WO2012175289A1

WO2012175289A1 - Polymeric substrate material for physical and chemical vapor deposition processes, containing an adhesion-promoting polymeric layer, and the use thereof for producing concentrators of solar radiation

Info

Publication number: WO2012175289A1
Application number: PCT/EP2012/060074
Authority: WO
Inventors: Uwe Numrich; Arne Schmidt; Christoph Steinfels; Sven Balk; Michael Olbrich
Original assignee: Evonik Röhm Gmbh
Priority date: 2011-06-21
Filing date: 2012-05-30
Publication date: 2012-12-27
Also published as: DE102011077878A1

Abstract

The invention relates to a composite molded body and to the use thereof for concentrating solar radiation in solar reflectors against the background of ensuring the required reflection of solar radiation (total solar reflection) in the most sustainable manner possible. The invention relates in particular to a novel substrate material and to coating the same by means of a physical and/or vapor deposition process (PVD/CVD process), for example, and to an adhesion-promoting polymeric layer contained in the composite body. The adhesion-promoting layer assures a lastingly bonding coatability of the reflective coating and an extended service life of the composite molded body.

Description

A polymeric substrate material for physical and chemical vapor deposition processes, comprising an adhesion-promoting polymeric layer, and the use thereof for the production of concentrators of solar radiation

FIELD OF THE INVENTION The invention relates to a composite body and its application to

Concentration of solar radiation in solar reflectors under the background of the most sustainable possible guarantee of the required reflection of solar radiation (total solar reflection).

In particular, the invention relates to a novel substrate material and its coating by means of e.g. a physical and / or chemical vapor deposition process (PVD / CVD process), as well as a contained in the composite body,

adhesion-promoting polymeric layer. The adhesion-promoting layer ensures a permanently adherent reflective coating and an extension of the life of the composite form body. State of the art

Polymer composite moldings in prior art solar reflectors have disadvantages in terms of sufficient weatherability and degradation by ultraviolet (UV) radiation. In particular, for outdoor applications, however, there are high demands on such films in terms of resistance and resistance to UV radiation and other weather conditions. These claims are in particular with regard to dimensional stability, the

Reflectance in the visible or in the near infrared spectrum and the external appearance.

The range of solar radiation relevant for "solar artery" ranges from 300 nm to 2500 nm. However, the range below 400 nm, in particular below 375 nm, should be filtered out to increase the lifetime of the polymeric composite bodies, so that the "effective wavelength range" of 375 nm or from 400 nm to 2500 nm remains. The reflectance of composite moldings in use as flexible

Mirror foil is determined by the quality and durability. Such a laminate can be produced, for example, by vacuum vapor deposition of a flexible polymer film (carrier film) with a thin silver layer. Based on the particularly high reflectance in the relevant compared to other metals

In the wavelength range, silver is the preferred metal for this application. In order to protect the polymeric carrier film and optionally the silver layer against external influences, it is additionally coated with a protective layer. Purpose of this protective layer, which is usually a cover sheet for

Surface treatment is the protection against mechanical abrasion,

Weathering and degradation by UV radiation.

Such a protective system for aluminum mirrors is described in US 4,307,150. As a carrier film, a PET laminate is used, which is vapor-deposited with aluminum and by gluing a (meth) acrylate film against corrosion and

Weather conditions is protected. An explicit UV protection is not considered.

A silver vaporization is much better suited to the construction of such mirrors than an aluminum layer due to the higher degree of reflection. The use of silver is described in US 4,645,714. Silver, in principle, has two disadvantages. On the one hand, especially thin silver layers are particularly susceptible to corrosion. For this reason, protective layers or laminates must be particularly dense. Otherwise, enough small holes or

insufficient tightness at the edge of the laminate to cause unwanted oxidation. On the other hand, both silver and aluminum have one

Absorption gap in the spectral range of ultraviolet light (300-400 nm), especially in the range around a wavelength of 320 nm, which is an important part of sunlight. The permeability is given especially in very thin layers. This short-wave radiation is detrimental to the carrier film and the silver-metal mirror layer, especially for mostly used polyester films or laminates or for the production of laminates, especially in the case of prolonged exposure, as is the case in the field of application of solar mirrors used glue. It can lead to blistering and thus to deformation and to reduce the degree of reflection.

Anticorrosion inhibitors and UV absorption reagents can be incorporated into the protective film listed above for better protection. The most commonly used inhibitors, however, have the disadvantage of exhibiting only reduced weathering or even UV stability and leading to discoloration after some time. However, the latter reduce the reflection in other spectral ranges and thus the efficiency of the solar system.

UV absorbers alone do not contribute to the corrosion protection of

Silver coating, but prevent weather-related aging of the polyester laminate. In order to obtain optimized protection, both components - inhibitor and UV absorber - are separated from each other.

