EP2766751A1

EP2766751A1 - Multilayer systems for selective reflection of electromagnetic radiation from the wavelength spectrum of sunlight and method for producing same

Info

Publication number: EP2766751A1
Application number: EP12769389.3A
Authority: EP
Inventors: Roland Thielsch; Ronny Kleinhempel; Andre Wahl
Original assignee: Southwall Europe GmbH
Current assignee: Southwall Europe GmbH
Priority date: 2011-10-13
Filing date: 2012-09-28
Publication date: 2014-08-20
Also published as: BR112014008831A2; JP2015502559A; MX2014003751A; UA109973C2; US20140233093A1; WO2013053608A1; DE102011116191A1; CN103874939A; SG11201401353RA; AU2012323155B2; CA2848581A1; AU2012323155A1; IL231956A0; AU2012323155C1; KR20140084169A

Abstract

The invention relates to multilayer systems for selective reflection of electromagnetic radiation from the wavelength spectrum of sunlight, and to a method for producing said systems on suitable, preferably polymeric, carrier materials. Such a multilayer system of the invention is formed with at least one layer composed of silver or a silver alloy, which is coated over the whole area on both surfaces with in each case a seed layer and a cap layer. In this case, the seed layer and cap layer are formed from dielectric material. These are ZnO and/or ZnO:X. In this case, at least one such multilayer system is formed on a flexible polymeric substrate, preferably a film which is optically transparent in the visible spectral range.

Description

Multi-layer systems for selective reflection of electromagnetic radiation from the wavelength spectrum of sunlight and method for its production

The invention relates to multilayer systems for selective reflection of electromagnetic radiation from the wavelength spectrum of sunlight and a method for producing this on suitable preferably polymeric carrier materials.

The preferred, but not exclusive, use of such a composite material consisting of said multi-layer systems with said support is the production of laminated laminated glass in conjunction with other polymeric adhesive films and glass.

Another use is a combination of said composite material with other coated or uncoated films and adhesives for use as a "window film" for subsequent application to glazing. Such multilayer systems are used for selective selective influencing of the transmission as well as reflection of electromagnetic radiation emitted by the sun and thereby on substrates which are transparent to the electromagnetic radiation, in particular glass or glass

Polymer films as thin films by per se known vacuum deposition process, in particular PVD method formed. Thus, the goal is connected to reflect the highest possible proportion of radiation in the non-visible range (eg solar energy range, or near-infrared spectral range), so that the proportion of transmitted solar energy is minimized. A particular aim is to maximize the value of the total solar transmission T _T s (calculated according to DIN ISO 13837, case 1) by a composite glazing equipped with such a multilayer system on said support to a maximum of 40%, that of the electromagnetic radiation emitted by the Sun and incident on the Earth's surface. As a result, the heating is minimized inside rooms or vehicles and the energy cost to create a person in the interior pleasant ambient climate can be reduced. In contrast to this, however, the highest possible proportion of the radiation in the region of visible light should not be reflected, as far as possible not absorbed, so that the proportion of solar radiation visible to the human eye (T _vis , calculated in accordance with ASTM E 308 for illumination source A and Observer 2 °) above 70% can be maintained. This requirement for T _v is required by law for vehicle glazing applications.

For this purpose, multilayer systems have been used for a long time, which are formed on substrates (glass or plastic). These may be alternating layer systems in which high and low refractive layers of dielectric materials are formed on each other. Frequently, even thin metal layers are used alternating with thin dielectric layers (oxides and nitrides). These oxides or nitrides should have optical refractive indices at a wavelength of 550 nm in the range 1.8 to 2.5.

Among other reflective metals, such as gold or copper, silver or silver alloys (Ag-Au, Ag-Cu, Ag-Pd and others) which have very good optical properties for these applications are preferably used for the metal layers.

It is advantageous to deposit such a silver or silver alloy layer on a seed layer.

In order to apply a complex multilayer system of a series of oxide layers and Ag layers, it is common for an already deposited / deposited Ag layer to be overcoated with oxides in a reactive sputtering process.

It is known that Ag oxidizes easily in the presence of oxidizing media such as O ₂ or H ₂ O, but especially in a reactive plasma containing these gases. The oxidation is accompanied by a significant deterioration of the properties of the Ag, so that the desired visual and energetic properties of such a multilayer system are generally not achieved without special countermeasures. One prior art protective measure is the application of a very thin layer of metal to the silver layer.

