Wavelength-selective multilayer and solar cell arrays containing the same

Abstract

A wavelength-selective multilayer is presented. This wavelength-selective multilayer includes a polymer multilayer optical film and an inorganic multilayer optical film. The polymer multilayer optical film reflects perpendicularly incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength range of 800 nanometers to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. The inorganic multilayer optical film reflects and absorbs perpendicularly incident light over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to 400 nm. The present invention also relates to a solar cell array including the wavelength-selective multilayer.

Description

[Background technology]

[0001] Photovoltaic ("PV") panels, also known as solar cell arrays or arrays of solar cells, are commonly used to generate electricity by converting incident light energy from the sun into electric current. Solar cells are most often constructed by laminating electrical components between two sheets of silicate glass, with the space between the glass sheets filled with a encapsulant, which is often a polymer matrix. Furthermore, solar cells are generally designed to absorb as much light energy as possible, so the materials used in their construction are often dark or black. These factors combine to cause solar cells to easily absorb a large amount of thermal energy from incident radiation, and their durability is limited because polymer encapsulants tend to chemically degrade under exposure to strong ultraviolet (UV) radiation and high-temperature loads. In addition, the degradation rate of the solar cell itself increases at high temperatures. Moreover, the efficiency of solar cells decreases under high-temperature conditions.

[0002] In some cases, solar cell arrays operate at altitudes ranging from 20 to 2000 km, where the thin atmosphere absorbs very little solar radiation. Therefore, high-altitude devices are exposed to a stronger solar spectrum, and particularly to ultraviolet C (UV-C) radiation, compared to conditions observed under the AM1.5 solar spectrum on Earth. Furthermore, the aforementioned problems become even more pronounced in the outer space environment. This is because the absence of atmospheric shielding increases the amount of infrared (IR) and ultraviolet (UV) light. [Overview of the project]

[0003] In a first embodiment, a wavelength-selective multilayer is provided. The wavelength-selective multilayer includes a polymer multilayer optical film having a first main surface and a second main surface opposite thereto. The polymer multilayer optical film includes one or more alternating first and second polymer optical layers that reflect as a whole light incident perpendicular to the first main surface of the wavelength-selective multilayer, and reflects at least 50%, 60%, 70%, 80%, 90%, or 95% of incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength range of 800 nanometers to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. The wavelength-selective multilayer also includes an inorganic multilayer optical film having a first main surface and a second main surface opposite thereto, wherein the second main surface of the inorganic multilayer optical film is bonded to the first main surface of the polymer multilayer optical film. The inorganic multilayer optical film comprises one or more alternating first and second inorganic optical layers that reflect and absorb as a whole light incident perpendicular to the first main surface of a wavelength-selective multilayer, and reflects and absorbs at least an average of 50%, 60%, 70%, 80%, 90%, or 95% of incident ultraviolet light over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to 400 nm.

[0004] In a second embodiment, a solar cell array is provided. The solar cell array includes a wavelength-selective multilayer according to the first embodiment, wherein the wavelength-selective multilayer is arranged on the outer surface of the solar cell array.

[0005] By combining inorganic and polymer multilayer optical films, the resulting multilayer has the advantage of exhibiting high transmittance in the visible and near-infrared regions, while having low transmittance in the ultraviolet and longer-wavelength infrared regions. Furthermore, at least some embodiments of the wavelength-selective multilayer exhibit favorably low transmittance to water vapor, oxygen, and / or other atmospheric gases. These effects can prevent these contaminants from corroding or degrading electronic components and encapsulants within the solar cell, thereby extending the lifespan of the solar cell. Another advantage of the preferred embodiments of this disclosure is that the wavelength-selective multilayer tends to improve the performance of the solar cell because the temperature rise is suppressed and the degradation rate is reduced even when exposed to incident light. In addition, the optional use of a structured film can reduce light loss due to reflection and improve light capture efficiency compared to a flat film. The inorganic layer and / or barrier layer can be formed by sputter deposition or evaporation in a roll-to-roll process. The polymer multilayer optical film can be formed by co-extrusion. Thus, a further advantage of the preferred embodiments of this disclosure is that it enables a high-speed roll-to-roll continuous production process for the wavelength-selective multilayer.

[0006] Various aspects and advantages of preferred embodiments of the Disclosure are summarized above. This summary is not intended to describe every or all of the embodiments of the Disclosure. Some preferred embodiments of the Disclosure using the principles disclosed herein are illustrated more specifically in the drawings and detailed description below. [Brief explanation of the drawing]

[0007] This disclosure can be better understood by considering a detailed description of each embodiment of this disclosure in connection with the accompanying drawings.

[0008] [Figure 1A] Figure 1A is a schematic cross-sectional view of an example of a wavelength-selective multilayer 10 and a solar cell array 40 according to each embodiment of the present disclosure.