In US Pat. No. 4,645,714, two separate (meth) acrylate-based coatings are applied for this purpose. Polymethacrylates have a significantly higher UV resistance than polyesters. For this, poly (meth) acrylates may be degraded due to thermal instability and lability, e.g. short-wave UV rays emitted due to the process, are not directly coated by means of CVD or PVD processes. The outer contains the UV absorber, the inner contains the inhibitor. By this construction, the inner is protected by the outer layer and it occur to a much reduced extent discoloration. The inhibitor layer is thereby directly on the

Silver vapor deposition applied. The second layer containing the UV absorber again via this first layer. The polyester laminate used is a two-layer coextruded PET film, one layer containing a lubricant to improve flexibility and the other silver vapor-deposited layer containing no lubricant to ensure the smoothest possible surface. The uncoated side of the polyester laminate in turn is coated with a PSA (pressure sensitive adhesive) based on a

Isooctyl acrylate-acrylamide copolymer coated. For example, this coating can be protected with a silicone-coated polyester film prior to using the mirror laminate. However, the (meth) acrylate coatings described in US Pat. No. 4,645,714 and US Pat. No. 4,307,150 both have the disadvantage that they have a reduced weathering stability in outdoor use and thus are generally only poorly suited for outdoor solar applications. These coatings are very poor at watering, abrasion resistant, and have very limited resistance to atmospheric moisture. After erosion of the

Poly (meth) acrylate coating can then be used for the described degradation of the

Polyester laminate come. To avoid this problem, US Pat. No. 5,118,540 adheres an abrasion-resistant and moisture-resistant film based on fluorocarbon polymers. Both the UV absorption reagent and the corrosion inhibitor are part of the adhesive layer with which the film is connected to the metal surface of the vapor-deposited polyester support film. The adhesive layer may again consist of two different layers, analogously to the above-described (meth) acrylate double coating, in order to separate the corrosion inhibitor and the UV absorption reagent from one another.

In contrast, WO 2007/076282 mentions an alternative structure for better protection of the silver coating. The PET carrier film is no longer on the

Surface, but vaporized on the side facing away from the light with silver. On the other side of the PET film, a poly (meth) acrylate protective film is attached, which is equipped with UV absorption reagents. For this purpose, an adhesive layer is required, which causes two further disadvantageous layer interfaces. Additional layer interfaces in turn cause a higher risk of delamination of the film composite, as well as a reduction in the precision of the concentration of solar radiation. Furthermore, the process with the steps of producing PET carrier film, vapor deposition, production of poly (meth) acrylate film and lamination is complicated and therefore makes little sense from an economic point of view. The reverse side of the silver vaporization can either be provided directly with a pressure-sensitive adhesive (PSA) or coated with an additional layer of copper to improve the corrosion resistance on the back and for better adhesion of the PSA. Because of this, there is a great interest in PMMA-based support materials for composite molded bodies, which are permanently adherently adherently coated by means of CVD or PVD.

Due to the lability of the PMMA to high temperatures as well as very short-wave UV rays with wavelengths smaller than that of solar radiation, as e.g. arise during sputtering, is a sustainable adhesion

Direct coating is not possible when using PMMA substrates. Due to this thermal instability, degradation of the PMMA interface would occur, which in turn would result in the formation of liquid or gaseous degradation products within this interface, which is essential for the successful performance of an adherent coating. The required sustained optical quality of the composite molded articles would not be attainable for a solar mirror application due to liability deficits and delamination phenomena. The same applies to adhesion-promoting layers, which are e.g. be applied by CVD or PVD between the support layer and the reflective (mirror) layer.

There is an increasing demand for composite moldings which clearly exceed the existing demands on the longevity or performance preservation of the established composite moldings.

task

The object was to provide a novel composite molded article for solar reflectors with improved or at least equivalent optical properties, the lowest possible number of layer interfaces and improved weathering resistance and optical performance, especially with regard to long-term use. Under long-term use is here in particular an application over a period of more than 10 years, especially more than 15 years, more preferably more than 20 years under particularly strong sunlight

Understood. Furthermore, the object was that the composite body for solar reflectors under particularly strong sunlight, as it occurs, for example, in the Sahara or in the southwestern United States, remains stable for a long time.

This is especially true regarding the intrinsic resistance and filter efficiency of the surface layer of this composite form body against the UV wavelength spectrum between 300 nm and 400 nm.

There was also the task of a composite form of body for

To provide solar reflectors that are simple and cost effective

produce and process is. In particular, the object was to produce an easy to manufacture, as few layers exhibiting system based on PMMA.

In addition, the composite body described as possible

have moisture-resistant, abrasion-resistant and dirt-repellent properties

solution

Against the background of the prior art and the described there for long-term applications only inadequate technical solutions, succeeds in the present invention in a manner not readily foreseeable for the skilled artisan, transparent to the metal layer composite form body

improved weathering stability and a long-term stable stable solar reflection to provide over the prior art over a particularly small number of layers and associated few, potentially disturbing layer interfaces.