As cover layers, Ti or NiCr alloys with a typical layer thickness <5 nm have mostly been used. This is to avoid the oxidation of the silver on the layer surface, since the direct contact of the

Surface with the oxygen and other reactive constituents of the atmosphere (plasma) can be avoided in the subsequent formation of a dielectric layer. The silver is protected in this form from degradation, whereby the metallic cover layer can oxidize.

Since for the deposition of the thin cover layer a separate coating Station is required in the coating machine, this can not be used for the deposition of dielectic material (which is necessary for the optical effect of the layer system). This generally leads to higher coating time and thus increased coating costs.

In multilayer systems, in general, the interface roughness increases with increasing number of layers. In the case of thin silver layers, this can lead to the second and third silver layers in a multilayer system having inferior electrical and optical properties of comparable thickness. This is indirect, e.g. detectable by measuring the electrical resistance. Additional absorption effects at the rough interface between silver and dielectric layers additionally reduce the transparency for electromagnetic radiation in the wavelength range of visible light.

It is therefore an object of the invention to provide a multilayer system for the applications "glass laminate" for vehicle glazing or "window film", which has improved properties.

These are on the one hand a high transmission and low reflection in the visible spectral range and on the other hand a low transmission and a high reflection of radiation components from the non-visible spectral range (near infrared range).

At the same time, it is a further object of the invention to provide a method suitable for the industrial production of said multilayer system for deposition on a suitable support. In particular, it is an object of this invention to provide a method for a cost effective, roll-to-roll method applicable application to a polymeric substrate.

According to the invention, this object is achieved with multilayer systems having the features of claim 1. A manufacturing method for these multilayer systems is defined by claim 8. Advantageous embodiments and further developments can be realized with features described in the subordinate claims. A multilayer system according to the invention for a selective reflection of electromagnetic radiation from the wavelength spectrum of the sunlight is coated with at least one layer of silver or a silver alloy, which is coated on both surfaces with one seed layer and one cap layer on both surfaces the seed and cover layer are formed of a dielectric material formed. In this case, the seed layer and also the cover layer of ZnO and / or ZnO: X are formed. At least one such multilayer system is formed on a flexible polymeric substrate, preferably an optically transparent film in the visible spectral range. A seed layer and a cover layer can be formed from the pure ZnO, the doped zinc oxide or in each case one of the two layers of the ZnO and the other layer of the doped ZnO. In addition to pure silver, it is also possible to use a silver alloy in which Au, Pd or Cu with small proportions are present. Hereinafter, the layers are generally referred to as a silver layer. For silver alloys, the proportion of additional metal contained should be kept very small, possibly less than 2%. Such a multi-layer system or several of these multi-layer systems may have been formed one above the other on the substrate. In this case, recourse can be had to conventional vacuum coating methods, in particular PVD methods and, with particular advantage, to magnetron sputtering.

The coating on plastic substrates (polymer films) is often used in

Batch operation performed, since these substrates are usually provided in roll form with finite length.

It is advantageous if both the seed layer and the cover layer can be sputtered from the same target material. That is, the same material basically fulfills the corresponding function. In this case, it is possible to adapt the respective gas mixture fed into the coating area, firstly for the seed layer and secondly for the covering layer in each coating step, in order to thus optimize the respective function. This allows a particularly economical forward + backward coating by winding back and forth (with each wrapping is a system with germination). layer - silver - covering layer deposited). The multi-layer system can be produced without time-consuming ventilation operations for hanging the role with multiple silver layers and seed and cover layers. The targets for the formation of the seed layer, the silver layer and the cover layer are arranged successively in the feed axis direction of the substrate. The targets for the formation of the seed layer and the cover layer may be formed of the same material.

If, in the coating, the substrate is wound from roll to roll, depending on the feed direction of the substrate, a seed layer can be formed alternately alternately with one target at a time, and a cover layer can be formed with the opposite feed direction. As a result, in particular in the case of multi-layer systems with several silver layers, which are each enclosed by a seed layer and a cover layer, the time and expense for production can be reduced.

It is not absolutely necessary that several multilayer systems according to the invention are deposited by back and forth winding. Another possibility consists of removing the coated roll after each coating step (for depositing a multi-layer system) and loading the roll onto the original unwinding station and coating same as in the coating step 1.

For the formation of the seed and cover layer mixed oxides ZnO: X with X, for example Al ₂ 0 ₃ , Ga ₂ 0 ₃ , Sn0 ₂ , ln ₂ 0 ₃ or MgO can be used. In this case, corresponding targets with the respective composition, ie pure ZnO or at least one other of the said oxides can be used for the coating. The proportion of these oxides, which is in addition to ZnO contained in the seed and cover layer, should be a maximum of 20% by mass, a proportion of 10 mass% is then preferable to ensure especially the expression of the crystalline structure for the seed layer ,

The seed layer and / or the cover layer should have a layer thickness in the range 5 nm to 15 nm and the silver layer a layer thickness between 5 nm and 25 nm, preferably 10 nm. It is advantageous to be able to form additional dielectric layers which enclose such a multilayer system from both sides.

