Transparent multilayer system

Abstract

The present invention relates to a transparent multilayer system comprising a layer L1 and a layer L2, wherein layer L1 is made of a transparent material and has at least one surface with a microstructure that provides layer L1 with glare control properties, and layer L2 is made of one or more transparent materials that provide layer L2 with anti-reflection properties, layer L2 being on the surface of layer L1 with the microstructure. The present invention further relates to a method for producing such a multilayer system, its use as a glare control structure, and light-emitting devices and lighting fixtures comprising such a multilayer system.

Description

[Technical Field]

[0001] The present invention relates to a transparent multilayer system with improved glare control, comprising a layer L1 containing a microstructure and a layer L2 formed on the layer L1, and to a method for producing this transparent multilayer system. The present invention further relates to methods of using the transparent multilayer system for optical components and light-emitting devices, such as luminaires and luminaires comprising such transparent multilayer systems. [Background technology]

[0002] Lighting fixtures are ubiquitous in everyday life, providing sufficient light regardless of the time of day. This applies to both indoor and outdoor lighting fixtures, as they are used not only in homes or offices but also outdoors, such as in tram stations. Classic lighting quality characteristics include a sufficient level of illumination, harmonious brightness distribution, prevention of reflections and specular reflections, correct light color, and good color reproduction. Reflection of light rays occurs when light passes from one medium, such as air, to a second medium, such as glass or plastic. The degree of reflection can be calculated using Fresnel's equation. This allows us to determine that the reflectance of yellow-green light with a wavelength of 550 nm is approximately 4% on glass without any anti-reflective coating.

[0003] When light is emitted from a luminaire, some rays leave the luminaire at propagation angles that result in glare, which represent large angles relative to the normal to the emitting surface and can cause discomfort to people in the illuminated space or even violate light regulations (e.g. in an office).

[0004] Glare control structures can be applied to suppress glare beams leaving a lighting fixture and increase the total glare-free luminous flux. Such products are, for example, transparent films or rigid panels containing microstructures on their surfaces, with the smooth surface attached to the lighting fixture. Light rays incident on the microstructures are refracted so that the ray propagation angle is bent toward the normal to the substrate surface of the structure. This narrows the luminous intensity distribution curve of the lighting fixture to low angles and controls glare. Glare control structures are known, for example, from CH711561A1 and CH711562A1, which disclose optical foils containing microstructures with multiple ridges. Such structures are widely used because they reduce glare beams and therefore provide more comfortable light for people in the illuminated area. However, the inventors of the present invention have observed that state-of-the-art structures are insufficient to effectively control glare beams, as glare beams are still observed and can cause discomfort or even violations of light regulations (e.g., in offices). In the past, improvements have been achieved by changing the geometry of the structures, for example, by changing the shape or angle of each microstructure.

[0005] However, even if the structures described in CH711561A1 and CH711562A1 are applied to a light-emitting device, such as a luminaire, to provide a certain degree of glare control, there is a need to better control the glare beam so that a more glare-free luminous flux, and therefore a highly effective luminous flux, can be provided to the luminaire and the occupants of the illuminated space are not disturbed by the glare beam. The Unified Glare Rating (UGR) is used to evaluate discomfort glare. When measuring the UGR value, all lighting within the system that contributes to the glare impression is taken into account. The UGR limit value is specific to each task performed in the illuminated room (e.g., technical drawing, reading, or general industrial work). Because the glare beam can lead to a decrease in concentration and fatigue in people who are sensitive to the glare, controlling the glare beam and adhering to the UGR limit value is very important. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] CH711561A1 [Patent Document 2] CH711562A1 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to improve the glare control of known glare control structures and provide a more glare-free light beam. Therefore, the object is to better control light rays exiting state-of-the-art structures that have propagation angles that result in glare, thereby reducing glare and increasing the effective light beam. In particular, the occupants of the illuminated space are not disturbed by the glare beam.

[0008] overview The main objective has been solved by the subject matter of the present application and its preferred embodiments disclosed herein. [Means for solving the problem]

[0009] A first subject of the invention comprises a layer L1 and a layer L2, a) layer L1 is made of a transparent material and has at least one surface with a microstructure that provides layer L1 with glare control properties; and b) layer L2 is made of one or more transparent materials that provide layer L2 with anti-reflection properties; a layer L2 on the surface of the layer L1 having the microstructure; It is a transparent multilayer system.

[0010] The transparent multilayer system described above is referred to herein as "transparent multilayer system according to the invention" or "multilayer system according to the invention".

[0011] The present invention further provides, as a second subject matter, a method for producing a medicament comprising the steps of: i. forming a layer L1 comprising a microstructure on at least one surface, preferably on one surface, followed by ii. Below a. depositing one or more coating materials onto the surface of the microstructured layer L1 to form an anti-reflective coating layer L2; or b. Partially removing material from the surface of the layer L1 having the microstructure, thereby preserving the shape of the microstructure, to form an anti-reflection layer L2 from the same material as layer L1. forming an anti-reflection layer L2 by a method for producing a transparent multilayer system according to the present invention, comprising:

[0012] Another subject of the invention is a transparent multilayer system obtainable according to the method of the invention.

[0013] A fourth subject of the present invention is the use of a transparent multilayer system according to the invention as a glare control component in a light-emitting device, such as a luminaire, which component is intended to be between a light source and a person exposed to the light transmitted through the component.

[0014] A further subject of the invention is a luminaire comprising a light source and a transparent multilayer system according to the invention. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows anti-reflection (AR), anti-glare (AG), and glare control (GC) and the resulting glare of the beam. [Figure 2] 2A-2C show a multilayer system of the present invention. [Figure 3] 3A-3C show a multilayer system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Detailed Description definition The term "transparent" denotes the transmission of visible light through a transparent medium, for example the material from which the multilayer system according to the invention is composed.

[0017] A "transparent medium" is a medium that transmits visible light without causing substantial significant scattering. This contrasts with opaque or non-transparent media, such as milk glass or translucent glass, which transmit visible light but are not transparent and are "milky." In the present invention, the degree of light transmission through each layer material of a multilayer system should preferably be observed to be greater than 80%. Light transmission is measured using ASTM D-1003 (Standard Test Method for Haze and Light Transmission of Transparent Plastics).

[0018] The term "anti-reflective" (commonly abbreviated as AR) refers to a type of coating or treatment applied to optical surfaces, such as lenses or screens, to reduce or eliminate light reflection at the interface between the surface and the surrounding medium. Anti-reflective coatings work by utilizing the principle of interference in multiple thin layers of different refractive indexes applied to the surface or by creating a gradient in refractive index between the medium and the surface. This gradient helps reduce abrupt changes in refractive index, minimizing the light reflection perceived by the observer compared to a typical transparent substrate (Figure 1B). By reducing reflection, anti-reflective coatings improve the clarity, contrast, and brightness of transmitted or reflected light. Anti-reflective coatings are commonly used in a variety of optical applications, including eyeglasses, camera lenses, microscopes, telescopes, solar panels, and display screens. Various materials, such as magnesium fluoride or titanium dioxide, can be used to create anti-reflective coatings, and the number and thickness of layers can be optimized for specific wavelengths or ranges of light.

[0019] The term "anti-glare" (commonly abbreviated as AG) refers to a type of optical layer or interface, such as a screen or lens, that reduces or eliminates reflections or glare caused by ambient or direct light sources. Anti-glare coatings work by diffusing or scattering light from external sources that strike the surface, rather than reflecting it back to the viewer (Figure 1C). This results in a clearer, more comfortable image and reduces eye strain and visual fatigue. Anti-glare coatings are commonly used on computer monitors, smartphones, televisions, eyeglasses, camera lenses, and other optical devices. Anti-glare layers can be layers containing microstructures with many different tilt angles relative to the surface, such as randomized structures or scattering centers, or can be made from a variety of materials, such as silica, titanium dioxide, or polyurethane, and can be applied using a variety of methods, such as vacuum deposition, spray coating, or lamination.