In particular, a composite form body was surprisingly found, on the one hand can largely consist of PMMA and thus has the great advantages of PMMA and on the other hand at least one applied by PVD, in particular has multiple layers applied by PVD and possibly CVD.

Surprisingly, it has been found that such a composite molded article, without having an adhesive layer, can be realized if there is a second layer between the PMMA layer and the PVD or CVD layers and optionally a third layer on the other side of the PMMA layer. This makes it special

Surprisingly, it is possible to coat PMMA molded articles with lasting adhesion by means of PVD or CVD, and thus to realize a composite mold of high optical quality. In this way, efficient and sustainable use of PMMA in high-end applications, e.g. when

Solar mirror for the concentration of solar radiation in the desert climate, allows.

PMMA has a particularly attractive property profile with regard to the intended applications. So PMMA has an excellent

Weather resistance, excellent optical properties and a

pronounced protective effect against a reflective coating.

The production of films or plates at moderate production costs is possible.

The object is achieved by providing a novel composite form body for concentrating solar radiation in solar reflectors. This composite molding comprises at least the following two or three layers: a first layer which consists of more than 50% by weight of PMMA or a polymer mixture containing PMMA,

- One directly without interlayer on one side of the first layer

applied second layer of polycarbonate or a polyester,

an optional third layer of a fluoropolymer, polycarbonate or

a polyester located on the other side of the first layer,

- And a reflective coating, which is applied directly to the first layer of the opposite side of the second layer and was integrated by means of PVD or CVD body in the composite form. Preferably, the individual layers of the invention

Composite molding the following layer thicknesses: The first layer has a thickness between 6 μηη and 10 cm, preferably between 25 μιτι and 25 mm. Particularly preferably, there are two different embodiments. A composite molding in the form of a flexible film has a preferred layer thickness of the first layer between 6 μιτι and 500 μιτι. The second possible composite shaped body in the form of a plate has a preferred layer thickness of the first layer between 500 μm and 10 cm.

The second layer generally has a thickness between 0.4 μm and 2 cm, preferably between 0.5 and 500 μm, more preferably between 1 and 400 μm, and particularly preferably between 10 and 250 μm. For the optional third layer, the same preferred ranges of possible layer thicknesses apply as for the second layer. In this case, the second and the third layer may be the same thickness or have different thicknesses. For the preferred embodiment of the composite form body as a film, the second and the optional third layer thicknesses each between 0.5 and 500 μιτι. For the equally preferred embodiment as a plate in each case a thickness between 10 μιτι and 2 cm.

Furthermore, in particular composite shaped bodies are preferred in which the first layer is thicker than the second and the optional third layer.

The composite molding according to the invention, in addition to the reflective

Coating further coated by PVD or CVD coatings have. These may be located directly on the reflective coating and / or on the third layer. Furthermore, it can each be several

Acting layers with different functions. The further layers can be, for example, scratch-resistant coatings, UV reflection layers, conductive layers, antisoiling coatings and / or optically functional layers. In turn, the optically functional layers are preferably reflection-enhancing layers. In addition, the layers applied by means of PVD or CVD can be provided with an additional protective layer. In addition to the layers applied by means of PVD or CVD, these protective layers can also be polymer-based, resin-based or sol / gel-based paints. The protective layers can be applied as a solution, reactive resin with subsequent curing, by lamination of a corresponding protective film or by extrusion coating.

Likewise to the composite form bodies, the process for their preparation is part of the present invention. This process consists in particular of the following three to four process steps: In a first process step, the first layer is produced by means of extrusion. The preparation takes place in particular by means of extrusion through a

Slot die as in flat film extrusion, blown film extrusion or solution casting.

In a second method step, the first layer by means of

Extrusion coating provided with the second layer. Preferably, both process steps are carried out simultaneously by means of coextrusion. Alternatively, the production of this two-layer composite can also be effected by means of adhesive-free lamination or later extrusion coating of the first layer with the second layer.

In a third optional method step, this two-layer composite is joined to the third layer. This can also be done simultaneously by coextrusion of all three layers or likewise by a subsequent extrusion coating or tack-free lamination. It is also a method feasible, in which only a composite of the first and third layer is prepared by coextrusion and this composite is then connected by means of extrusion coating or tack-free lamination with the second layer.

Finally, in a third or fourth method step, a reflective coating is applied to the second layer by means of a vapor deposition. The vapor phase deposition is preferably a PVD (physical vapor deposition) or a CVD (chemical vapor deposition).

PVD is the generic term for various physical vapor deposition processes. All these processes have in common that they are vacuum-based coating processes for the realization

in particular thin layers, and that the starting material is transferred by means of physical processes in a gas phase and then deposited on a substrate as a coating by condensation or resublimation. The guide to the substrate surface is usually balistic or along an electric field. Typical working pressures are generally between 10 ^"4 Pa and 10 Pa. A particular surface quality of the coating is usually carried out by the still taking place at the substrate surface diffusion of the deposited particles. PVD agent can not only pure metals

but also, e.g. by supplying oxygen, nitrogen or hydrocarbons, oxides, nitrides or carbides realize. The conversion into the gas phase can be carried out purely thermally or by electron beam, laser beam or arc evaporation.