To realize a multi-silver layer system according to the invention, two or more are in a sequence of coating steps

Monilayer systems, preferably three monoside layer systems according to Figure 2 to deposit on a substrate. A monoseal layer system is a construction of a dielectric layer, a thin seed layer, a silver layer, a cover layer and a final dielectric layer (see FIG. 1).

In order to achieve the desired optical properties, the thicknesses of the silver layers and the thicknesses of the dielectric layers must be adapted.

The dielectric layers have a refractive index of n> 1.8 at a wavelength of 550 nm and lower absorption, and may preferably be formed of ln ₂ 0 ₃ .

A dielectric layer structure formed between two silver layers, which is composed of cover layer, dielectric layer and seed layer, has the effect of a dielectric spacer layer in an optical filter system for defining the position of the spectral transmission range and the color appearance of a laminated glass, as known from the prior art is known. It is of particular advantage according to the invention that the thicknesses of the seed and cover layers contribute to the layer thickness of dielectric spacer layers, since they produce a corresponding optical effect, like other dielectric materials, and contribute to the overall optical effect. The contribution of the seed and cover layer to the dielectric thickness in the layer system can be taken into account with its optical refractive index and geometric thickness in the construction of the multilayer system. The optical refractive index of ZnO at a wavelength of 550 nm is about 1.95 to 2.05, depending on the deposition conditions. It may differ slightly from the proportion of further oxide contained in a germination and / or cover layer. This makes it possible to adapt to the desired optical effect in cooperation with other dielectric layers made of other materials. In the case of the formation of the multilayer systems, three targets can be used in the vacuum coating for the formation of the silver layer and the seed and cover layer, which are arranged successively in the feed axis direction during the coating and / or can be used.

This has the advantage, in particular in the case of a roll-to-roll coating, as is carried out in the batch operation in the coating of film substrates, that the design and the expenditure of time are reduced when forming a layer structure in which several multilayer systems according to the invention are to be formed one above the other can be.

Thus, independently of the direction of movement of the substrate, first a seed layer with a ceramic target ZnO and / or ZnO: X, then the silver layer with a silver target and the cover layer with a second ZnO and / or ZnO: X target can be formed. The process conditions, and in particular the gas composition, which is introduced into the coating layer for seed layer / covering layer can be kept constant or equal in each coating step.

During the formation of the seed and cover layers, the gas mixture used (sputtering gas) should consist of argon, oxygen and hydrogen and have a composition adapted to the seed and cover layer. In this case, the proportion of oxygen and hydrogen in the sputtering gas in a certain range (orientation value is <10%, but may vary by appropriate coating equipment, such as gas inlet and Pumpenanord- tion) are on the one hand, the desired layer structure for optimal, the layer growth of subsequently applied silver layer to achieve positively influencing germination effect and on the other to deposit optically transparent (absorption-free) layers. The coating can be at a typical pressure within the coating range of 0.4-1.0 Pa.

For the topcoat on the silver also a suitable gas composition should be chosen to ensure a sufficient protective effect. In this case, the oxygen concentration is to be kept low (orientation value is <10% based on the total amount of gas). For this purpose, it is additionally advantageous to choose the proportion of hydrogen higher than the oxygen content (Orientation value is <15% based on the total gas quantity).

The inventive use of seed and outer layers of ZnO and / or ZnO: X, the quality of the silver layers can be improved. This can be explained on the one hand by an improved silver growth, and on the other hand by the corresponding protective effect of the covering layer. Another positive influence is the formation of very smooth boundary layers between the seed layer and the subsequent silver layer and between the deposited silver layer and the top layer applied to it.

It is known that due to growth-related structural properties, thin silver layers have properties which still differ considerably from those of the massive material and limit the achievable properties of the layer systems.

The application of a growth-influencing thin seed layer or layer called "seed layer" in the English language is intended to achieve better properties which are more similar to solid Ag by means of a layered growth (layer formation) which begins even at low layer thickness particularly good, since the seed layers of the ZnO and / or ZnO.X have a crystalline structure whose structure has an epitaxial relationship to the structure of the silver.

It is particularly important that the coating conditions allow the seed layer a) predominantly grows up in a crystalline manner and b) at the same time has a certain crystalline preferred direction for the desired orderly growth of the silver layer.

