cr layer as a chromium target under pure argon plasma. In the last coating step, a transparent wear protection layer, for example SiO _2, having a thickness of 1000 nm is applied under an argon / oxygen plasma. In 3b there is a side view of in 3a shown device.

In 4 is that in the 1 described coating 4 corresponding reflection spectrum is shown below 0 °, where the x-axis reflects the reflection in percent and the y-axis the wavelength in nm.

In 5 is that in the 1 corresponding reflectance spectrum below 0 ° and two further spectra below 0 °, which result from a correspondingly altered layer structure, in which the only difference is the SiO ₂ protective layer thickness 2,000 nm or 500 nm. It can be seen that the optical color impression of the heavy corresponds to the point of maximum reflection, is maintained.

The above objective Description is for explanatory purposes only and is not directed to the subject matter of the invention on the embodiments to restrict. It is not difficult for a person skilled in the art, the doctrine disclosed in a manner that seems suitable to a use case as far as it is useful appears.

Claims (22)

Substrate ( 2 ) with a coating ( 4 ) comprising a sequence of several layers of different material including a cover layer ( 12 ), characterized in that the cover layer ( 12 ) as a transparent or semi-transparent protective layer and between the top layer ( 12 ) and the substrate ( 2 ) at least one transparent or semitransparent intermediate layer ( 6 . 8th . 10 ) is trained. Substrate ( 2 ) according to claim 1, characterized in that the substrate ( 2 ) has a metallic surface on the coating side or the substrate ( 2 ) with a metallic mirror layer ( 6 ) is coated. Substrate ( 2 ) according to claim 2, characterized in that the metallic mirror layer ( 6 ) at least one of the metals Au, Ag, Cu, Cr, Ti, Al, In, Sn, Zn, Pd or TiAlx consists. Substrate ( 2 ) according to one of the preceding claims 2 or 3, characterized in that the metallic mirror layer ( 6 ) has a minimum layer thickness of 50 nm. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that between the cover layer ( 12 ) and the substrate ( 2 ) or the metallic mirror layer ( 6 ) a transparent spacer layer ( 8th ) is arranged. Substrate ( 2 ) according to claim 5, characterized in that the spacer layer ( 8th ) has a transmission of more than 70% for the visible light range. Substrate ( 2 ) according to one of the preceding claims 5 or 6, characterized in that the spacer layer ( 8th ) has a layer thickness between 30 nm and 1000 nm. Substrate ( 2 ) according to one or more of the preceding claims 5 to 7, characterized in that the spacer layer ( 8th ) of at least one of metal oxide, metal nitride, metal oxynitride, metal carbide, tin oxide, tin oxynitride, zinc oxide, zinc oxynitride, aluminum nitride, aluminum oxide, aluminum oxynitride, silicon oxide, silicon oxynitride, titanium oxide, titanium oxynitride, niobium pentoxide or indium-tin oxide. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that between the spacer layer ( 8th ) and the cover layer ( 12 ) a semi-transparent metal layer ( 10 ) is arranged. Substrate ( 2 ) according to claim 9, characterized in that the semitransparent metal layer ( 10 ) is homogeneous and even and has a layer thickness of 1 nm to 20 nm. Substrate ( 2 ) according to one of the preceding claims 9 or 12, characterized in that the semitransparent metal layer ( 10 ) consists of at least one of the metals Au, Ag, Cu, Cr, Ti, Al, In, Sn, Zn, Pd or TiAlx. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the cover layer ( 12 ) has a transmission of at least 50% or higher for the visible light range. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the cover layer ( 12 ) has a layer thickness between 30 nm and 4,000 nm. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the cover layer ( 12 ) consists of at least one of the materials alumina, aluminum oxynitride, silicon oxide or silicon oxynitride. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the coating ( 4 ) has a selective maximum reflection of at least 50% or more in a range of the visible optical spectrum of 380 to 780 nm. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the maximum of the reflection centroid of an electromagnetic radiation in the visible region with a reduction in the thickness of the covering layer ( 12 ) after application to the substrate ( 2 ) shifts by less than 30 nm in the wavelength-dependent reflection spectrum. Substrate ( 2 ) according to one or more of the preceding claims, characterized net that the substrate ( 2 ) at least partially made of glass, ceramic, metal, wood and / or plastic. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the substrate ( 2 ) has a plane or rotationally symmetrical, preferably cylindrical surface shape in the coating area. Substrate ( 2 ) according to one or more of the preceding claims, characterized in that the transparent spacer layer ( 8th ) high refractive index and the transparent cover layer ( 12 ) are configured low breaking. Process for coating a substrate ( 2 ), characterized in that at least one transparent or semitransparent intermediate layer ( 6 . 8th . 10 ) and a transparent or semitransparent cover layer ( 12 ) on the substrate ( 2 ) are applied within a coating process. A method according to claim 20, characterized in that at least one layer of the coating ( 4 ) are applied by means of magnetron sputtering. A method according to claim 20 or 21, characterized in that the entire layer sequence is applied so that the on the substrate ( 2 ) applied total layer thickness varies less than 2% over the coated area.