A second, particularly preferred group in addition to the evaporation process, is the so-called sputtering or Sputterdeposition. During sputtering or cathode sputtering, the starting material is transferred by means of ion bombardment in the gas phase. Variants of sputtering are the IBAD (ion beam assisted deposition or ion beam assisted deposition), by means of which in particular

Order effects within the layer can be effected, the

Magnetron sputtering and ion beam sputtering. Another particularly suitable PVD technique is the ionized dark beam (ICB) technique.

Chemical vapor deposition (CVD), in contrast to PVD, is a process in which the deposition of a solid under

Film formation by a chemical reaction in the gas phase or at the Substrate surface occurs. In general, the raw materials used for this chemical reaction have a significantly lower evaporation temperature than the substance formed in the chemical reaction. By carrying out at a very reduced pressure, such as between 1 and 1000 Pa, a reaction at the substrate surface is preferred to a reaction in the gas phase, which in turn would lead to undesired particle formation. The deposition direction can be performed balistically parallel to the PVD process or influenced by an electric or magnetic field. A variant of CVD which is particularly suitable according to the invention provides the PECVD (plasma enhanced CVD), which can be carried out at lower temperatures, and which is a

An even more gentle variant is the RPECD (remote plasma enhanced CVD). In this variant, the plasma and the substrate are spatially separated from each other.

According to the invention, CVD plays a role in the deposition of further layers on the PVD-produced reflective coating and / or on the optional third layer. The deposition of these further layers can alternatively also be effected by means of PVD. According to the invention, several layers can also be partially produced by means of CVD and partly by means of PVD.

The inventive, novel PMMA-based composite molding for

Solar reflectors have the following properties, in combination as an advantage over the prior art, especially with regard to optical properties, on:

Avoidance of disadvantageous layer interfaces due to the manufacture of the composite mold without the inclusion of further layers, e.g. Adhesive layers, between the PMMA substrate and the reflective coating

- Representation of a composite mold body sustainably high optical quality

- Efficient and sustainable use of PMMA in high-quality or sustainable highly stressed applications, eg as a solar mirror for the concentration of solar radiation in the desert climate

The transparent portion of the composite mold body according to the invention is also particularly neutral in color and does not cloud when exposed to moisture. Of the

Composite molded body also shows excellent weatherability and, with optional equipment with a fluoropolymer surface and / or a

Scratch-resistant equipment, a very good chemical resistance, for example, against all commercial cleaning products. These aspects also contribute to maintaining solar reflection over a long period of time. Likewise, the use of the composite form of the invention for concentrating solar radiation is part of the present invention. The long-lived solar reflectors produced with the composite form part of the present invention. In particular, the composite molding containing

Solar reflectors whose solar reflection within 10 years by a maximum of 8%, preferably by a maximum of 5% and more preferably by a maximum of 3% decreases. The material according to the invention can thus also have a very long period of at least 10 years, preferably even at least 15 years, more preferably at least 20 years in places with particularly many hours of sunshine and particularly intense solar radiation, such as. used in the southwestern United States or the Sahara in solar reflectors.

In addition, the composite form of the invention is particularly body

moisture-stable. Thus, this does not show the known susceptibility to delamination of a reflective coating from the PMMA layer under the influence of moisture. PMMA and the reflective coating have different coefficients of thermal and hygroscopic expansion, so that, in the presence of moisture, due to these very different coefficients of expansion, the adhesion between the reflective coating and PMMA is known to be reduced and thus performance-detrimental

Delamination phenomena would occur. This disadvantage has been eliminated by the inventive structure of the composite form body. Detailed description of the layer structure of the invention

Composite molding

The PMMA-containing First Layer The first layer according to the invention is at least 50% by weight, preferably at least 80% by weight, of a layer of PMMA or a PMMA-containing polymer mixture. However, with the formulation PMMA or PMMA-containing layer, the layer is not restricted to pure methyl methacrylate compositions or a single-layer structure. Rather, the PMMA in the first layer may contain comonomers, which need not necessarily be methacrylates. Also, this layer of blends of various plastics, which need not contain all methacrylates, be composed. For example, this layer may additionally contain elastomers, e.g. a polyacrylate elastomer, for impact modification. In addition, this layer can be composed of more than two layers. Not all of these layers necessarily contain methacrylates.

Polymethyl methacrylate plastics are generally obtained by free radical polymerization of mixtures containing methyl methacrylate. in the

In general, these mixtures contain at least 40% by weight, preferably at least 60% by weight and more preferably at least 80% by weight, based on the weight of the monomers, of methyl methacrylate. In addition, these mixtures for the preparation of polymethyl methacrylates may contain further (meth) acrylates which are copolymerizable with methyl methacrylate. The term (meth) acrylates include methacrylates and acrylates as well as mixtures of both. These monomers are well known.

