DE102014108651B4 - Infrared radiation reflecting layer system with high stability against mechanical stress and method for its production - Google Patents

Abstract

Infrared radiation reflecting layer system on a transparent, dielectric substrate (S) with the following transparent layer arrangements, viewed from the substrate (S) upwards: - a base layer arrangement (GA) with at least one dielectric base layer (GAG) of a nitride, oxide or oxynitride of a metal, a Semiconductor or a semiconductor alloy, - a functional layer arrangement (FA) with a zinc oxide-containing seed layer (FAK) and an overlying silver-based functional layer (FAF), - wherein the functional layer (FAF) of several sub-layers (FAFT1, FAFT2, ...) with different mean Oxidation number of the silver or is constructed as a gradient layer with grading mean oxidation number of silver, starting from a non-oxidized silver layer, the average oxidation number increases towards substrate, - a cover layer arrangement (DA) with at least one dielectric cover layer (DAD) of a nitrile d, oxide or oxynitride of a metal, a semiconductor or a semiconductor alloy.

Description

The invention generally relates to an infrared radiation (IR radiation) reflecting layer system on a transparent, dielectric substrate and to a method for producing such a layer system.

Functionally, an IR radiation-reflecting layer system, hereinafter also referred to only as a layer system, characterized by its low emissivity and the associated high reflectivity and low transmission in the spectral IR range (wavelengths of >> 3 microns). At the same time a high (low-E layer systems) or targeted reduced transmission (low-E-Sun layer systems) in the visible light range should be achieved. The layer system thus has a steep drop in transmission and a large increase in reflection in the transition from visible light to near infrared. Due to their emission behavior, such layer systems are generally referred to as low-E layer systems.

A layer system has transparent, functionally distinguishable layer arrangements in order to achieve the described properties.

The term "layer arrangement" as a rule comprises more than one layer, but also includes that a layer arrangement consists only of a single layer, which realizes the respective function. Such a layer arrangement can comprise both homogeneous individual layers and those with gradual variations of the composition over the layer thickness, so-called gradient layers. The assignment of individual layers to the layer arrangements is not always unambiguous, since each layer has an influence on the adjacent layers as well as on the entire system. The assignment of a layer to a specific layer arrangement is based on their function.

In general, a layer system, viewed from the substrate upwards, initially comprises a base layer arrangement which serves primarily as a mediator between the substrate and the further layer sequence, in particular the adhesion of the system to the substrate. The layers of the base layer arrangement can also influence the properties of the layer system as a whole, such. As the chemical and / or mechanical resistance, as well as the adjustment of optical properties and the anti-reflection serve.

Overlying the base layer arrangement is a functional layer arrangement which comprises at least one, usually metallic, functional layer as the IR reflection layer and optionally further layers, for example metallic ( EP 1463689 B1 ) or dielectric ( EP 1851354 B1 ) Blocker layers. The complementary layers support the function of the IR reflection layer and allow influencing the optical and associated electrical properties as well as the chemical and mechanical properties of the functional layer and / or serve to improve the adhesion. It is thus known, in particular, that the surface resistance of the functional layer deposited there above is reduced by means of a seed layer and its IR reflection can thus be positively influenced by the seed layer having a positive influence on the growth of the functional layer.

The high reflection in the IR range is generally achieved for the said layer systems by one or more, usually metallic, functional layers. As a rule, the edge described above in the spectral transmission and reflection behavior becomes steeper with increasing number of the IR-reflecting functional layers, that is to say the selectivity increases, which is why layer systems with two or more functional layers are increasingly being used. However, this places increased demands on the production and processing conditions as well as on downstream process steps in the further processing of the coated substrates.

Pure silver or silver alloys are typically used as the material for the functional layer to produce low-emissivity layer systems for architectural glass applications. This material has high reflectivity even at low layer thicknesses, especially in the infrared range, combined with low absorption in the visible spectral range of the light. A simple low-E layer system usually contains an approximately 10-15 nm thick silver layer. In addition, silver oxide layers for reflection and absorption of UV radiation, for example from the US 2002/0068167 A1 known.

In the course of deposition, use and in various applications, including during the subsequent processing of the deposited layer system occurs, often due to the associated temperature stresses, to various, the reflectivity of the functional layer and the transmission of the layer system changing processes, in particular for the diffusion of components Layers of the base or cover layer arrangement in the functional layer and vice versa. As a result, oxidation processes can adversely affect the function of the functional layer.