[0009] [Figure 1B] Figure 1B is a schematic cross-sectional view of an example of another wavelength-selective multilayer body 10 and another solar cell array 40 according to each embodiment of the present disclosure.

[0010] [Figure 1C] Figure 1C is a schematic cross-sectional view of an example of a barrier layer used in an example of the present disclosure.

[0011] [Figure 2A] Figure 2A is a perspective view of a Cartesian coordinate system of a surface that can be used to explain various surfaces of a multilayer body.

[0012] [Figure 2B] Figure 2B is a schematic cross-sectional view of an example of a structured film used in an example of the present disclosure.

[0013] [Figure 2C] Figure 2C is a schematic cross-sectional view of an example of a part of a wavelength-selective multilayer body according to each embodiment of the present disclosure.

[0014] [Figure 2D] Figure 2D is a scanning electron microscope (SEM) image of a cross-section of a part of the wavelength-selective multilayer body 10 according to each embodiment of the present disclosure.

[0015] [Figure 3] Figure 3 is a perspective view of a structured surface including a linear array of prisms.

[0016] [Figure 4A] Figure 4A is a perspective view of a structured surface including an array of cubic corner elements.

[0017] [Figure 4B] Figure 4B is a perspective view of a structured surface including an array of pyramid elements.

[0018] [Figure 5]Figure 5 is a perspective view of a structured surface containing an array of cones.

[0019] [Figure 6] Figure 6 is a perspective view of a structured surface including a diffraction grating with a bias angle.

[0020] [Figure 7] Figure 7 is a perspective view of a structured surface containing an array of inverted pyramids.

[0021] In the drawings, the same reference numerals indicate the same element. The drawings specified above are not necessarily drawn to scale and are illustrative of the embodiments of the present disclosure, but other embodiments are also conceivable as described in the detailed description. In all cases, the present disclosure is explained by illustrative embodiments and should not be constrained. Those skilled in the art will understand that a number of other modifications and embodiments can be devised within the scope and spirit of the present disclosure. [Modes for carrying out the invention]

[0022] In the following glossary of definitions, these definitions shall apply throughout this application unless otherwise specified in the claims or elsewhere in this specification.

[0023] [Glossary] Throughout this specification and the claims, certain terms that are generally known but may require explanation are used. These are defined below.

[0024] The term "fluoropolymer" refers to any organic polymer that contains fluorine.

[0025] The term "nonfluorinated" means that it does not contain fluorine.

[0026] The terms “(co)polymer” or “(co)polymer(s)” include homo(co)polymers and (co)polymers, and also include homo(co)polymers or (co)polymers that may be formed in soluble mixtures by co-extrusion or reaction (including, for example, transesterification). The term “(co)polymer” includes random, block, and star(co)polymers.

[0027] As used herein, the term “adjacent” encompasses both cases where materials are in direct contact (i.e., directly adjacent) and cases where there is one or more intermediate layers between adjacent materials.

[0028] As used herein, the term “attached” encompasses both cases where materials are directly joined and cases where materials are joined via one or more intermediate layers.

[0029] As used herein, the term “incident” refers to light striking or irradiating a material.

[0030] The term "crosslinked (co)polymer" refers to a copolymer in which the (co)polymer chains are typically covalently linked by crosslinking molecules or groups, forming a network-like (co)polymer. Crosslinked (co)polymers are generally insoluble, but can swell in the presence of a suitable solvent.

[0031] The term "cure" refers to a process that causes a chemical change, such as a reaction that solidifies a multilayer film or creates covalent bonds that increase its viscosity.

[0032] The term "cured (co)polymer" includes both crosslinked and uncrosslinked (co)polymers.

[0033] The term "metal" includes pure metals or metallic alloys.

[0034] The terms "film" or "layer" refer to a single layer within a multilayer film.

[0035] The term "substrate" encompasses films and layers, and also includes structured films / layers.

[0036] The terms "(meth)acrylic" or "(meth)acrylate," when used in reference to monomers, oligomers, (co)polymers, or compounds, refer to vinyl-functional alkyl esters formed as reaction products of alcohol with acrylic acid or methacrylic acid.

[0037] The term "optically clear" refers to an article in which no visible distortion, cloudiness, or defects are detected when viewed with the naked eye from a distance of approximately 1 meter, preferably about 0.5 meters.

[0038] The term "optical thickness" refers to the product of the physical thickness of a layer and its in-plane refractive index.

[0039] The terms "vapor coating" or "vapor depositing" refer to the process of applying a coating from a vapor phase to a substrate surface, and include, for example, evaporating a precursor material or the coating material itself and then depositing it onto the substrate surface. Examples of vapor deposition processes include physical vapor deposition (PVD), chemical vapor deposition (CVD), and combinations thereof.

[0040] When the terms “overlaying” or “overcoated” are used to describe the location of different layers of the articles of this disclosure, it means that the layer is located on top of another layer, but not necessarily adjacent to or in contact with it. In some embodiments, the layer may be in direct contact with another layer.