In addition to the (meth) acrylates set out above, the compositions to be polymerized may also contain other unsaturated monomers which are copolymerizable with methyl methacrylate and the abovementioned (meth) acrylates. These include, inter alia, 1-alkenes, such as hexene-1, acrylonitrile; Vinyl ester, like for example, vinyl acetate; Styrene or α-methylstyrene. In general, these comonomers in an amount of 0 wt .-% to 60 wt .-%, preferably 0 wt .-% to 40 wt .-% and particularly preferably 0 wt .-% to 20 wt .-%, based on the weight of the monomers used, wherein the compounds can be used individually or as a mixture.

The PMMA-based first layer used according to the invention may, as already described, contain an impact modifier. A closer one

Description of these impact modifiers can also be found in WO

2007/073952. In a particular embodiment of the invention, instead of pure PMMA-containing layers, PMMA / PVDF blends or PMMA / PVDF two-layer systems may also be used as the first layer. PVDF (polyvinylidene fluoride) as a component of a polymer blend or as an additional layer has several advantages: PVDF has a high chemical resistance and low

Surface energy and an extremely good weather resistance. Thus, PVDF is water-repellent and shows even with long-term use almost no algae growth, comparable to biocidal materials.

The ratio of poly (meth) acrylate to polyvinylidene fluoride ranges from 1: 0.1 to 1: 1 by weight. The PVDF polymers used in the context of the invention are polyvinylidene fluorides, which are generally transparent, partially crystalline, thermoplastic fluoroplastics. Basic building block for the

Polyvinylidene fluoride is vinylidene fluoride, which in high purity water under controlled pressure and temperature conditions by means of a special

Catalyst is polymerized to polyvinylidene fluoride. The vinylidene fluoride in turn is accessible, for example, from the base materials hydrogen fluoride and methyl chloroform, via the intermediate chlorodifluoroethane. In principle, all types of PVDF available on the market can be used with great success in the context of the invention. These include Kynar ^® - types of manufacturer Arkema, Dyneon ^® - types of manufacturer Dyneon and Solef ^® - types of manufacturer Solvay.

The Stabilizer Package (light stabilizer) Preferably, the first layer, and optionally the second and / or third layer contains a stabilizer package consisting of a mixture of UV absorbers and UV stabilizers, more preferably consisting of at least one triazine UV absorber and at least one HALS UV stabilizer. Furthermore, further UV absorbers, e.g. Benzotriazoles, be included. In general, light stabilizers are well known and are described in detail, for example, in Hans Zweifel, Plastics Additives Handbook, Hanser Verlag, 5th edition, 2001, p 141 ff. Sunscreens are to be understood as UV absorbers, UV stabilizers and free-radical scavengers. For example, UV absorbers can be selected from the group of substituted benzophenones, salicylic acid esters, cinnamic acid esters, oxalanilides, benzoxazinones, hydroxyphenylbenzotriazoles, triazines or benzylidene malonate. The preferred representative of UV stabilizers / radical scavengers is the group of hindered amines (HALS).

The first layer may preferably contain between 0% by weight and 10% by weight, preferably between 0% by weight and 6% by weight and more preferably between 0% by weight and 4% by weight of the benzotriazole type UV absorbers,

between 0.1% by weight and 10% by weight, preferably between 0.2% by weight and 5% by weight and more preferably between 0.5% by weight and 3% by weight of the UV absorbers of

Triazine type and between 0.1% by weight and 5% by weight, preferably between 0.5% by weight and 3% by weight and more preferably between 0.2% by weight and 2% by weight of the UV stabilizers, preferably UV stabilizers from HALS Type included. These

Mixture of UV absorbers and UV stabilizers shows over a wide

Wavelength spectrum of solar radiation stable, long-lasting UV protection. As further costabilizers it is also possible to use disulphites, for example sodium disulphite, or sterically hindered phenols and phosphites.

The Thermoplastic Second Layer The thermoplastic second layer is located on one side of the first layer and has the reflective coating on the side opposite the first layer. In a preferred embodiment, the second layer is located in a solar reflector made therefrom on the side of the first layer facing away from the sun. In this case one speaks of a backside mirror. In a front mirror, the second layer is on the sun-facing side.

According to the invention, the second layer has two compelling properties

exhibit. On the one hand, the second layer together with the PMMA-containing first layer without intermediate layer, such as e.g. an adhesive layer, a sustainable stable laminate to be produced. Furthermore, the second layer must be e.g. with inorganic materials, for the construction of the reflective coating by means of PVD or CVD, without an additional primer layer or

Surface treatment sustainable adherent coating. In addition, the layer must be highly transparent and heat-resistant and preferably have a high flexibility. The reflective coating should have no loss of adhesion over a long period of time.