In the case of multilayer coating systems in which several multilayer systems are formed on top of each other, it was also possible to demonstrate via measurement of the sheet resistance that the electrical conductivity of the second, third and also fourth silver layer is comparable to the first one. In other words, it can be shown that the layer quality of the silver layers and thus also the low roughness of the boundary layers in one Layer stack, which consists of several such layer sequences, can be realized (see Figure 3).

Highly efficient sun protection layers for glazing in the automotive industry achieved a target total solar transmission T _TS <40% and T _vis > 70% and R _vis <10%. But there are also layer systems possible, which have a higher R _vis value.

The layer thicknesses of the seed layer and the cover layer (s) can also be chosen so that they are targeted to the interference of certain electromagnetic

Radiation can be used. In multilayer systems with several silver layers, the seed and / or cover layers can also have different layer thicknesses, so that they can cause interference at different wavelengths.

Thus, in the case of an inventive IV system structure with three silver layers each enclosed by a seed and cover layer and dielectric layers on a PET film as substrate and the use of such a coated film in a glass laminate (FIG. 4), a total proportion of transmitted radiation T _T s <40%, the proportion of transmitted

Radiation in the wavelength spectrum of visible light T _vis > 70%, the proportion of the reflected radiation in the wavelength spectrum of visible light R _vis <10% are kept. The invention will be explained in more detail by way of example in the following.

Showing:

Fig. 1 shows in schematic form an example in which a silver layer is enclosed by a seed and cover layer;

Figure 2 is an example in schematic form, in which three silver layers each having a seed and cover layer are present in a multi-layer system construction;

FIG. 3 shows a diagram with calculated and measured electrical areas. chenwiderständen with different numbers of silver layers within a multilayer system and

Figure 4 is a schematic representation of the installation of a multi-layer system according to the invention embedded in a laminated glass plastic film.

The example of a multilayer system with a silver layer 4 shown in FIG. 1 was applied to the PET substrate 1 in a coating step. As a dielectric layer, an ln ₂ O ₃ layer 2 having a layer thickness of 25 nm was applied by magnetron sputtering in a reactive process using metallic indium targets.

In the subsequent coating station, the seed layer 3 was deposited with a layer thickness of 8 nm of a ceramic with 2% Al ₂ 0 ₃ doped ZnO: X target. In each case about 5% oxygen and hydrogen were added to the sputtering gas argon. The deposition of the metallic silver layer 4 of 10 nm was carried out by magnetron sputtering in an argon plasma. For the deposition of the cover layer 5 (layer thickness 7 nm), a ZnO: X target doped with 2% Al ₂ O ₃ was likewise used. The argon in this case 5% oxygen and 8% hydrogen were added. The final dielectric layer 6 of ln ₂ O ₃ with a layer thickness of 30 nm was again realized by a reactive process using metal indium targets.

In the case of one silver layer 4, this sheet silver layer system achieved a surface resistance of 6.2 ohms.

The multilayer system structure with three silver layers 4 shown in FIG. 2, each formed between a seed layer 3 and cover layer 5, was realized by three coating steps. To demonstrate the function of the seed layer 3 and cover layer 5, the multilayer system described for FIG. 1 was coated identically three times on top of one another.

For the realization of the required properties with respect to T _{TS /} T _vis and R _vis , however, the thicknesses of the In ₂ O ₃ layers 2 and 6 as well as the silver layers 4 had to be adapted. The seed layers 3 and cover layers 5 were in each coating step under the same conditions.

FIG. 2 shows a construction in which three multi-layer systems according to the invention, which are each formed with a seed layer 3, a silver layer 4 and a cover layer 5, have been formed on a PET substrate 1. The layer thicknesses and the composition of the seed layers 3 and the cover layers 5 correspond to the example according to FIG. 1.

Thus, the dielectric layer 2 of ln ₂ O ₃ formed on the substrate 1 should have a layer thickness of 20 nm to 50 nm, the dielectric layers of In ₂ O ₃ formed between a seed layer 3 and a cap layer 5 should have a thickness of .mu.m Range 40 nm to 150 nm. The dielectric layer of In ₂ O ₃ formed on the outer surface facing away from the substrate 1 should have a thickness in the range of 20 nm to 70 nm. All silver layers should have a layer thickness in the range of 7 nm to 25 nm.