To avoid such diffusion and oxidation processes may adjacent to Functional layer one or both sides blocking layers are inserted, which serves as a buffer for the diffusing components. These blocker layers are structured and arranged according to the expected temperature load and protect the sensitive, often very thin functional layer against the influence of adjacent layers. By inserting the blocking layers, it is possible, in particular, to prevent the oxidation of the functional layer and the associated increase in sheet resistance or even pronounced color shifts of the layer system during the coating processes themselves or as a result of an annealing process.

As blocking layers z. B. nickel and / or chromium containing layers which include the IR-reflecting silver layers ( DE 035 43 178 A1 . EP 0 999 192 B1 . US 2004/0180214 A1 and EP 1 174 397 A2 ) or at least protect it on one side.

In addition, it has been found that the reflection and transmission properties of the layer system are also influenced by diffusion processes originating from the substrate. In order to influence this, in particular for temperable layer systems, when using glass as a substrate material below the functional layer arrangement, regularly in the base layer arrangement, a barrier layer is inserted, which the diffusion of constituents of the glass, such as. B. alkali metal ions in the layer system to reduce. Also, with such a barrier layer, quality problems due to undefined initial conditions in the raw glass, that is, a fluctuating chemical composition of the glass, or other glass influences can be reduced.

In addition, other glass influences, such as corrosion or prints of the glass handling nipples, which are often undetectable by visual inspection and can not be eliminated by conventional cleaning, cause undesirable changes in the properties of the layer system. Particularly disadvantageous in such glass influences that their effects on the properties of the layer system will be visible only later.

Layers of the cover layer arrangement close off the layer system and, like the base layer arrangement, can functionally affect the entire system. A cover layer arrangement comprises at least one mechanically and / or chemically stabilizing protective layer. This can influence itself or through complementary layers and the optical properties of the layer system, for. B. by an anti-reflective coating.

The cover layer arrangement usually consists of one or more layers of a dielectric oxide, nitride or oxynitride of a metal, a semiconductor or a semiconductor alloy, usually with a high refractive index, with more than one layer also with changing refractive index. The latter is known as a high-low cover layer arrangement.

A protective layer closing off the IR-reflecting layer system serves to protect the layer system from mechanically or chemically induced changes. For this reason, the choice of material of the anti-reflective layers of the cover layer arrangement is made so that a material with higher mechanical and / or chemical strength is used as the final protective layer. However, the choice of material is dependent on the layers of the cover layer arrangement and in particular on the directly adjacent layer due to the desired anti-reflection effect.

A layer system constructed as described, which comprises only one functional layer arrangement, can be supplemented by insertion of one or more further functional layer arrangements (double, triple, or multi-low E), which are arranged by way of coupling or interlayer arrangements over the first functional layer arrangement ( DE 10 2011 087 967 A1 ). The interlayer arrangements serve in particular for antireflection coating in the visible range by functional separation of the two functional layer arrangements from one another and their connection to one another. In addition, with a suitable combination of materials by an interlayer arrangement and a mechanical stabilization of the layer system can be achieved.

The deposition of the various layer systems often takes place by means of sputtering, which enables the production of suitable individual layers with only very small layer thicknesses with the required homogeneity, their composition and properties are set very well and reproducibly by means of the target materials, the type of sputtering and the sputtering parameters can.

It has been shown that the various types of low-E layer systems described are still mechanically sensitive and correspondingly difficult to process, despite the diverse design possibilities. In particular, if the required processing conditions for the individual subsequent process steps, such. As cutting, grinding (Grinden) or washing, for example, with alcoholic cleaning agents, due to older and insufficiently suitable systems are not or not fully feasible, comes it often leads to layer destruction and correspondingly high reject rates. Thus, the coating can be scratched and / or partially peeled off quickly under poor processing conditions. Furthermore, such a coating can also increasingly take damage during transport between manufacturer and processor.

Object of the present invention is therefore to provide a low-emission layer system with high stability to mechanical stresses without appreciable influence on the optical properties of the layer system and a method for its preparation.

In particular, the layer system should be less susceptible to scratches and with ethanol not wipeable.