According to the invention, it is necessary to have a high compatibility between PMMA on the one hand and the material selected for the second and the optional third layer on the other hand. Only such materials are suitable for carrying out the invention, from which a stable bond without loss of adhesion can be produced with PMMA.

Particularly suitable for meeting the conditions mentioned are thermoplastic layers of a polyester or polycarbonate. The usable polyester layers are, in particular, coextruded polyethylene terephthalate (PET) layers.

The Reflecting Coating The reflective coating is a functional multi-layer structure shown as a medium PVD and / or CVD, which includes a metal mirror layer, preferably of silver, a silver alloy or aluminum.

On the side facing away from the solar radiation, the metal mirror layer is optional and preferably coated with a second metal layer, for example made of copper or a nickel-chromium alloy. This essentially serves as protection of the metal mirror layer against corrosion, as well as for better adhesion of an optional pressure-sensitive adhesive layer.

In the case of mirror layers made of aluminum, the comparatively "low" reflection of the aluminum mirror in the relevant wavelength range is increased by the application of so-called "enhancement stack" layers (by means of further "physical vapor deposition").

In addition, "enhancement stack" layers can also be used analogously

Silver mirror layers are used for further reflection improvement. This enhancement stack layer structure also acts as an active one

Protective layer or Mifgrationssperre against the silver, and may also act UV-reflective with appropriate design.

Furthermore, the metal mirror layer can additionally be equipped with a primer layer for improving the bond on the second layer. This is usually a metallic or metal oxide layer. The optional thermoplastic third layer

The requirements for the optional third layer are in principle the same as those applied to the second layer. The third layer is preferably applied in the composite form body on the sun-facing side of the first layer. The main purpose is to provide a surface coating with further preferred inorganic coatings, which are not the

Metallic mirror coating, by means of PVD or CVD. In these

Coatings are for example - as already stated - to

Scratch-resistant coatings, UV-reflecting layers, conductive layers,

Antisoiling coatings and / or optically functional layers, such as

For example, anti-reflective or reflection-enhancing layers.

The third layer may be identical in material or thickness to or different from the second layer.

In addition to polyesters or polycarbonates, it is also possible to use fluoropolymers, in particular PVDF (polyvinylidene fluoride), for the third layer. PVDF has high chemical resistance and low surface energy. In addition, PVDF water repellent and shows even with long-term use almost no algae growth, comparable to biocidal materials and thus is very well suited for surface treatment of the composite mold body according to the invention.

Very thin PVDF layers with a layer thickness between 1 μηη and 20 μητι, preferably between 1 μηη and 10 μηη can also be realized with a high transparency.

Furthermore, the same applies to the PVDF in the third layer, as was already carried out for the PVDF as a blend component of the first layer.

The other (inorganic) layers In the case of the others already executed by PVD or CVD

Layers which may be directly on the reflective coating and / or on the third layer are in particular

Scratch-resistant coatings, UV-reflective layers, conductive layers, antisoiling coatings and / or optically functional layers act.

The term scratch-resistant coating is understood in the context of this invention as a collective term for coatings which are used to reduce a

Surface scratching and / or to improve the abrasion resistance can be applied. For the inventive use of composite form body in solar reflectors in particular a high abrasion resistance is of great importance. Another important feature of scratch-resistant coating in the broadest sense is that this layer has the optical properties of the

Film composite did not change negatively. These scratch-resistant coatings are e.g. silicon oxide layers applied directly by PVD or CVD.

The conductive layers are metal oxide layers, e.g. made of indium tin oxide (usually abbreviated ITO). These have the purpose of preventing electrostatic charges. This has both in the operation of the solar reflectors, e.g. in terms of dusting, as well as in the processing of the composite form of great advantages. In addition, ITO has the great advantage of being additionally reflective, especially for radiation in the infrared range. In addition to ITO, it is also possible to use, for example, antimony-doped or fluorine-doped tin oxide and aluminum-doped zinc oxide.

In addition, the surface of the coversheet may be provided with an antisoiling coating, so-called anisoiling coating, to facilitate cleaning. This coating can also be applied by means of PVD or CVD.

The application of titanium dioxide causes, after appropriate stimulation by the UV component of solar radiation, a catalytic degradation of superficial spores and algae. In turn, the optically functional layers are preferably reflection-enhancing dielectric layers. These are constructed, for example, of silicon dioxide and titanium dioxide alternating layers. However, it is also possible to use magnesium fluoride, aluminum oxide, zirconium oxide, zinc sulfide or praseodymium titanium oxide. Depending on the structure, these layers can also be used simultaneously

Scratch resistant coating and / or UV-reflective effect.

Further (organic) layers

Optionally, further, usually organic, in particular polymeric protective layers can be applied to the layers applied by means of PVD by means of extrusion coating, lamination or coating.