[0020] On the other hand, the term "glare control" as used herein refers to the ability of an optical layer or interface to reduce or eliminate the harsh, unpleasant, and potentially dangerous effects of excessive brightness or glare transmitted through its surface from a light source, such as artificial lighting. That is, compared to "anti-glare," the observer is faced with a beam that passes through the optical layer or interface rather than being diffusely reflected from the optical layer or interface. In glare control, the observer and the light source are on opposite sides of such an optical layer or interface. Glare control works by altering the ray path of light passing through an optical layer or interface so that a light beam incident on one side of the optical layer or interface emerges on the opposite side at a lower angle (relative to the surface normal of the substrate, respectively) than the light beam that entered the optical layer or interface ( FIG. 1F ).

[0021] 1A-1H further elucidate the difference between anti-reflection (AR), anti-glare (AG), and glare control (GC) structures used herein, and the combination of anti-reflection (AR) and anti-glare (AG) layers known from the literature, and the combination of anti-reflection (AR) and glare control (GC) layers disclosed herein by the present invention, resulting in further reduction or elimination of surprising glare as a result of a beam transmitted through the glare control (GC) structure.

[0022] FIG. 1A is a schematic diagram of a beam of light incident on a plane-parallel transparent substrate. The incident beam is partially specularly reflected and partially transmitted. Partial reflection at a second interface between the material and air is omitted for clarity of illustration. FIG. 1B is a schematic diagram of a beam of light incident on a plane-parallel transparent substrate with an anti-reflection layer on the side of the substrate facing the light source. The incident beam is partially specularly reflected and partially transmitted. This greatly reduces the reflection reaching the observer, ideally close to zero percent.

[0023] Figure 1C is a schematic diagram of a beam incident on a plane-parallel transparent substrate with anti-glare structures on the side of the substrate facing the light source. The incident beam is partially reflected and partially transmitted, resulting in a similar amount of reflection as with the transparent substrate (Figure 1A). The reflection is therefore diffuse, not specular. That is, a bundle of light rays incident on the surface from one direction is reflected in multiple directions. Therefore, the anti-glare layer can be a layer containing microstructures with many different tilt angles relative to the surface, such as randomized structures or scattering centers.

[0024] FIG. 1D is a schematic diagram of a beam incident on a plane-parallel transparent substrate with an anti-glare structure and an anti-reflection layer on the side of the substrate facing the light source. The incident beam is partially reflected and partially transmitted, with the anti-reflection layer significantly reducing the amount of reflection and the anti-glare layer diffusively spreading this significantly reduced amount of reflection. In this way, the combination of the anti-reflection and anti-glare layers can further suppress glare due to reflected light on the same side of the substrate as the light source. Exemplary patent applications related to "anti-glare" and anti-reflection can be found, for example, in JP2022015702A1 and US2015 / 0226882A1.

[0025] Figure 1E is a schematic diagram of a beam incident on and transmitted through a plane-parallel transparent substrate. The incident and transmitted beams have the same propagation direction. Therefore, a beam at a high angle of incidence relative to the surface normal continues to propagate at that high angle after leaving the substrate. In a lighting fixture, for example, such high-angle light rays increase the glare perceived by the observer.

[0026] FIG. 1F is a schematic diagram of a beam from a light source incident on and transmitted through a transparent substrate having a glare control feature on the opposite surface. The glare control structure changes the angle of the transmitted beam so that the incident and transmitted beams do not have the same propagation direction. The transmitted beam propagates at a lower angle relative to the surface normal of the substrate than the incident beam, thereby reducing the glare perceived by the viewer. Exemplary patent applications relating to "glare control" can be found, for example, in CH711561A1 and CH711562A1.

[0027] FIG. 1G corresponds to the setup of FIG. 1F and further shows partial reflection of the incident beam at the interface between the glare control structure and air, this partially reflected beam exiting the glare control structure after an intermediate reflection on the incident side of the substrate at a higher, and therefore more detrimental in terms of glare, angle relative to the surface normal.

[0028] 1H is a schematic diagram of the present invention, in which a beam is incident on and transmitted through a transparent substrate that has glare control features and an anti-reflective (AR) layer on the surface opposite from the light source. The anti-reflective layer significantly reduces (ideally to zero percent) the partial reflection at the interface between the glare control features and air, thereby reducing the amount of glare after intermediate internal reflections.

[0029] Transparent multilayer system The transparent multilayer system of the present invention comprises or consists of a layer L1 and a layer L2, where layer L1 is made of a transparent material and has at least one surface with a microstructure that provides layer L1 with glare control properties, and antireflective layer L2 is made of one or more transparent materials that provide layer L2 with antireflective properties, layer L2 being on the surface of layer L1.

[0030] Hereinafter, the layer L1 will also be referred to as the "glare control layer L1" or simply as the "glare control layer", and the layer L2 will also be referred to as the "antireflection layer L2" or simply as the "antireflection layer".

[0031] In the context of the present invention, the anti-reflection layer L2 improves the glare control properties of layer L1, and thus the transparent multilayer system of the present invention provides improved glare control properties.

[0032] The inventors of the present invention have found that the combination of a first layer having glare control properties and a second layer having anti-reflective properties leads to improved glare control.

[0033] Both types of layers L1 and L2 have already been found in the state of the art and described in the prior art. However, the combination of both types of layers to improve glare control has not yet been envisaged. In the following, both the layers and the methods for their manufacture will be described in more detail.

[0034] Layer L1 Layer L1 is provided with at least one surface, preferably one surface, with a microstructure that provides layer L1 with a certain degree of glare control properties, for example as described in CH711561A1 or CH711562A1.

[0035] Microstructure shape, size and pattern of the microstructure Like all layers, layer L1 has two surfaces, at least one of which, preferably one, has a microstructure. The microstructure typically forms a pattern, preferably a regular pattern, which is responsible for the glare control properties of layer L1. Preferably, one surface of layer L1 has a microstructure, and the other surface is a smooth surface (i.e., a flat surface without a microstructure). In the use method according to the present invention described below, the smooth side is typically the side facing the light source.

[0036] The microstructures preferably have a height in the range of 5 μm to 5000 μm, more preferably 5 μm to 1000 μm, even more preferably 5 μm to 500 μm or 5 to 300 μm, even more preferably 5 to 150 μm, for example, 30 to 120 μm or 30 to 100 μm. The "height of the microstructure" is the height of the elevation starting from the lowest point between the elevations. However, the height can vary significantly while still observing the glare control properties. However, within the same layer L1, it is preferred that the height of each microstructure is approximately the same to obtain a uniform impression.

[0037] The microstructures can have various shapes. For example, the microstructures can have the shape of a cone, a pyramid, or a prism. A microstructure with a pyramid shape can have a triangular or square base, and the pyramid can also be an inverted pyramid with a triangular or square base. Other possible microstructures are prisms, Fresnel lens-like structures, microlens-like structures with a hexagonal or square lattice arrangement, or a combination of two linear structures of a prism.

[0038] Preferably, the microstructure has a hexagonal, square or other lattice configuration, most preferably a hexagonal lattice configuration.

[0039] Preferably, the microstructures have a conical shape, more preferably cones with a hexagonal lattice arrangement. Preferably, the cones have an apex angle of 90° to 130°, more preferably 100° to 120°, even more preferably 105° to 115°, and most preferably 110°.

[0040] Preferably, the microstructure has a base with a maximum diameter of 5 μm to 1000 μm, more preferably 50 μm to 500 μm, and most preferably 150 μm to 350 μm. Preferably, the microstructure has a base angle in the range of 10° to 60°, more preferably 20° to 55°, the base angle being the inclination angle of the microstructure.

[0041] Materials used to form layer L1 The material forming layer L1 preferably has a refraction index n1 measured at a wavelength of 589 nm in the range of 1.35 to 2.00, more preferably 1.40 to 1.85, and most preferably 1.45 to 1.75. As used herein, the term "refractive index" refers to the ratio of the speed of light in a vacuum to the speed of light in a given medium at a wavelength of 589 nm.