This object is achieved by a layer system with the features of claim 1 and a method according to claim 5. The respective subclaims give embodiments of these inventive solutions again.

Surprisingly, it has been found that in terms of mechanical stability, the adhesion between metals and oxides is classified as particularly critical. This particularly concerns the adhesion of the functional layer to the underlying seed layer. Depending on the materials in the base layer arrangement arranged below the seed layer and the deposition processes, the interface between the seed layer and the functional layer has a different roughness, which influences the adhesion.

The layers of the cover layer arrangement arranged above the functional layer and any blocker layer also act on the underlying interfaces depending on the materials and deposition conditions due to different layer stresses, usually compressive stresses.

In the case of non-optimal conditions, in particular, the interface between germ and functional layer fails, so that sufficient adhesion no longer exists. This is often expressed by the fact that the layers above the seed layer can easily be rubbed away with an ethanol-soaked cloth.

To improve the mechanical stability, the layer system according to the invention therefore has an improved adhesion between germ and functional layer.

The layer system according to the invention comprises a base layer arrangement with at least one dielectric base layer made of a nitride, oxide or oxynitride of a metal, semiconductor or a semiconductor alloy.

Above the base layer arrangement, the layer system according to the invention has a functional layer arrangement which comprises a zinc oxide-containing seed layer and a silver-based functional layer arranged above it. The functional layer is either made of several partial layers with different oxidation number of the silver or as a gradient layer with gradierender, d. H. built up continuously changing, oxidation number of the silver, wherein the oxidation number increases from a non-oxidized silver layer in the direction of substrate.

On the side opposite to the substrate, the layer system according to the invention is terminated by a cover layer arrangement having at least one dielectric cover layer made of a nitride, oxide or oxynitride of a metal, a semiconductor or a semiconductor alloy.

In addition to the layers mentioned, the layer system according to the invention can comprise further layers at all positions within the layer system, unless a direct arrangement of two specific layers on each other is expressly provided. These additional layers can serve for example to improve the optical and mechanical properties or to generate a specific color impression. In particular, a blocking layer can be inserted above the functional layer.

"Off" in the sense of "consisting of" means that it is the essential component which determines the functional properties. This implies that in addition technologically related impurities or technologically related admixtures, the process control during deposition or, z. B. in the sputtering, are useful for target production, may be included. Such impurities or technological admixtures are usually in the range of less than 1%, but may also be a few percent.

The base layer arrangement serves to reduce diffusion processes from the substrate into the layer system located above and here in particular into the functional layer arrangement. In addition, it can also be used for anti-reflection and / or increase in the transmission and / or adjustment of the color impression.

For example, in particular for temperable layer systems, the base layer of silicon nitride Si ₃ N ₄ arranged directly on the substrate can be made. This base layer largely prevents diffusion of sodium ions into overlying layers, especially during annealing, thereby contributing to the stability of the layer system.

Since undesired diffusion processes can also already take place during the subsequent deposition processes as a result of the heat input into already deposited layers, the described advantages can be achieved with the base layer even in the case of layer systems which are not to be tempered.

Alternatively, other materials may be used for the layers of the basecoat assembly. For non-temperable layer systems, it is also possible, for example, to use titanium dioxide TiO ₂ as base layer material. But it can also be other dielectric oxides, nitrides or oxynitrides such. As SnO _2, AlN or ZnSnO be used. ₃

Optionally, on the directly on the substrate arranged base layer, a further layer in the form of an adhesive or leveling layer, for. B. of silicon oxide, titanium dioxide, or aluminum nitride. The use of titanium dioxide leads to an increase in the transmission of the layer system.

The functional layer arrangement arranged above the base layer arrangement comprises a zinc oxide-containing seed layer. Zinc oxide-containing means that it can be both an intrinsic zinc oxide layer and a doped zinc oxide layer. Preferably, the seed layer consists of aluminum-doped zinc oxide, which was deposited by means of a sputtering process from a target with an aluminum content of about 2 wt .-%.

The seed layer (also referred to as seed layer) is formed as a layer which influences the layer structure of the functional layer during the deposition in such a way that the desired, low sheet resistance is achieved. The preferred layer thickness of the seed layer is between 7 nm and 10 nm, but it can also assume other values if required, for example being only 2 nm thick.