For example, these layers applied as a lacquer can likewise be scratch-resistant coatings. As such, polysiloxanes such as CRYSTALCOAT ™ MP-100 from SDC Techologies Inc., AS 400 - SHP 401 or UVHC3000K, both from Momentive Performance Materials, can be used in particular. These paint formulations are e.g. about rollcoating,

Knifecoating or flowcoating applied to the surface of the film composite or cover sheet.

Detailed description of use

Use the composite form of the invention, especially in concentrators preferably in concentrators for the concentration of solar radiation in solar thermal or photovoltaic systems.

The concentration of the solar radiation can be done on the 2-dimensional geometry of a photovoltaic cell, on a Stirling engine or a thermal receiver of a solar arthropod plant. Furthermore, the solar radiation can be concentrated on an absorber tube of a solar thermal collector. For all embodiments, both flat plates, as well as preferred curved shapes can be produced and installed in solar thermal system. The molding can be carried out after the preparation of the concentrators and the subsequent cutting, for example under cold bending or thermoforming, wherein a cold bending process is preferred.

As an alternative to use in concentrators, the composite moldings according to the invention can also be used for the application of a metal decoration design for decorative purposes. More concrete examples are a firm one

Metal (frame) application on PMMA semi-finished products, as they can be used for the production of (mobile phone) displays, or for decoration purposes in the field of automotive or electrical appliances.

Moreover, the composite moldings according to the invention can be used elsewhere as a reflecting surface, e.g. as a traffic mirror in the context of road traffic control systems.

Examples

Measurement Methods a) Initial TSR measurements according to ASTM G 159 b) Adhesive strength was measured in the initial state by means of the cross hatch test according to ISO 2409, using adhesive bond tape of 0.7 N / mm. c) The investigation of the adhesive strength of the reflective coating was carried out after 48 h humidity and temperature at 65 ° C in distilled water by means of the "180 ° Peeltest" according to ISO 1 1339th

Front-panel mirror

Example 1: Front Plate Mirror with "Standard" Reflective Coating

A 4 mm thick composite panel, consisting of 3.9 mm PMMA Plexiglas 7 H and 0.1 mm polycarbonate Makroion 2607, is produced by means of adapter coextrusion.

Thereafter, the application of the reflective coating by means of a plasma-assisted sputtering process to the polycarbonate side of the composite plate, consisting of, in this order, 200 nm Ni / Cr, 100 nm Ag and 5 nm ZAO _x (substoichiometric zinc-aluminum oxide).

Subsequently, the lamination of a 65 μιτι thick surface coating film Plexiglas 0F038 on the reflective coating. This will be in advance

marketable acrylate-based adhesive system applied in a layer thickness of 25 μιτι.

The result is a TSR of 93.4% and a cross-cut adhesion "GT 0", both measured in the initial state, as well as a continued complete adhesion of the reflective coating in the "180 ° Peeltest" after 48 h storage in distilled water at 65 ° C. ,

Example 2: Front side plate mirror with improved reflection coating

Then the application of the reflective coating by means of a plasma-assisted sputtering process on the polycarbonate side of the composite panel, consisting of, in this order, 200 nm Ni / Cr, 100 nm Ag, 0.6 nm ZAO _x , 30 nm S1O2 and 20 nm ΤΊΟ2.

The result is a TSR of 93.9% and a cross-cut adhesion "GT 0", both measured in the initial state, as well as a continued complete adhesion of the reflective coating in the "180 ⁰ Peeltest" after 48 h storage in distilled water at 65 ° C. ,

Comparative example: Front panel mirror

Analogous to Example 1, however, the production of the 4 mm composite panel is completely made of PMMA Plexiglas 7H without polycarbonate layer. The result is a TSR of 93.4% and a cross-cut adhesion "GT 0", both measured in the initial state, and a complete loss of adhesion of the reflective coating in the "180 ⁰ Peeltest" after 48 h storage in distilled water at 65 ° C.

Backside sheet mirror

Example 3: Backside foil mirror with "standard" reflective coating

0.15 mm thick composite foil, consisting of 0.125 mm PMMA plexiglass 7 H, which contains 2% CGX 006 and 0.6% Chimasorb 1 19 for the purpose of UV addition, as well as 0,025 mm polycarbonate Makroion 2607, is manufactured by adapter-coextrusion.

Then the application of the reflective coating by means of a

Plasma-based sputtering process on the polycarbonate side of the composite film, consisting of, in this order, 0.5 nm ZAO (zinc-aluminum oxide), 100 nm Ag and 50 nm Cu.

The result is a TSR of 94.3% and a cross-cut adhesion "GT 0", both measured in the initial state, as well as a continued complete adhesion of the reflective coating in the "180 ° Peeltest" after 48 h storage in distilled water at 65 ° C. ,

Example 4: Backside foil mirror with alternative "standard" reflective coating

A 0.15 mm thick composite film consisting of 0.125 mm PMMA Plexiglas 7 H, which contains 2% CGX 006 and 0.6% Chimasorb 1 19 for the purpose of UV addition, and 0.025 mm polycarbonate Makroion 2607, is produced by means of adapter coextrusion.