[0042] Preferably, layer L1 is formed from glass or a polymeric material or a blend of polymeric materials or a blend of polymeric and inorganic materials. The term "polymer" refers to a material composed of several monomers with different degrees of polymerization, molar masses and chain lengths. The monomers may be the same or different. A polymeric material is made from or contains a polymeric substance as the main component. The term therefore also includes a cured coating material, preferably obtained from a liquid coating composition, that has cured before layer L2 is applied.

[0043] Optical glasses have refractive indices ranging from approximately 1.46 (fused silica) to 1.85 (lanthanum heavy flint glass) at a wavelength of 589 nm.

[0044] The polymeric material may be thermoplastic or thermosetting, and is preferably a thermosetting material, and may be in the form of a plastic foil, a plastic sheet, or a cured coating obtained from the curable coating composition C1.

[0045] Typical polymeric materials, such as plastic foils and sheets, preferably consist of or comprise polyolefins such as polyethylene or polypropylene, polyvinyl chloride, celluloid, polystyrene, polyetheretherketone, polyamide, acrylonitrile butadiene styrene, polylactide (PL), polymethyl methacrylate (PMMA), polycarbonate, polyethylene terephthalate (PET), epoxy, polyurethane, polyurethane-acrylate, polyurea, poly(ethylene-propylene), polydiorganosiloxane, polybutadiene, polychloroprene, chlorinated polyethylene and fluorosilicone, fluorinated polyurethane, perfluoropolyether, and / or blends thereof. The most preferred plastic materials are polycarbonate, PMMA, and PET, with polycarbonate being the most preferred.

[0046] Preferably, the layer L1 containing the microstructure is a plastic foil or sheet, as known from, for example, CH711561A1 or CH711562A1. The plastic foil according to the present invention relates to a relatively large and thin structure. The structure typically has a much larger area relative to its thickness. For example, such a structure can have a thickness of less than 1 mm, typically less than 0.5 mm, while the surface can be any size. The plastic sheet can be thicker, for example, 1 mm or more, but can be made of the same material as the plastic foil.

[0047] The plastic foil or sheet preferably has a refractive index n1 of 1.35 to 1.65, more preferably 1.40 to 1.60, measured using a wavelength of 589 nm. Preferably, the plastic foil or sheet is made from polycarbonate (n1=1.59), polyethylene (n1=1.50), polymethyl methacrylate (n1=1.49), most preferably polycarbonate.

[0048] In addition to the typical materials mentioned above, such as glass or polymeric materials, it is also possible to form layer L1 by coating techniques, so that a cured coating obtained from curable coating composition C1 can also be used to produce a thermosetting polymeric material.

[0049] Among the curable coating compositions C1, UV-curable coating compositions are preferred. The term "UV-curable coating composition" according to the present invention should be understood to refer to a coating composition that can be partially or completely cured under the influence of ultraviolet radiation. Such UV-curable coating compositions preferably comprise a UV-curable resin, a UV-curable reactive monomer (i.e., a UV-curable reactive diluent), a photopolymerization initiator, a light stabilizer, and / or further coating additives.

[0050] Preferred UV-curable resins are, for example, selected from the group consisting of polyester (meth)acrylates, epoxy (meth)acrylates, aliphatic and / or aromatic urethane (meth)acrylates, preferably aliphatic urethane (meth)acrylates, polyether (meth)acrylates, and (meth)acrylated poly(meth)acrylates. The terms "(meth)acrylic" or "(meth)acrylate" include acrylic and methacrylic or both, and acrylate and methacrylate or both, respectively.

[0051] Suitable UV-curable reactive diluents preferably contain one or more free-radically polymerizable groups, such as vinyl, allyl, or (meth)acrylic groups, more preferably (meth)acrylic groups. Examples of suitable reactive diluents are mono(meth)acrylate-functional monomers, di(meth)acrylate-functional monomers, and tri- and / or tetra(meth)acrylate-functional monomers. Preferred mono(meth)acrylate-functional monomers are hydrocarbyl esters of (meth)acrylic acid, where the hydrocarbyl residue may be aliphatic or aromatic, and linear, branched, or cyclic. Preferably, the hydrocarbyl group contains 1 to 20, more preferably 4 to 18, carbon atoms, and the hydrocarbyl group may contain one or more ether oxygens. Preferred di(meth)acrylate functional monomers are alkanediol di(meth)acrylates (the alkanediol preferably contains 2 to 16, more preferably 3 to 14 carbon atoms), dialkylene glycol di(meth)acrylates, trialkylene glycol di(meth)acrylates, and neopentyl glycol-propoxy di(meth)acrylate, tri(meth)acrylate functional monomers of trimethylolpropane, trimethylolethane or glycerol, and tetra(meth)acrylate functional monomers such as pentaerythritol tetra(meth)acrylate.

[0052] The total amount of the UV-curable resin and the UV-curable reactive diluent is preferably in the range of 80% by mass to 99% by mass, more preferably 85% by mass to 98% by mass, and most preferably 90% by mass to 97% by mass, based on the total mass of the coating composition C1.

[0053] A photoinitiator is used to initiate crosslinking between any vinyl, acrylate, or methacrylate groups within the coating composition. The photoinitiator generates free radicals upon irradiation with UV light, thereby enabling curing using UV light. Such photoinitiators are preferably selected from the group consisting of alpha-cleavable photoinitiators, such as alpha-hydroxyketones (e.g., benzoin, acetophenone), alpha-alkoxyketones (e.g., benzoin ethers, benzil ketals), alpha-aminoketones, and acylphosphine oxides. The UV photoinitiator is preferably present in Coating Composition C1 in an amount of 0.5% to 6% by weight, most preferably 0.75% to 5% by weight, and even more preferably 1% to 3% by weight, based on the total weight of Coating Composition C1.

[0054] Coating composition C1 may further comprise a UV absorber, preferably selected from the group consisting of 2-(2'-hydroxyphenyl)benzotriazole, 2-hydroxybenzophenone, esters of substituted and unsubstituted benzoic acid, acrylates such as ethyl alpha-cyano-beta,beta-diphenylacrylate, 2-(2-hydroxyphenyl)-1,3,5-triazine, and oxamide. The amount of UV absorber is preferably in the range of 0 to 8% by weight, more preferably 0.4 to 4% by weight, and most preferably 0.6 to 3% by weight, based on the total weight of coating composition C1.

[0055] The coating composition C1 of the present invention may contain a light stabilizer, such as a hindered amine light stabilizer (HALS), including NOR-HALS. NOR-HALS is a subclass of HALS, also known as aminoxyl radical hindered amine light stabilizers. HALS act as bases and are neutralized by acids, such as hydrochloric acid, but NOR-HALS are not strong bases and are not deactivated by hydrochloric acid. The amount of the light stabilizer is preferably in the range of 0% to 8% by weight, more preferably 0.4 to 4% by weight, and most preferably 0.6 to 3% by weight, based on the total weight of the coating composition C1.

[0056] Coating composition C1 may also contain typical coating additives, such as adhesion promoters, leveling agents, antioxidants, and antifoaming agents, such as (meth)acrylic trialkoxysilanes, (meth)acrylic dialkoxyalkylsilanes, glycidyl group-containing trialkoxysilanes, glycidyl group-containing dialkoxyalkylsilanes, and (meth)acrylated phosphate esters, all of which are preferably, but not necessarily, reactive in UV curing. The amount of coating additives is preferably in the range of 0 to 7 wt %, more preferably 0 to 5 wt %, and most preferably 0 to 3 wt %, based on the total weight of coating composition C1.

[0057] Although not excluded, it is less preferred that coating composition C1 comprises an organic solvent, which, in contrast to a UV-curable reactive diluent, does not chemically react with any of the other compounds of the coating composition upon UV curing, i.e., such a chemically unreactive organic solvent in the sense of the present invention is a single liquid or a blend of liquids that is volatile under certain conditions of use and is added to the coating composition to reduce the viscosity or influence other properties without causing any adverse effects. Preferably, however, coating composition C1 does not contain said chemically unreactive organic solvent.

[0058] The UV-cured layer L1 formed from the above-described UV-curable coating composition C1 can be obtained from a wide range of UV-curable components contained in the UV-curable coating composition C1, and realizes a wide range of refractive index n1.