Above the seed layer, a silver-based functional layer for reflection of IR radiation is arranged. That is, of the incident solar radiation of the radiation fraction with wavelengths in the IR range is largely reflected, while the radiation is transmitted with wavelengths in the visible range.

Silver-based means that the functional layer contains silver over the entire thickness of the functional layer and the optical properties of the functional layer are predominantly determined by silver. Optionally, other IR-reflecting materials such as copper or gold may be admixed or formed as partial layers, so that the functional layer is at least partially composed of a corresponding alloy or partial layers of different metals.

According to the invention, the functional layer has a varying oxidation number of the silver over the layer thickness, wherein the uppermost layer thickness region, i. H. the thickness range furthest away from the substrate is formed by a purely metallic layer, in particular without oxygen or nitrogen-containing components, and the oxidation number increases in the direction of the substrate.

Oxidation in the present context is understood in the general sense to mean any chemical reaction in which an atom, ion or molecule gives off electrons, without restriction to the formation of oxides. However, the reaction with oxygen is a preferred embodiment, so that the layer thickness ranges contain increased compared to metallic silver oxidation number of silver oxides. An increase in the oxidation number of the silver can alternatively be achieved by the formation of silver nitrides or a mixture of silver nitrides and silver oxides.

The term "oxidation number" is understood to mean the average oxidation number which results within a layer thickness range of optionally differently oxidized silver.

The variation of the oxidation number can be realized either by corresponding partial layers with a uniform oxidation number for each partial layer or by a gradient layer with grading oxidation number. A combination of one or more gradient layers with one or more partial layers is also possible. A gradient layer can also be regarded as a layer consisting of several partial layers, with the layer thickness of the respective partial layer approaching zero.

Layer thickness range is understood to mean an area that expands over the entire layer viewed parallel to the substrate and also has uniform properties considered perpendicular to the substrate. In the case of the construction of the functional layers of partial layers corresponds to a layer thickness range of a partial layer, in the case of Gradient layer of a layer with a zero thickness layer thickness.

By increasing the oxidation number in the direction of the substrate and thus also in the direction of the seed layer, the adhesion at the interface between seed layer and functional layer and thus the stability of the entire layer system against mechanical stresses is significantly improved. In particular, it is no longer possible to rub away the layers arranged above the seed layer with an ethanol-impregnated cloth. This facilitates, for example, the cleaning of architectural glazings coated with the layer system according to the invention during processing for insulating glazing. In addition, the improved adhesion also contributes to the reduction of scratch sensitivity, as otherwise scratches due to lack of adhesion could more easily arise at the interface between germ and functional layer.

The layer thickness range is preferably carried out with an oxidation number of the silver which is increased with respect to pure metallic silver with the smallest possible layer thickness, for example 1-5 nm, since this generally results in an undesirable increase in surface resistance. Depending on the specific application, therefore, an optimization of the layer system with a compromise between improved adhesion by varying the oxidation number and low emissivity by a higher sheet resistance is required.

The cover layer arrangement of the layer system according to the invention comprises at least one dielectric cover layer of a nitride, oxide or oxynitride of a metal, of a semiconductor or of a semiconductor alloy, which serves in particular for the mechanical and chemical protection of the layer system and the antireflection coating. Silicon-containing cover layers are preferably used for this purpose.

The substrate forms a transparent, dielectric material, in particular glass or a polymer material.

The layer system according to the invention is suitable both for applications in which tempering takes place and for applications without tempering. An adaptation for use as a low-E-Sun layer system is possible only by adjusting individual layer thicknesses.

The advantages and embodiments described for single-low-E layer systems can also be applied analogously for a variant with two or more functional layer arrangements, each with its own functional layer, of which at least one, alternatively also several, has the described functional layer arrangement according to the invention.

The individual functional layer arrangements may have the same structure, but may also differ with regard to the materials used and / or the layer thicknesses and / or any additional layers.

The separation between two functional layer arrangements and consequently also their connection to each other is effected by an interlayer arrangement, so that the layer sequence comprises a functional layer arrangement, via an interlayer arrangement and a further functional layer arrangement and optionally further, alternating intermediate and functional layer arrangements. An interlayer array may each comprise one or more interlayer dielectric layers. For example, interlayer assemblies include a zinc stannate layer or a silicon nitride layer or an aluminum nitride layer.

