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EP-4490335-B1 - IMPROVED PRODUCTION OF AN ENERGY-REFLECTING COMPOSITE

EP4490335B1EP 4490335 B1EP4490335 B1EP 4490335B1EP-4490335-B1

Inventors

  • STRIJCKMANS, Koen
  • DEPLA, Diederik
  • MICHIELS, LUC

Dates

Publication Date
20260506
Application Date
20230309

Claims (15)

  1. A method for the production of a visual light transmitting and infra-red reflecting composite including, adhered to one side of a transparent support, at least one dichroic filter (DF) which filter comprises at least one metal layer that is sandwiched in between two layers of dielectric metal oxide, dielectric inorganic compound or dielectric inorganic salt, wherein the layers of the dichroic filter are deposited sequentially onto the transparent support using sputter-deposition in at least one sputtering chamber, wherein the process comprises, in the sputtering chamber where at least one of the dielectric layers is sputtered, the introduction of at least one inert gas and water, characterised in that the molar flow of the water that is introduced into the sputtering chamber is in the range of 1% to 30% relative to the total molar flow of inert gas that is introduced into the same sputtering chamber.
  2. The method according to claim 1 wherein, in the sputtering chamber in which the at least one of the dielectric layers is sputtered, the total pressure is controlled to be at most 0.005 mbar, preferably the atmosphere in the sputtering chamber comprising argon as the at least one inert gas.
  3. The method according to claim 1 or 2 wherein, in the sputtering chamber in which the at least one of the dielectric layers is sputtered, the partial pressure of water is maintained in the range of at least 0.00001 mbar and 0.0015 mbar.
  4. The method according to any one of the preceding claims wherein the water is introduced into the sputtering chamber as water vapour.
  5. The method according to any one of the preceding claims that is performed in continuous mode whereby a flexible substrate is passed through the process starting from a feed unwinding chamber and ending in a product winding chamber and is in between those chambers passed through a series of sputtering chambers in which the layers of the dichroic filter are subsequently deposited on the substrate.
  6. The method according to any one of the preceding claims wherein the metal layer contains at least one metal selected from the group consisting of silver (Ag), titanium (Ti), copper (Cu), gold (Au), platinum (Pt), palladium (Pd), aluminium (Al), nickel (Ni), chromium (Cr), molybdenum (Mo), vanadium (V) or stainless steel.
  7. The method according to any one of the preceding claims wherein the dichroic filter further comprises at least one intermediate layer located between the dielectric layer and the metal layer, wherein the intermediate layer comprises at least one of the metals or alloys from the group consisting of gold, silver, palladium, platinum, palladium, ruthenium or another precious or platinum group metal, nickel, nickel alloyed with chromium, indium, gallium, antimony, arsenic, aluminium, antimony and/or arsenic together with indium and/or gallium, indium antimonide, gallium antimonide, indium gallium antimonide, indium arsenide, gallium arsenide, indium gallium arsenide and indium aluminium arsenide.
  8. The method according to any one of the preceding claims wherein the dielectric layer comprises at least one non-metallic material that is transparent to both visible and infrared radiation.
  9. The method according to the preceding claim wherein the transparent support is one glass layer of laminated glass, the method further comprising the assembly of the laminated glass.
  10. The method according to the preceding claim wherein the laminated glass is used in a glass sculpture, a photovoltaic panel, a UV protecting panel, or in the construction of a building, a greenhouse, an animal shelter or stable, or of a vehicle, preferably as a window in an architectural application, a vehicle, preferably as a safety glass, a windscreen, as another window, as bulletproof glass or penetration-proof glass, and this in a wagon, a bicycle, a motor vehicle such as a motorcycle, a car, a truck, a bus, a railed vehicle such as a train or a tram, a watercraft such as a ship a boat or an underwater vehicle, an amphibious vehicle such as a screw-propelled vehicle or a hovercraft, an aircraft such as an airplane, a helicopter or an aerostat, or in a spacecraft, in a staircase, in a rooftop, in a floor, a canopy or a beam.
  11. The method according to any one of claims 1-8 wherein the transparent support has a shear modulus at room temperature typical of a flexible material, meaning that the shear modulus is in the range of at most 0.5 GPa and at least 0.1 MPa.
  12. The method according to the preceding claim further comprising the step of providing an adhesive layer on at least one side of the transparent support.
  13. The method according to claim 8 further comprising the step of applying directly on the dichroic filter a protecting film consisting of another flexible film, an acrylate wet coating or a wet coating applied by a method comprising the application of a sol-gel technique.
  14. The method according to any one of claims 11-13 further comprising the step of incorporating the composite as a construction element into a structure, wherein the composite is used in at least one of the following forms: • With two adhesive layers, one on the side of the dichroic filter and one on the opposite side, sandwiched in between two transparent plates, thereby forming an assembly, • With one adhesive layer glued to one side of a transparent plate such as a glass plate, thereby forming an assembly, by means of the adhesive layer that is provided directly on the dichroic filter or alternatively on the opposite side of the composite, • With a protective film stretched in between surfaces 2 and 3 of insulating glass, whereby the surfaces of the insulating glass are numbered according to the standard practice with insulating glass units ("IGU") to number the surfaces starting with giving the exterior surface of the glass unit the number 1 (one), and sequentially increasing the number for the subsequent surfaces that are encountered when one is counting towards the interior surface of the glass unit, thereby forming an assembly, • With a protective film sandwiched between two layers of intermediate plastic that are sandwiched between the two rigid transparent plates, together forming an assembly.
  15. The method according to any one of the preceding claims wherein the composite exhibits the following transmittance characteristics established in accordance with Industry Standard NEN-EN 410, (a) if the substrate carries only one single layer sequence that is able to represent a dichroic filter: • a visible light transmittance ("VLT"), weighted as for the illuminant D65 reference, of at least 40%, and/or • a transmittance in the wavelength range from 900 to 1000 nm ("T_IR"), weighted for the global solar radiation and the weighing factors normalised over the specified wavelength range, that is less than the VLT, preferably the T_IR being at most 80%, and (b) if the substrate carries at least two sequences that are able each to represent a dichroic filter: • a visible light transmittance ("VLT"), weighted as for the illuminant D65 reference, of at least 50%, and/or • a transmittance in the wavelength range from 900 to 1000 nm ("T_IR"), weighted for the global solar radiation and the weighing factors normalised over the specified wavelength range, that is less than the VLT, preferably the T_IR being at most 70%.