Then the application of the reflective coating by means of a

Plasma-based sputtering process on the polycarbonate side of the composite film, consisting of, in this order, 2 nm TiO _x (substoichiometric titanium oxide), 140 nm Ag and 50 nm Cu.

The result is a TSR of 93.8% and a cross-cut adhesion "GT 0", both measured in the initial state, as well as a continued complete adhesion of the reflective coating in the "180 ° Peeltest" after 48 h storage in distilled water at 65 ° C. ,

Comparative Example 2: Backside Foil Mirror Analogous to Example 3, however, the production of the 0.15 mm composite panel is made entirely of PMMA Plexiglas 7H without polycarbonate layer.

The result is a TSR of 94.3% and a cross-cut adhesion "GT 0", both measured in the initial state, and a complete loss of adhesion of the reflective coating in the "180 ° Peeltest" after 48 h storage in distilled water at 65 ° C.

Claims

claims

1 . Composite shaped body for use in solar reflectors for the concentration of solar radiation, characterized in that it is in the

Composite molding is a composite of at least two or three layers, it being at

the first layer to more than 50% by weight of PMMA or a PMMA-containing polymer mixture,

in the second layer, a layer of polycarbonate or a

Polyester located on one side of the first layer

the optional third layer is a layer of a fluoropolymer, polycarbonate, or a polyester located on the other side of the first layer, and the second layer has a reflective coating that is on top of the first layer

located opposite side, and was applied by means of PVD or CVD on the composite molding.

2. Composite molding according to claim 1, characterized in that the reflective coating is a silver, silver alloy or

Aluminum layer contains.

3. Composite molding according to claim 1 or 2, characterized in that there are further applied by means of PVD or CVD coatings on the reflective coating and / or the third layer.

4. Composite molding according to one of claims 1 to 3, characterized

characterized in that the first layer has a thickness between 6 μιτι and 10 cm, the second layer has a thickness between 0.5 μιτι and 2 cm and the optional third layer has a thickness between 0.5 μιτι and 2 cm, wherein the first layer thicker as the second and optional third layer.

5. Verbundfornn body according to one of claims 1 to 4, characterized

in that the first layer contains a mixture of UV absorbers and UV stabilizers, consisting of at least one triazine UV absorber and at least one HALS UV stabilizer.

6. composite molding according to any one of claims 1 to 5, characterized

in that the first layer of PMMA or a PMMA-containing polymer mixture is composed of polyvinylidene fluoride and contains UV stabilizers and UV absorbers.

7. Composite form body according to claim 3, characterized in that the further layers are scratch-resistant coatings,

Weathering layers, conductive layers, antisoiling coatings and / or optically functional layers is.

8. composite mold body according to claim 7, characterized in that it is the reflection-enhancing in the optically functional layers

Layers acts.

9. Composite molding according to any one of claims 1 to 8 in the form of a film, characterized in that the first layer has a thickness between 6 and 500 μιτι and the second and the optional third layer each having a thickness between 0.5 and 500 μιτι wherein the first layer is thicker than the second or the optional third layer.

10. Composite molding according to any one of claims 1 to 8 in the form of a plate, characterized in that the first layer has a thickness between 500 μιτι and 10 cm and the second and the optional third layer each having a thickness between 10 μιτι and 2 cm.

1 1. Composite molding according to at least one of claims 1 to 10,

characterized in that the applied by means of PVD or CVD layers are provided with an additional protective layer.

12. A method for producing a composite molding according to claim 1, characterized in that the first layer is prepared by extrusion and connected by means of coextrusion, adhesive-free lamination or extrusion coating with the second and optionally with the third layer, and that subsequently to the second layer reflective coating is applied by PVD or CVD.

13. The method according to claim 12, characterized in that on the

reflective coating by PVD or CVD one or more further layers are applied.

14. The method according to claim 12 or 13, characterized in that one or more further layers are applied to the third layer by means of PVD or CVD.

15. The method according to any one of claims 12 to 14, characterized

in that a protective layer is additionally applied to the layers applied by means of PVD or CVD by means of extrusion coating, lamination or lacquering.

16. Use of a Verbundfornn body according to one of claims 1 to 1 1 for the concentration of solar radiation in solar reflectors.

17. Use of a composite mold body according to one of claims 1 to 1 1 for application of a metal decoration design for decorative purposes, as a reflective surface in the automotive industry or in electrical appliances or as a traffic mirror in the context of road traffic control systems.

18. Long-life solar reflector, comprising a composite molding according to any one of claims 1 to 1 1, characterized in that the solar reflection within 10 years by a maximum of 8%, preferably by a maximum of 5% and more preferably by a maximum of 3% decreases.