Layer systems with a plurality of functional layer arrangements serve, as described above, primarily to improve the optical and thermal properties of the layer system.

According to one embodiment variant, at least one silver-based functional layer directly adjoins the zinc oxide-containing seed layer of the respective functional layer arrangement. This ensures a particularly good adhesion of both layers to each other.

The layers of the layer system according to the invention are successively deposited from the gas phase by means of vacuum coating in a continuous process on a dielectric substrate or an already deposited layer. The deposition of at least one of the layers, preferably of all layers, takes place by means of DC or MF magnetron sputtering. Optionally, the sputtering may also be pulsed, for example, unipolar or bipolar pulsed.

In particular, the deposition of at least one silver-based functional layer can take place by means of DC or MF magnetron sputtering, during which deposition small amounts of a reactive gas are introduced into the sputtering gas atmosphere, which usually contains argon as the main constituent.

The introduced reactive gas serves to oxidize the silver, in that the silver reacts at least partially with the reactive gas during the sputtering process. Because the composition of the sputtering gas atmosphere is very precise can be influenced, the reactive gas inlet is particularly well suited to set a certain oxidation number. By gradually or gradually changing the composition of the sputtering atmosphere during the sputtering process, it is possible to produce both a functional layer consisting of several partial layers with different oxidation numbers of the silver and a gradient layer with grading oxidation numbers of the silver with little technical outlay.

According to one embodiment, it is provided to introduce nitrogen and / or oxygen as the reactive gas. This allows the deposition of silver oxides or silver nitrides, which have a particularly good adhesion to the seed layer. In addition, oxygen and nitrogen inlets are usually present at sputtering chambers, so that no modifications to existing plants are required. Optionally, an increase in sheet resistance associated with the oxidation of the silver may be compensated for by an increase in sputtering power.

The proportion of the reactive gas based on the indicated in Standard cubic centimeters per minute (sccm) inflow into the corresponding sputtering chamber should be less than 5%, preferably between 1 and 2%. This avoids excessive oxidation of the silver, which would lead to an undesirable increase in surface resistance.

According to one embodiment, the deposition of at least one silver-containing functional layer by means of DC or MF magnetron sputtering of two magnetrons, whereby a two-part layer is made possible in a simple manner.

In particular, when two magnetrons are used, it makes sense to admit the reactive gas only in the gas space of the first magnetron in the direction of passage. As a result, the layer thickness region of the functional layer facing the seed layer is oxidized more strongly, while the second magnetron serves to deposit a purely metallic silver-based layer thickness region. This allows a particularly good setting of the oxidation numbers, which is of great advantage, in particular with regard to an optimization with regard to adhesion on the one hand and optical and electrical properties on the other hand.

It is also advantageous if the sheet resistance of the functional layer is adjusted by means of the sputtering power of the second magnetron in the direction of passage, since even for this no conversions are required and the sputtering power can be set very accurately. This results in preferably the same settings a preferred lower power for the first magnetron with reactive gas inlet and a higher power for the second magnetron without reactive gas inlet.

In the following, the invention will be explained in more detail with reference to an embodiment. The accompanying drawings show in

1 an inventive single-low E-layer system.

According to an exemplary embodiment, a single-low-E layer system according to the invention is applied to a glass substrate, wherein all layers are deposited by means of magnetron sputtering. On the glass substrate S, first of all a base layer arrangement GA consisting of a dielectric base layer GAG of silicon nitride is deposited.

Above the base layer arrangement GA, the functional layer arrangement FA is deposited which, viewed upwardly from the substrate, initially comprises a zinc oxide-containing seed layer FAK made of aluminum-doped zinc oxide. Above the seed layer FAK follows the silver-based functional layer FAF, which in the example consists of two partial layers (FAFT1 and FAFT2). Alternatively, an embodiment would be possible as a gradient layer.

The two partial layers FAFT1 and FAFT2 are deposited by two magnetrons with silver targets, wherein, during the deposition into the gas space of the first magnetron in the direction of passage, some additional oxygen is admitted as reactive gas. The proportion of oxygen in the predominantly argon-containing sputtering gas atmosphere is between 1 and 2%, based on the gas inflow in sccm. Accordingly, the first sub-layer FAFT1 of lightly oxidized silver is deposited directly on the seed layer, so that the average oxidation number of the silver in this first sub-layer FAFT1 is greater than zero.