Description

FIELD OF THE INVENTION The present invention relates to the production of visually transparent, infra-red reflecting objects comprising a dichroic filter, also known as an interference filter, often addressed as a "stack" because of the sequence of different layers that it typically comprises. The interference stack may be tuned to selectively reflect heat, i.e. infra-red radiation, while transmitting most of the visible light. The object may for instance be a polymeric film or glass plate upon which the stack is deposited as a coating, and such a film or glass plate may for instance be useful as heat mirror for solar heat control with windows in vehicles or buildings. More particularly, the invention relates to an improved process for producing a product offering improved product properties. BACKGROUND OF THE INVENTION Heat-mirrors that reflect radiation in the infrared spectrum while transmitting radiation in the visible spectrum have important applications for example as windows in buildings or vehicles. For transparent heat-mirrors, visual light transmittance must be high, and hence the reflectivity and absorptivity must be low. In the infrared, however, the heat-mirror must have high reflectivity and so transmittance and absorptivity in the infra-red must be low. Heat-mirrors comprising a stack of alternating dielectric and metal layers are known in the art. The interference stack or filter suitable for reflecting heat and/or energy shielding, is typically at most only a few hundred nanometres thick and any physical strength of the overall object must be provided by the substrate that is supporting the stack. An interference stack suitable for use as heat mirror may be obtained by the use of sputter deposition onto a transparent substrate. The applicants prefer to use magnetron sputter deposition for depositing the subsequent layers because this technique has been found the most useful for applying thin film deposits of uniform thickness over large surface areas. Briefly, magnetron sputtering involves transporting a substrate through a series of low pressure zones (or "chambers" or "bays") in which the various film regions that make up the coating are sequentially applied. Metallic films are sputtered from metallic sources or "targets," typically in an inert atmosphere such as argon. To deposit transparent dielectric film, the target may be formed of the dielectric itself (e.g., zinc oxide or titanium oxide). The dielectric film may also applied by sputtering a metal target in a reactive atmosphere. To deposit zinc oxide, for example, a zinc target can be sputtered in an oxidizing atmosphere; silicon nitride can be deposited by sputtering a silicon target (which may be doped with aluminium or the like to improve conductivity) in a reactive atmosphere containing nitrogen gas. Fairly common is also the use of suboxide targets, in combination with a reactive atmosphere. A layer of titanium oxide is often obtained using a suboxide target with formula TiOx in combination with oxygen presence in the sputtering chamber. More details follow later in this document. The thickness of the deposited film may be controlled for instance by varying the speed of the substrate and/or by varying the power on the targets. The interference filter typically has a multilayer structure which may be constructed by sequentially applying the various layers onto the support. The most simple dichroic filter consists of a thin metal layer that is sandwiched between two layers of dielectric material that is characterised by a high refractive index. This structure is able to bring the property of preferentially passing energy of certain wavelengths and reflecting energy of other wavelengths. The structure is most commonly made suitable for transmitting visible light and reflecting electromagnetic radiation in the infrared region, hence for forming a structure that to the human eye looks transparent but is able to reflect heat, e.g. as part of solar radiation. It is believed that the effect is caused by an interaction between the incoming radiation and the cloud of free electrons in the metal layer(s), whereby radiation in some wavelengths is slowed down relative to other wavelengths. But also the dielectric layer plays an active role. The metal layer alone would have a much lower transmittance of visible light and would thus be readily noticeable by the human eye. The dielectric layers allow a significant part of that lost transmittance to be regained in the wavelength range of visible light. The layer of dielectric material may also be called a spacer layer or a boundary layer. The boundary layer(s) offer physical protection to the metal layer, but also reduce visual reflections from the metal layer beneath them. Dielectric materials, also known as "dielectrics", are non-metallic materials which are transparent to both visible and infrared radiation. Some documents state that organic polymers are also suitable for this purpose, but