[0059] The inventors have surprisingly found that a new approach of coating the glare control structure layer L1 with an anti-reflection layer L2 can provide better control of the glare beam.

[0060] Layer L2 An anti-reflective coating layer L2 is formed on layer L1, with the microstructure comprising the surface of L1 facing layer L2. Alternatively, as claimed and described herein below, layer L2 can be formed by removing material from the surface of layer L1. In such cases, layer L2 is typically of the same material as layer L1.

[0061] Typically, the refractive index n2 of layer L2 is lower than the refractive index n1 of layer L1, and therefore the materials used to form layer L2 and / or the manufacturing techniques used to form layer L2 are selected so that n1>n2. For example, if layer L2 is a single homogeneous layer, the refractive indices of the materials used are typically selected so that n1>n2. On the other hand, it is also possible to use, for example, porous or nanostructured surfaces, which lower the overall refractive index of this layer L2, for example by "entrapping" air.

[0062] Generally, the dry layer thickness d of layer L2 L is typically in the submicron range, preferably less than 700 nm, for example in the range of 10 to 700 nm, preferably 50 to 650 nm, even more preferably 80 to 600 nm, depending on the structure, surface and material of the antireflection layer L2.

[0063] Therefore, the dry layer thickness of layer L2 is d L is typically much smaller than the height of the microstructure of layer L1, thereby ensuring that the microstructure of layer L1 is inherited by layer L2, i.e., valleys between the microstructure of layer L1 remain and are not "filled up" by layer L2.

[0064] In fact, any known anti-reflective layer L2 can be formed on the microstructured surface of layer L1, as long as the layer is transparent and meets some requirements from the viewpoint of layer L1 that make this layer L2 anti-reflective. Thus, the term "anti-reflective" already includes information such as the appropriate layer thickness of layer L2, or its refractive index n2, considering that the refractive index of layer L1 is n1.

[0065] Therefore, all necessary information regarding the term "antireflective" considering the properties of layer L2 is already included when it is considered to be antireflective.

[0066] Furthermore, because the concept of the present invention is based on applying an anti-reflective layer L2 on layer L1, as defined above, a proof-of-concept performed with a particular anti-reflective layer L2 can be easily transferred to another anti-reflective layer L2, which is a major advantage of the teachings disclosed herein. Unlike concepts that modify the glare control layer itself with differently shaped microstructures, which can lead to unpredictable results, the present invention can be easily adapted to any kind of anti-reflective layer L2 and is therefore universally applicable.

[0067] The antireflective layer L2 can be of various types and can be broadly classified into the groups of antireflective coating structures and antireflective coating surfaces, although these groups are not necessarily mutually exclusive. For a detailed description of the aforementioned antireflective coating structures and antireflective coating surfaces, as well as techniques relating to methods for manufacturing such antireflective layers, see N. Shanmugam, R. Pugazhendhi, R. Madurai Elavarasan, P. Kasiviswanathan and N. Das, "Anti-Reflective Coating Materials: A Holistic Review from PV Perspective," Energies 2020, 13, 2631 et seq., which are incorporated herein by reference and whose teachings are briefly summarized below.

[0068] Various suitable anti-reflective coating structures are described below.

[0069] i. Single Layer Anti-Reflection Coating (SLARC) SLARC is the simplest form of anti-reflective coating. In this case, Fresnel reflection losses are reduced by applying a single layer film over glare control layer L1, thus creating anti-reflective layer L2. To achieve the anti-reflective properties of SLARC, the refractive index n2 of the material forming layer L2 must be lower than the refractive index n1 of layer L1. The optimal zero reflectance of SLARC in a multilayer coating according to the present invention is achieved when the coating thickness is equal to one-quarter the wavelength of the incident light. To approximate this case, the refractive index n2 of the material of SLARC layer L2 is approximately (n1). -0.5 where n1 is the refractive index of the material forming layer L1.

[0070] As an example, if layer L1 is made from glass having a refractive index n1 of 1.5, the material forming the SLARC layer should optimally have a refractive index n2 of 1.22 at a quarter wave thickness.

[0071] Typically, solid materials with such low refractive indices are rarely available. However, magnesium fluoride (MgF2), with a refractive index of 1.38, is a commonly used material for producing such coatings. Considering the above equation, the optimal refractive index for the material forming layer L1 is a high-index glass with a refractive index of approximately n = 1.90 at a layer thickness of 1 / 4 wavelength for layer L2. In addition to MgF2, other materials, such as SiO2, are commonly used for producing SLARC layers.

[0072] Suitable organic materials for forming layer L2 have a low refractive index of n=1.30 and often belong to the group of fluoropolymers.

[0073] Selected layer thickness d L As mentioned above, the thickness of the layer d depends on the light source, particularly the color of the light. When considering white light, a person skilled in the art would understand that such light contains all wavelengths from about 380 to about 700. Therefore, for most white light emitting sources, the thickness of the layer d L d L=λ / 4, where λ=380 to 700 nm. L The wavelength is about 95 nm to about 175 nm. Glare caused by light with wavelengths close to UV light (wavelengths less than 380 nm) should be particularly avoided. L is preferably selected from the lower end of the range of 85 to 175 nm. L is in the range of 85 to 140 nm, more preferably in the range of 90 to 120 nm, and most preferably in the range of 95 to 110 nm. L The aforementioned values ​​of are particularly suitable when MgF2 is selected as the layer material for the SLARC.

[0074] ii. Dual Layer Anti-Reflection Coating (DLARC) DLARC consists of two layers (referred to herein as L 2.1 and L 2.2 ), both of which together form the layer L2, and the layers may have the same or different thicknesses. When the film thicknesses are equal, the optimum condition for zero reflection is given by the following equation (n 2.1 / n 2.2 )=(n air / n1) 0.5 where n air = refractive index of air, n1 = refractive index of the material of layer L1, and n 2.1 and n 2.2 = layer L 2.1 and L 2.2 is the refractive index of the layer L 2.1 is the layer in direct contact with layer L1. In general, when a typical DLARC is used, the effective reflectance decreases significantly at the target wavelength, approaches zero, and then gradually increases, resulting in a V-shaped reflectance curve over the analyzed spectral range.

[0075] iii. Multi-layer anti-reflective coating (MLARC) MLARC uses more than two layers to form the entire layer L2. MLARC can avoid the gradual increase in reflectance typically observed with DLARC. As an example, the reflectance of a MgF2 / ZnS DLARC is 9.1% and 0.58% at 500 nm and 1000 nm, while the reflectance of a MgF2 / Al2O3 / ZnS MLARC (3 layers) is 5.8% and 0.88% at 500 nm and 1000 nm, respectively. This demonstrates the broader range of low reflectance for multilayer coatings.

[0076] iv. Gradient Refractive Index Coating (GRINC) A series of layers with a stepwise change in refractive index constitutes a gradient refractive index coating. Alternatively, a non-uniform film with a monotonically varying refractive index is preferred, which functions as a broadband antireflection coating. Various GRINC profiles have been proposed for omnidirectional and broadband antireflection coatings, including linear, parabolic, cubic, Gaussian, quintic, exponential, exponential-sine, and Klopfenstein. Linear refractive index profiles can be easily realized on silicon or quartz substrates. A refractive index gradient can be achieved by varying the packing density of the layers, but this may affect the mechanical robustness and durability of the layer.

[0077] Various suitable anti-reflective coating surfaces are described below.

[0078] v. porous layer Porous layers, especially nanoporous layers, can also function as antireflection coatings. It is essential that the pore size of these layers be much smaller than the wavelength of the incident light. The refractive index of such nanoporous materials is averaged over the layer L2. Porous layers L2 can be in the form of, for example, SLARC and GRINC structures, and are fabricated by chemical etching processes followed by heat treatment. Another approach, as described by Walheim, S.; Walheim, S.; Schaffer, E.; Mlynek, J.; and Steiner, U. in "Nanophase-Separated Polymer Films as High-Performance Antireflection Coatings" in Science 1999, 283, 520-522, has been to obtain high-performance broadband antireflection coatings by precisely varying the volume fraction of nanophase-separated polymer films. The latter technique allowed for refractive indices n2 ranging from 1.2 to 1.05 and transmittances as high as 99.7% in the visible wavelength range.