This is followed by the deposition of a purely metallic highly conductive silver layer, in which silver has an oxidation number of 0, in a Sputtergasatmosphäre pure argon. The sheet resistance is set by means of the sputtering power of the second magnetron.

Optionally, a blocking layer can be deposited above the functional layer (FAF).

The layer system is completed at the top by means of the cover layer arrangement, which in the example consists of an arrangement of a 20 nm thick TiO ₂ layer, followed by a 25 nm thick silicon oxynitride layer and as the uppermost cover layer of a TiO ₂ layer with a thickness of 3 nm. Optionally, however, other layer thicknesses or layer materials as well as a different number of layers within the cover layer arrangement are possible.

LIST OF REFERENCE NUMBERS

• S

  substratum

  GA

  Base layer arrangement

  GAG

  dielectric base layer

  FA

  Functional layer arrangement

  FAK

  seed layer

  FAF

  functional layer

  FAFT1, FAFT2, ...

  Sublayers of the functional layer

  THERE

  overlay assembly

  DAD

  dielectric cover layer

  ZA

  Interlayer arrangement

  ZAZ

  interlayer

Claims (10)

 Infrared radiation reflecting layer system on a transparent, dielectric substrate (S) with the following transparent layer arrangements, viewed from the substrate (S) upwards: A base layer arrangement (GA) having at least one dielectric base layer (GAG) made of a nitride, oxide or oxynitride of a metal, a semiconductor or a semiconductor alloy, A functional layer arrangement (FA) with a zinc oxide-containing seed layer (FAK) and a silver-based functional layer (FAF) arranged above it, - wherein the functional layer (FAF) of several partial layers (FAFT1, FAFT2, ...) is constructed with different mean oxidation number of the silver or as a gradient layer with grading mean oxidation number of the silver, starting from a non-oxidized silver layer, the average oxidation number in the direction Substrate increases, - A cover layer assembly (DA) with at least one dielectric cover layer (DAD) of a nitride, oxide or oxynitride of a metal, a semiconductor or a semiconductor alloy. Layer system according to claim 1, further comprising: At least one further functional layer arrangement (FA), which is arranged below the cover layer arrangement (DA) and is separated from an underlying functional layer arrangement (FA) by an intermediate layer arrangement (ZA) with at least one intermediate layer (ZAZ). Layer system according to claim 2, wherein at least two functional layer arrangements (FA) comprise a zinc oxide-containing seed layer (FAK) and an overlying silver-based functional layer (FAF) consisting of several partial layers (FAFT1, FAFT2, ...) with different average oxidation number of the silver or as Gradient layer is constructed with grading average oxidation number of the silver, starting from a non-oxidized silver layer, the average oxidation number increases towards the substrate. Layer system according to one of the preceding claims, wherein at least one silver-based functional layer (FAF) directly adjacent to the zinc oxide-containing seed layer (FAK) of the respective functional layer arrangement (FA). Process for coating a dielectric substrate (S) by continuous-layer vacuum deposition, wherein the layers of an infrared radiation-reflecting layer system according to one of Claims 1 to 4 are deposited successively from the gas phase on the substrate (S) or on a layer already deposited on the substrate (S) be deposited and the deposition of at least one of the layers by means of DC or MF magnetron sputtering. The method of claim 5, wherein the deposition of at least one silver-based functional layer (FAF) by means of DC or MF magnetron sputtering and during this deposition small amounts of a reactive gas are admitted into the sputtering gas atmosphere of the corresponding sputtering chamber. Process according to Claim 6, in which nitrogen and / or oxygen is introduced as the reactive gas. A method according to claim 6 or 7, wherein the proportion of the reactive gas in the gas inlet of the corresponding sputtering chamber is less than 5%, preferably between 1 and 2%. Method according to one of claims 6 to 8, wherein the deposition of at least one silver-based functional layer (FAF) by means of DC or MF magnetron sputtering of two magnetrons and the reactive gas takes place only in the gas space of the first magnetron in the direction of passage. The method of claim 9, wherein the sheet resistance of the silver-based functional layer (FAF) is adjusted by means of the sputtering power of the second magnetron in the direction of passage.

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