On the basis of the experimentally determined electrical surface resistance on a multilayer system with a silver layer and a layer thickness of 10 nm, the expected electrical surface resistance was estimated in a parallel connection with further 10 nm thick silver layers. The detected electrical resistances in the multiple silver multilayer system assemblies were compared to theoretically calculated values. The illustration in FIG. 3 clarifies that the calculated values are congruent with the measured values for a two-, three- and four-silver layer system. This confirms that also the second, third and fourth silver layers can be produced in a multilayer system with comparably good silver properties. This situation results from the diagram shown in FIG. 3 and proves that there is no increase in the surface roughness on the silver layers as the number of silver layers increases.

Furthermore, the multilayer system consisting of three multi-layer systems corresponding to one another and designed according to the invention can be optimized by adapting individual layer thicknesses in order to realize the properties T _T s <40%, T _vis > 70% and R _vis <10% in a glass laminate. The construction of the "glass laminate" is shown in FIG 1 is a PET substrate, 7 a multilayer system according to the invention with three silver layers 4, 8 PVB (polyvinyl butyral) layers and 9 glass.

In the example shown in FIG. 4, the layer thicknesses for the seed layers 3 at 8 nm and the cover layers 5 were left at 7 nm. The silver layers 4 had the following thicknesses (starting from the substrate 1) first silver layer = 8.7 nm, second silver layer = 16.9 nm and third silver layer = 13.7 nm. The dielectric layers 6 were made of ln ₂ O ₃ and had the following Thicknesses also starting from the substrate 1 - 1st layer of ln ₂ O ₃ = 24 nm, 2nd layer of ln ₂ O ₃ = 76 nm, 3rd layer of ln ₂ 0 ₃ = 90 nm and 4.

Layer of ln ₂ 0 ₃ = 32 nm.

With this layer system, the following values were achieved in the "glass laminate": T _vis (A, 2 °) = 72.4%

R _vis (A, 2 °) = 9.1%

T _TS (ISO) = 38.1%

Claims

claims

1. multilayer system for selective reflection of electromagnetic radiation from the wavelength spectrum of sunlight, which is coated with at least one layer of silver or a silver alloy, each with a seed layer and a cover layer on both surfaces over the entire surface and the seed and cover layer of a dielectric material are formed on a flexible polymeric substrate,

characterized in that the seed layer (3) and the cover layer (5) of ZnO and / or ZnO: X are formed.

2. Multilayer system according to claim 1, characterized in that X is selected from Al ₂ 0 ₃ , Ga ₂ 0 ₃ , Sn0 ₂ , ln ₂ 0 ₃ and MgO and is contained in a proportion of at most 20% by mass.

3. Multilayer system according to one of the preceding claims, characterized in that the seed layer (3) and / or the cover layer (5) has a layer thickness in the range 5 nm to 15 nm and the silver layer (4) has a layer thickness between 5 nm and 25 nm ,

4. Multilayer system according to one of the preceding claims, characterized in that between a cover layer (5) which is formed on a silver layer (4), and a seed layer (3), which is formed under a further silver layer (4), a layer of a dielectric material, preferably ln ₂ 0 ₃ , is formed.

5. Multilayer system according to one of the preceding claims, characterized in that at least two, preferably three multi-layer systems, each with a silver layer (4) on a substrate (1) are formed one above the other.

Multilayer system according to one of the preceding claims, characterized in that a dielectric layer (2) is formed between a substrate (1) and a multilayer system having a layer thickness in the range 20 nm to 50 nm.

Multilayer system according to one of the preceding claims, characterized in that between multilayer systems each having a silver layer (4) in each case a dielectric layer (6) with a layer thickness in the range 40 nm to 150 nm and / or on the outer, the substrate (1) facing away Surface is formed a further dielectric layer (6) with a layer thickness in the range 20 nm to 70 nm / are.

Method for producing a multilayer system according to one of the preceding claims, characterized in that in a vacuum coating method, in particular magnetron sputtering, targets for the formation of the seed layer (s) (3), the silver layer (s) (4) and the cover layer (s ) (5) are used, which are arranged in the feed axis direction of the substrate (1) successively and thereby the targets for the formation of the seed layer (s) (3) and the cover layer (s) (5) are formed from the same material.

A method according to claim 8, characterized in that the gas mixture which is used for the formation of the seed layer (s) (3) and the cover layers (5), to the respective layer formation for the seed layer (s) (3) and the cover layer (5).

10. The method according to claim 9, characterized in the gas mixture for the formation of the cover layer (s) (5) a smaller proportion of oxygen and a higher hydrogen content, as in the formation of the seed layer (s) (3) is maintained.

Method according to one of claims 8 to 10, characterized in that the substrate is wound in the coating from roll to roll, so that depending on the feed direction of the substrate alternately alternating with one target once a seed layer (3) and in opposite feed direction a cover layer (5) is formed.