[0079] vi. Biomimetic Photonic Nanostructures This type of layer L2 is based on subwavelength structures (SWS). Periodic arrays of SWS that function as antireflection surfaces were first discovered by Bernhard in 1967 in the eyes of nocturnal moths. The antireflection structure of a moth's eye consists of an outer surface with a submicron height and an array of spaced nipples. Thus, the refractive index gradually changes between air and the substrate, actively suppressing reflections at the interface between the two media. The reflectivity of such a structure depends on the spacing between the arrays, the effective height of the nanostructures, and the wavelength. In the ideal case, broadband antireflection properties can be obtained by adjusting the spacing as finely as possible and increasing the height. Three models have been proposed to reproduce the nipple structure: conical, parabolic, and Gaussian bell. It has been reported that parabolic nipples exhibit excellent antireflection performance at normal incidence. It has also been reported that the reflectivity decreases significantly for nipples with a larger overlap width at the base, and gradually decreases with increasing height. Monolayer films with gradient refractive index and moth-eye patterns are known, inter alia, from Han et al., Biosurface and Biotribology 2 (2016) 137-150 or Choi et al., Polymers (2020), 12,296.

[0080] Such nanostructures preferably have a height of 10 nm to 500 nm, more preferably 20 nm to 400 nm, even more preferably 50 nm to 300 nm, even more preferably 100 nm to 300 nm, and most preferably 300 nm. The diameter of the nanostructures is preferably 10 nm to 500 nm, more preferably 20 nm to 300 nm, and most preferably 50 nm to 100 nm.

[0081] vii. Textured Surfaces Surfaces with texture periods smaller than the target wavelength and heights of fractions of the wavelength are also suitable for anti-reflection applications. In theory, when the wavelength of light is much larger than the spacing between structures, the textured surface can be treated as a layer with a graded refractive index, and the optical properties can be predicted using the effective medium approximation. When the wavelength of light is shorter than the period between the textured structures, the light rays undergo multiple reflections and become trapped in the gaps. In this case, the optical properties are defined by geometry alone, and numerical modeling is performed using ray tracing.

[0082] Material used to form layer L2 Depending on the type of anti-reflective coating structure and / or surface, several different materials can be applied, deposited by different techniques. Below, various types of suitable materials and their application techniques are disclosed.

[0083] The anti-reflective coating material is preferably from the following group of materials: a. silicon-based coating materials (including, for example, silicon oxide and silicon-based nanomaterials); b. metal-based coating materials (including, for example, metal oxides and metal fluorides); c. polymer-based coating materials (e.g., polystyrene, polymethyl methacrylate, polydimethylsiloxane, and polyethylene terephthalate), and d. Composite coating materials It is classified as follows.

[0084] a. Silicon-based anti-reflective coating materials Silicon-based coating materials are often and preferably based on silicon dioxide (ie, silica) coating materials.

[0085] The single silica layer can be formed, for example, as a nanoporous layer, by sol-gel dip coating, as described, for example, in Mahadik, DB; Lakshmi, RV; Barshilia, HC, "High performance single layer nano-porous antireflection coatings on glass by sol-gel process for solar energy applications", Sol. Energy Mater. Sol. Cells 2015, 140, 61-68, or by chemical etching and thermal oxidation, as described, for example, in Cao, H.; Bai, Y.; Qiao, L, "Antireflection effect of SiO2 thin film on the pyramidal textured surface of monocrystalline silicon", Opt. Int. J. Light Electron Opt. 2015, 126, 2643-2645.

[0086] Bilayer porous silica films with an extremely low refractive index of about 1.11 can be obtained, for example, by plasma-enhanced chemical vapor deposition, as described, for example, in Nagel, H.; Metz, A.; Hezel, R., "Porous SiO2 films prepared by remote plasma-enhanced chemical vapor deposition—a novel antireflection coating technology for photovoltaic modules," Sol. Energy Mater. Sol. Cells 2001, 65, 71-77.

[0087] Multilayer stacks of silica obtained by sol-gel evaporation-induced self-assembly techniques are described by Agustin-Saenz, C.; Sanchez-Garcia, J.A.; Machado, M.; Brizuela, M.; Zubillaga, O.; Tercjak, A. in "Broadband antireflective coating stack based on mesoporous silica by acid-catalyzed sol-gel method for concentrated photovoltaic application," Sol. Energy Mater. Sol. Cells 2018, 186, 154-164.

[0088] Four-layer nanoporous silica structures exhibiting negligible reflection obtained by glancing angle deposition technique have been obtained as described in "Nanostructured porous SiO2 films for antireflection coatings" by Sobahan, KMA; Park, YJ; Kim, JJ; Hwangbo, CK, Opt. Commun. 2011, 284, 873-876, and five-layer structures with hollow silica nanoparticles obtained by dip coating have been disclosed in "Preparation and properties of five-layer graded-refractive-index antireflection coating nanostructured by solid and hollow silica particles" by Jia, G.; Ji, Z.; Wang, H.; Chen, R., Thin Solid Film 2017, 642, 174-181.

[0089] More sophisticated, yet still cost-effective and accessible, structures such as nanocylinders can be fabricated by sol-gel and soft imprint lithography as described in Van de Groep, J.; Spinelli, P.; Polman, A., "Single-Step Soft-Imprinted Large-Area Nanopatterned Antireflection Coating," Nano Lett. 2015, 15, 4223-4228.

[0090] Silica-based moth-eye-like structures can be obtained, for example, by sol-gel dip-coating and electrostatic self-assembly techniques, as described in Li, D.; Han, S.; Li, A.; Wang, Y.; Shan, Y.; Huang, F., "Novel-type nanostructured SiO2 antireflection coatings and their application in Cu(In,Ga)Se2 solar cells," Mater. Chem. Phys. 2015, 165, 97-102.

[0091] b. Metal-based anti-reflective coating materials Metal oxides commonly used in anti-reflective coating materials are titanium dioxide, indium-tin oxide (ITO), aluminum oxide, tantalum oxide and zinc oxide, while the most important metal fluoride is magnesium difluoride.

[0092] Titanium dioxide thin films can be produced, for example, by liquid phase deposition, as described in Huang, J.-J.; Lin, C.-C.; Wuu, D.-S., "Antireflection and passivation property of titanium oxide thin film on silicon nanowire by liquid phase deposition," Surf. Coat. Technol. 2017, 320, 252-258.

[0093] Zinc oxide thin films can be obtained by a sol-gel method as described in Makableh, YF; Vasan, R.; Sarker, JC; Nusir, AI; Seal, S.; Manasreh, MO, "Enhancement of GaAs solar cell performance by using a ZnO sol-gel anti-reflection coating. Sol. Energy Mater. Sol. Cells 2014, 123, 178-182."

[0094] Moth-eye structures from zinc oxide were described by Shin, B.-K.; Lee, T.-I.; Xiong, J.; Hwang, C.; Noh, G.; Cho, J.-H.; Myoung, J.-M., "Bottom-up grown ZnO nanorods for an antireflective moth-eye structure on CuInGaSe2 solar cells." Sol. Energy Mater. Sol. Cells 2011, 95, 2650-2654.

[0095] MgF2 coating forms a mesoporous nanoparticle layer, for example, by lyothermal and dip coating processes, as described by Pendse, S.; Chandra Sekhar Reddy, K.; Narendra, C.; Murugan, K.; Sakthivel, S., "Dual-functional broadband antireflective and hydrophobic films for solar and optical applications," Sol. Energy 2018, 163, 425-433.

[0096] c. Polymer-based anti-reflective coating materials In polystyrene (PS), biomimetic nanopillar and pyramid array films can be fabricated using microinjection compression molding techniques, as described, for example, in Xie, H.; Huang, H.-X.; Peng, Y.-J., "Rapid fabrication of bio-inspired nanostructures with hydrophobicity and antireflectivity on polystyrene surfaces replicating from cicada wings," Nanoscale 2017, 9, 11951-11958, and Peng, Y.-J.; Huang, H.-X.; Xie, H., "Rapid fabrication of antireflective pyramid structures on polystyrene films used as protective layers of solar cells," Sol. Energy Mater. Sol. Cells 2017, 171, 98-105.

[0097] Polymethyl methacrylate (PMMA) coatings with nanocone arrays can be fabricated as described by Choi, K.; Park, SH; Song, YM; Lee, YT; Hwangbo, CK; Yang, H.; Lee, HS, "Nano-tailoring the Surface Structure for the Monolithic High-Performance Antireflection Polymer Film," Adv. Mater. 2010, 22, 3713-3718, and simple, large-scale nanopatterns can be cost-effectively fabricated using thermal nanoimprinting, laser lithography, and dry etching as shown in Kim, S.; Jung, UT; Kim, S.-K.; Lee, J.-H.; Choi, HS; Kim, C.-S.; Jeong, MY, "Nanostructured Multifunctional Surface with Antireflective and Antimicrobial Characteristics," ACS Appl. Mater. Interfaces 2015, 7, 326-331.

[0098] Other approaches use polydimethylsiloxane (PDMS) or polyethylene terephthalate (PET) to form nanodomes, poly(methylsilsesquioxane) (PMSSQ) to provide nanoporous films with refractive indices in the low range of 1.44 to 1.18, and others described in Table 5 and subsequent publications in the aforementioned publication by N. Shanmugam et al., Energies 2020, 13, 2631.

[0099] d. Composite coating materials Numerous approaches using combinations of two or more of SiO2, TiO2, Al2O3, ZnO, and MgF2 are described in the aforementioned publication by N. Shanmugam et al., Energy 2020, 13, 2631, Table 6 et seq., and in the underlying scientific publications showing how to produce such coatings.

[0100] Additional layer L S and L A The transparent multilayer system of the present invention may be on one or more additional layers, with the smooth surface of layer L1 facing the one or more additional layers. S This can be, for example, a layer L1 onto which a coating composition C1 can be applied to form a layer L1. S are suitable for supporting the transparent multilayer systems of the present invention.

[0101] Preferably, layer L S is formed from a coating composition comprising a polymer selected from the group consisting of polyolefins, such as polyethylene or polypropylene, polyvinyl chloride, celluloid, polystyrene, polyetheretherketone, polyamide, acrylonitrile butadiene styrene, polylactide, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyetherketoneketone, polyetherketone, polyimide, polyester, chloro- or fluoro-polymers, such as polytetrafluoroethylene, fluorinated ethylene propylene, or fluorinated polyurethane, silicone, epoxy, polysulfide, ethylene propylene diene, fluorosilicone and / or fluoroelastomer.

[0102] Furthermore, layer L1 or layer L2 of the transparent multilayer system of the present invention S additional layer L made of a material that allows the transparent multilayer system of the invention to be attached to the transparent part of the luminaire. A The additional layer L may be formed on the surface to provide an improved glare control structure for the area. A Suitable examples of the adhesive layer include, for example, layers consisting of or comprising adhesive compositions. Such adhesive layers can be attached to the backing layer L, which is peeled off before the transparent multilayer system of the present invention is fixed to the transparent part of the luminaire. B It may be covered with

[0103] Thus, the transparent multilayer system according to the invention comprises a layer L1 and a layer L2, where the layer L2 is a single layer with a constant refractive index n2 (see FIG. 2A) or a layer with a gradient refractive index n 2G (see FIG. 2B), or a multilayer film formed from multiple materials, each layer having a different refractive index, each refractive index being less than the refractive index n1 (see FIG. 2C). For simplicity, the multilayer L2 is shown in FIG. 2C as a two-layer structure consisting of a gray layer and a black layer. However, the multilayer L2 may consist of more than two layers, as outlined herein above. Additional layers L S and / or L A 3A to 3C, the layer L2 is depicted as a single layer for simplicity, as in FIG. 2A. The layer L1 of the transparent multilayer system according to the present invention is connected to the support layer L S (See FIG. 3A). S The transparent multilayer system according to the invention comprises an additional layer L A Furthermore, the transparent multilayer system according to the invention can be formed on the layers L1 and L2 (see FIG. 3B). A Support layer L between S Without additional layer L A (See FIG. 3C).

[0104] Method for producing transparent multilayer systems As mentioned above, the present invention further comprises the steps of: i. forming a layer L1 comprising a microstructure on at least one surface, preferably on one surface, followed by ii. Below a. depositing one or more coating materials onto the surface of the microstructured layer L1 to form an anti-reflective coating layer L2; or b. Partially removing material from the surface of the layer L1 having the microstructure, thereby preserving the shape of the microstructure, to form an anti-reflection layer L2 from the same material as layer L1. forming an anti-reflection layer L2 by a method for producing a transparent multilayer system according to the present invention, comprising:

[0105] Different mandatory layers L1 and L2, and optional layer L s and L A The materials, their physical properties, such as the refractive index or their chemical composition, and also their dimensions, such as the layer thickness, have already been described herein above for the transparent multilayer systems of the present invention, and therefore reference can be made in this respect to the respective passages herein above.

[0106] The term "partially removing material" refers to an etching technique, e.g., an ablation technique such as plasma etching, which tends to remove parts of the surface of layer L1, thereby creating a substructure on this layer and thus creating an antireflective layer L2. "Maintaining the shape of the microstructure" means that the general shape of the microstructure of layer L1 remains, but the surface of such microstructure is substructured to obtain antireflective properties. Such a substructured surface is therefore considered an antireflective layer L2 in the context of the present invention.

[0107] In the following, we will focus on how to obtain such transparent multilayer systems.

[0108] Process i. The above step i. requires the formation of a layer L1 comprising microstructures on at least one of its two surfaces, the microstructures having a height in the range of 5 μm to 100 μm, said layer having a refractive index n1.

[0109] The formation of such microstructures can be achieved by several methods, such as laser ablation, hot stamping, UV casting, injection molding, compression molding, roll-to-roll processes, embossing processes, plasma etching processes, sol-gel processes, and / or 3D printing.

[0110] Hot stamping uses a combination of pressure and heat to form a microstructure in a film or sheet. In this process, the film or sheet is fed into a stamping machine equipped with a stamping head bearing the inverse of the desired microstructure. The heated stamping head is pressed against the film or sheet, imprinting the desired microstructure into the film or sheet to form layer L1. The stamping temperature should be in the range of 100°C to 250°C. This is because this process uses heat to imprint the microstructure on the film or sheet, and the materials used must be able to be formed under heat. Therefore, transparent multilayer systems in which layer L1 is formed from such materials are suitable only for light-emitting sources that do not generate much heat, such as light-emitting diodes. Otherwise, deformation of layer L1 or flattening of the microstructure over time may occur.

[0111] The microstructures can also be formed using an injection or compression process, both of which utilize heat and / or pressure. In this process, a mold with the desired microstructure is used in an injection molding process. Molten polymer material is injected into such a mold. After a cooling process, the mold is opened and a solid layer containing the microstructure is ejected. In the case of compression molding, a thermoplastic material is preferably placed into a hot mold with the desired microstructure. The mold is then closed with a hydraulic press. The heat and pressure form a layer L1 with the microstructure on at least one of its two surfaces.

[0112] Another method of using pressure to generate the desired microstructure on layer L1 is an embossing process, in which an embossing tool having an inverted desired microstructure is used, which is transferred onto at least one of the two surfaces of layer L1 formed from uncured composition C1, forming the microstructure on at least one surface of layer L1.

[0113] The microstructures can be formed on layer L1 using a plasma etching process. For example, Ar / O2SF6, N2, or ClF3 can be used as the etching plasma. The microstructures are formed on the surface of a polymer film or sheet by etching the surface with plasma in a vacuum chamber. This process is known, for example, as AR-plas® and AR-plas2®. Preferably, layer L1 is formed from a polymethyl methacrylate or polycarbonate film or sheet when the microstructures are formed using a plasma etching process.

[0114] Roll-to-roll processes can also be used to create structures on rolled materials or flexible glass. This process begins with a roll of flexible material, which is then coated, printed, or otherwise processed, and then rewound to create an output roll. These processes, along with other steps such as sheeting, can be summarized under the general term converting. Once the roll of material is coated, laminated, or printed with microstructures, it is subsequently cut to size on a slitter / rewinder.

[0115] The microstructure can be formed using ultraviolet (UV) casting, where a UV-curable coating composition is applied to a casting mold that is highly transparent to UV light and exhibits the desired microstructure, and the UV-curable coating composition is understood to refer to a coating composition that can be partially or completely cured under the influence of UV radiation. Curing occurs in the mold by UV radiation, where UV radiation refers to radiation with a wavelength in the range of 100 nm to 380 nm, more preferably 280 nm to 380 nm, and most preferably 315 nm to 380 nm.

[0116] Particularly preferred is roll-to-roll UV nanoimprint lithography.

[0117] Process ii. In the above sections on the structure, surfaces and materials of layer L2, many coating techniques have already been mentioned, which can be categorized as conventional or non-conventional.

[0118] The prior art techniques can be classified into "bottom-up" and "top-down" approaches. The most important of the so-called bottom-up approaches are sol-gel, thermal evaporation, sputtering, oblique angle deposition (GLAD), and chemical vapor deposition (CVD), which are processes according to step ii.a., while the so-called top-down approaches include wet etching and dry etching, which are processes according to step ii.b.

[0119] Non-conventional techniques are in particular lithography, such as photolithography, focused ion beam techniques, and nanoimprint techniques, microreplication, photoaligning and photopatterning.

[0120] All of the above techniques are known and, in principle, suitable for depositing an anti-reflective coating material on the surface of layer L1 to form anti-reflective layer L2. These techniques are described above and are within the knowledge of those skilled in the art. For experimental details, see N. Shanmugam, R. Pugazhendhi, R. Madurai Elavarasan, P. Kasiviswanathan and N. Das, "Anti-Reflective Coating Materials: A Holistic Review from a PV Perspective," Energies 2020, 13, 2631 et seq. (Chapter 5) and the scientific papers cross-referenced therein, which provide detailed descriptions of the manufacturing techniques.

[0121] It will also be apparent to those skilled in the art that techniques that destroy the integrity of layer L1 are excluded. For example, heat-based techniques may be applied to form layer L2 on, for example, glass layer L1, but may not be suitable for thermoplastic layer L1. Alternatively, techniques that use certain non-aqueous solvents in antireflective coating materials to form layer L2 may be problematic when used with certain polymeric materials used to manufacture layer L1 because the solvents may swell or dissolve them. Such undesirable interactions are known to those skilled in the art and can be avoided by using other material combinations for L1 and L2.

[0122] A further subject of the invention is a transparent multilayer system obtainable by the method of the invention.

[0123] How to use transparent multilayer systems The transparent multilayer system according to the present invention is suitable for several applications, preferably as a glare-reducing component of a light-emitting device, such as a lighting fixture. The transparent multilayer system according to the present invention can also be used in any other component in which light should be transmitted with high transmittance but with very low glare. Such additional components are preferably selected from the group consisting of windows, imaging lenses, and solar cells. The transparent multilayer system according to the present invention is preferably intended to cover the light source of a lighting fixture in the direction of light emission of the lighting fixture. The multilayer system is therefore intended to be between the light source and a person who is exposed to light transmitted through the multilayer system or a component containing the multilayer system.

[0124] Lighting fixtures, including transparent multilayer systems The present invention further provides a luminaire comprising a light source and a transparent multilayer system according to the present application. The transparent multilayer system according to the present application covers the light source of the luminaire in the direction of light emission of the luminaire. Typically, the light source of the luminaire is separated from the multilayer system according to the present application by an air gap. Furthermore, the multilayer system may comprise an additional layer L which is adhesive. A The transparent part of the lighting fixture can be attached via the additional layer L. Aand the multilayer system forms a stack. Such a transparent part can be, for example, a rigid substrate such as a polymethyl methacrylate board. Such a stack can be placed facing the light source during or after the manufacture of the luminaire, while still leaving an air gap between the light source and the transparent part. The luminaire can be an indoor or outdoor luminaire, preferably an indoor luminaire. The indoor luminaire can be a ceiling luminaire, a wall luminaire, a floor luminaire, a hanging luminaire, or a table luminaire. [Example]

[0125] Experimental Section method Measurement of thickness of individual layers and multilayer systems The thickness of the individual layers and of the multilayer system was measured by scanning electron microscopy.

[0126] Light transmittance measurement The light transmittance of layers L1 and L2 and the multilayer system of the present invention can be measured using ASTM D-1003 (Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics).

[0127] Measurement of effective luminous flux (useΦ) Luminous flux describes the amount of light emitted by a light source. Effective luminous flux (useΦ) describes the amount of luminous flux incident on a surface. Luminous flux was determined from photometric measurements using a goniophotometer to measure the luminous intensity distribution.

[0128] Determination of the Unified Glare Rating (UGR) The UGR value is calculated by the following formula (I):

number

[0129] This procedure is detailed in CIE 117:1995 or CIE 190:2010, respectively. UGR limits for indoor lighting are specified in EN 12464, while UGR limits for outdoor lighting are specified in EN 12464-2.

[0130] Refractive index measurement The refraction index or refractive index was measured using a refractometer at a wavelength of 589 nm.

[0131] Simulation of the effect of the transparent multilayer system of the present invention on the glare beam Simulations were performed using Fresnel equations to investigate the effect of the transparent multilayer system of the present invention on the glare beam emitted from a lighting fixture. Three different conditions were simulated. First, the reflection of light rays was simulated for a state-of-the-art glare control structure as layer L1 ("GCS"), known from Patent CH711562A1. Light propagation through the glare control structure was simulated for different apex angles, as shown in Table 1. Furthermore, an idealized case was simulated, in which the surface was assumed to only transmit incident light without reflecting it ("Transmission"). Next, light propagation was simulated for a multilayer system of the present invention, including the above-described glare control structure as layer L1 and layer L2 above L1, where L2 was formed of MgF2 with a dry layer thickness of 100 μm ("MgF2"). Thus, the "MgF2" condition includes the same glare control structure as the "GCS" condition. The conditions "GCS" and "MgF2" differ in that the glare control structure in the condition "GCS" is uncoated, whereas the glare control structure in the condition "MgF2" is coated with an MgF2 layer having a dry layer thickness of 100 μm.

[0132] To measure the level of glare, the Unified Glare Rating (UGR) was measured using CIE 117 and CIE 190. The lower the UGR value, the lower the glare effect.

[0133] [Table 1]

[0134] The UGR values ​​for all apex angles were lower under idealized conditions ("transmission") compared to the condition where an uncoated glare control structure was used ("GCS"). The UGR values ​​for example "GCS" represent the glare level when using a state-of-the-art glare control structure. The transparent multilayer system according to the present invention, which includes the CH711562A1 glare control structure as layer L1 and MgF2 as layer L2, reduced the glare level compared to the uncoated glare control structure. The lowest glare level using the transparent multilayer system according to the present invention was observed at 16.60 (CIE 117) or 15.20 (CIE 190) at an apex angle of 110°.

[0135] From the above data, the surface area of ​​the lighting fixture is 1m 2 The maximum effective luminous flux (klm) per (use Φ) was calculated for UGR=19 in a room size of 4H / 8H (and room conditions of 70% ceiling reflection, 50% wall reflection, and 20% floor reflection). Additionally, the increase in effective luminous flux of the transparent multilayer system of the present invention over an uncoated glare control structure was calculated for both CIE 117 and CIE 190. Additionally, the increase in effective luminous flux for an idealized case was calculated over an uncoated glare control structure. The increase in effective luminous flux is shown in parentheses. The effective luminous flux values ​​were simulated for the apex angles shown in Table 2.

[0136] [Table 2]

[0137] Under idealized conditions ("transmission"), the effective luminous flux values ​​were the highest at all apex angles tested. Lower effective luminous flux values ​​were observed with the glare control structure than under idealized conditions, which represented the effective luminous flux when using state-of-the-art glare control structures. The use of a transparent multilayer system comprising the glare control structure as layer L1 and MgF2 as layer L2 increased the effective luminous flux compared to the uncoated glare control structure. The highest effective luminous flux values ​​of 27.20 (CIE 117) or 40.70 (CIE 190) were observed at an apex angle of 110° when using the transparent multilayer system according to the present invention.

[0138] Using the transparent multilayer system according to the present invention, when forming an L2 layer by applying MgF2 onto the glare control structure, an increase in effective luminous flux of approximately 9.6% (CIE 117) or 16.1% (CIE 190) could be achieved at an apex angle of 110° compared to the use of an uncoated glare control structure. Thus, the additional coating of the glare control structure with an MgF2 layer improves the state-of-the-art glare control structure. Furthermore, this increase is close to the ideal case, with an effective luminous flux increase of approximately 14% achieved.

[0139] Thus, this simulation shows that glare beams are still observed when a glare control structure is used over a lighting fixture. Glare beams can arise, among other things, due to partial reflection and transmission of a portion of a light ray at each interface between two materials with different refractive indices. Therefore, when an uncoated glare control structure is used, glare beams are still observed because light rays that were previously partially reflected at the cone-air interface exit the cone structure at a propagation angle that causes glare. As a result, occupants of the illuminated space are still disturbed by the glare beams. However, coating the glare control structure with, for example, MgF2 reduces the glare beams, as demonstrated by the data shown in Tables 1 and 2. Thus, these glare beams are suppressed by the transparent multilayer system of the present invention. The simulation data was verified by preparing a transparent multilayer system of the present invention.

[0140] Preparation of the transparent multilayer systems of the present invention To validate the simulations outlined herein, an uncoated glare control structure ("GCS") was compared to a transparent multilayer system of the present invention, which included a coated glare control structure in which a layer of MgF2 having a dry layer thickness of 95 mm was coated onto the microstructure comprising the surface of the glare control structure ("MgF2").

[0141] A glare control structure was prepared according to CH711562A1 ("GCS") with an apex angle of 110°.

[0142] The glare control structure represents layer L1 of the inventive transparent multilayer system according to the present invention. To prepare the inventive transparent multilayer system, the glare control structure was coated with MgF2 by physical vapor deposition to form layer L2. The glare control structure (GCS) was prepared by roll-to-roll UV nanoimprint lithography on a polyethylene terephthalate substrate with a layer thickness of 250 μm.

[0143] The method for calculating effective luminous flux is as follows: The luminous intensity distribution of a light-emitting surface with approximately Lambertian luminous characteristics was measured with a glare control film on top (with an air gap between them). A goniophotometer was used for the measurement. UGR was calculated from the luminous intensity distribution, and from this, useΦ was calculated as described above. This was done for each sample in Table 3.

[0144] [Table 3]

[0145] The results shown in Table 3 highlight that the transparent multilayer system according to the invention increases the effective luminous flux, which can be achieved by suppressing the glare beam, as outlined in Table 1 herein. Thus, the simulations for the three conditions "GCS", "Transmission" and "MgF2" shown in Tables 1 and 2 were confirmed by the experimental data shown in Table 3. It is therefore assumed that any simulation of a multilayer system corresponds to the experimentally obtained data and thus provides a good prediction of the glare reduction due to the application of layer L2.

[0146] The transparent multilayer system according to the invention therefore improves on state-of-the-art glare control structures, in particular by suppressing glare beams that are observed due to light rays being partially reflected and transmitted by the glare control structure. As a result, the transparent multilayer system can be applied to light-emitting devices, such as luminaires, to provide a higher glare-free luminous flux. Furthermore, the occupants of the illuminated space are not disturbed by the glare beam.

Claims

1. Layer L １ and layer L ２ Including, a) Layer L １ is made of a transparent material, and the layer L １ at least one surface having a microstructure that provides glare control properties to the b) Layer L ２ But layer L ２ and one or more transparent materials that provide anti-reflective properties to the Layer L ２ The layer L having the microstructure １ on the surface of Transparent multilayer system.

2. Layer L １ 2. A transparent multilayer system according to claim 1, characterized in that said microstructures have a height in the range of 5 μm to 5000 μm.

3. Layer L １ The material forming the refractive index n is in the range of 1.35 to 2.00 measured at a wavelength of light of 589 nm. １ 3. A transparent multilayer system according to claim 1, characterized in that it comprises

4. Layer L １ 3. A transparent multilayer system according to claim 1, characterized in that it is formed from glass or a polymeric material or a blend of polymeric materials or a blend of polymeric and inorganic materials.

5. Layer L １ The polymeric material of the present invention is a plastic foil or a plastic sheet or a cured coating composition C １ 5. The transparent multilayer system according to claim 4, wherein

6. Layer L １ 3. A transparent multilayer system according to claim 1 or 2, characterized in that the microstructures are designed as cones, pyramids with a triangular or square base, inverted pyramids with a triangular or square base, prisms, Fresnel lens-like structures, microlens-like structures with a hexagonal or square lattice arrangement, a combination of two linear structures of prisms, or mixtures thereof, and / or the microstructures have a hexagonal, square or other lattice arrangement.

7. Layer L ２ 3. A transparent multilayer system according to claim 1 or 2, characterized in that is selected from the group of antireflective coating structures and / or the group of antireflective coating surfaces.

8. 8. The transparent multilayer system of claim 7, wherein the antireflective coating structure is selected from the group consisting of a single-layer antireflective coating, a double-layer antireflective coating, a multilayer antireflective coating, and a gradient refractive index coating, and the antireflective coating surface is selected from the group consisting of a porous layer, a biomimetic photonic nanostructure, and a textured surface.

9. Layer L ２ 3. A transparent multilayer system according to claim 1, wherein the material forming said coating layer is selected from the group consisting of silicon-based coating materials, metal-based coating materials, polymer-based coating materials and composite coating materials.

10. Layer L ２ is made of magnesium difluoride and has a dry layer thickness d in the range of 85 to 175 nm Ｌ 3. A transparent multilayer system according to claim 1, characterized in that it is a single anti-reflection coating layer having the formula:

11. Layer L １ but, Support layer L Ｓ on top of, or Adhesive layer L ａ on top of, or Adhesive layer L ａ The support layer L on top of Ｓ Above it, 3. A transparent multilayer system according to claim 1 or 2.

12. The following process i. A layer L comprising a microstructure on at least one surface, preferably one surface. １ followed by forming ii. below a. The layer L having the microstructure １ depositing one or more coating materials on said surface to form an anti-reflective coating layer L ２ or b. The layer L having the microstructure １ and partially removing material from the surface of layer L, thereby maintaining the shape of the microstructure. １ and an antireflection layer L made of the same material as ２ To form As a result, the anti-reflection layer L ２ The process of forming 3. A method for producing a transparent multilayer system according to claim 1, comprising:

13. Layer L in step i. １ 13. A method for producing a transparent multilayer system according to claim 12, characterized in that the microstructure of is formed by one or more of laser ablation, hot stamping, UV casting, injection molding, compression molding, a roll-to-roll process, an embossing process, a plasma etching process, a sol-gel process and / or 3D printing.

14. Layer L in step ii. ２ 13. A method for producing a transparent multilayer system according to claim 12, characterized in that is formed by one or more of the following techniques: sol-gel method, thermal evaporation, sputtering, glancing angle deposition (GLAD), chemical vapor deposition (CVD), wet and dry etching, lithography, focused ion beam techniques, nanoimprint techniques, microreplication, photoaligning and photopatterning.

15. A transparent multilayer system, characterized in that it is obtained by the method defined in claim 12.

16. 3. Use of a transparent multilayer system according to claim 1 or 2 as a glare-reducing component in a light-emitting device.

17. A luminaire comprising a light source and a transparent multilayer system as defined in claim 1 or 2.

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