[0041] When directional terms such as "atop," "on," "over," "covering," "uppermost," and "underlying" are used, they are intended to indicate the relative position of each element to a horizontally positioned and upward-facing substrate. However, unless otherwise explicitly stated, it is not intended that the substrate or article has a particular orientation in space during or after manufacturing, or when interpreting the claims.

[0042] In this specification, the term "radiation" refers to electromagnetic radiation unless otherwise specified.

[0043] As used herein, the term "refracting" refers to the change in the direction of light as it enters a material.

[0044] As used herein, the term "scattering" refers to the process by which light deviates from a straight path and travels in different directions and with different intensities.

[0045] As used herein, the term “reflectance” refers to the measurement of the proportion of light or radiation reflected when light or other radiation strikes a surface perpendicularly incident on it. Reflectance is usually wavelength-dependent and is expressed as a percentage of incident light reflected from the surface (0% = no reflection, 100% = total reflection). In this specification, “reflectivity” and “reflectance” are used as synonyms.

[0046] As used herein, the terms “reflective” and “reflectivity” refer to the property of reflecting light or radiation, and in particular to reflectance as a measurement independent of the thickness of the material.

[0047] As used herein, the term "average reflectance" refers to reflectance averaged over a specific wavelength range.

[0048] As used herein, the term "absorption" refers to the process by which a material converts the energy of light radiation into internal energy.

[0049] As used herein, the term “absorb” encompasses both absorption and scattering with respect to the wavelength of light, because scattered light is ultimately absorbed. Absorbance can be measured by the method described in ASTM E903-12, “Standard Test Method for Solar Absorbance, Reflectance and Transmittance of Materials Using an Integrating Sphere.” The absorbance measurements described herein were performed by first measuring the transmittance as described above, and then calculating the absorbance according to equation (1).

[0050] As used herein, the term "absorbance" refers to the common logarithm (base 10) of the ratio of incident radiant power to transmitted radiant power as it passes through a material, in the context of quantitative measurement. This ratio is expressed as the value obtained by dividing the radiant flux incident on the material by the radiant flux transmitted through the material. Absorbance (A) can be calculated based on the internal transmittance (T) according to equation (1).

number

[0051] Emissivity can be measured by an infrared imaging radiometer using the method described in ASTM E1933-14 (2018), "Standard Practice for Measurement and Correction of Emissivity Using an Infrared Imaging Radiometer." According to Kirchhoff's law of thermal radiation, absorbance correlates with radioactivity. In this specification, absorbance, absorptivity, emissivity, and radioactivity are used synonymously with respect to the same purpose of radiation of infrared energy into the atmosphere. Similarly, "absorb" and "emit" are used synonymously in this specification.

[0052] As used herein, the terms "transmittance" and "transmission" refer to the ratio of the total amount of light transmitted through a material layer to the amount of light incident on the material, taking into account effects such as absorption, scattering, and reflection. Transmittance (T) can range from 0 to 1, or can be expressed as a percentage (T%).

[0053] As used herein, the term “transparent” refers to a material (e.g., a film or layer) that absorbs less than 20% of light having wavelengths between 350 nanometers (nm) and 2500 nm.

[0054] As used herein, the term "bandwidth" refers to the width of a continuous range of wavelengths.

[0055] As used herein, the term “flexible” means that it can be wound around a roll core with a radius of curvature up to 7.6 centimeters (cm) (3 inches), and in some embodiments up to 6.4 cm (2.5 inches), 5 cm (2 inches), 3.8 cm (1.5 inches), or 2.5 cm (1 inch). In some further embodiments, the flexible laminate can be bent to a radius of curvature of at least 0.635 cm (1 / 4 inch), 1.3 cm (1 / 2 inch), or 1.9 cm (3 / 4 inch).

[0056] The terms "about" or "approximately" in relation to numerical values ​​or shapes mean within ±5% of the numerical value or characteristic, but also explicitly include its exact value.

[0057] The term "substantially" in relation to a characteristic or property means that the characteristic or property is more pronounced than the opposite characteristic or property. For example, a "substantially transparent substrate" refers to a substrate that transmits more radiation (e.g., visible light) than radiation that does not transmit (i.e., absorbs or reflects). Therefore, a substrate that transmits more than 50% of incident visible light is substantially transparent, while a substrate that transmits 50% or less is not substantially transparent.

[0058] As used herein and in the appended embodiments, the singular forms "a," "an," and "the" are interpreted as encompassing the plural unless the context clearly indicates otherwise. Therefore, for example, the term "a compound" includes a mixture of two or more compounds. Furthermore, as used herein and in the appended embodiments, the term "or" is used to mean "and / or" unless the context specifically indicates otherwise.

[0059] Unless otherwise explicitly stated, all numerical values ​​indicating quantities, components, property measurements, etc., in this specification and embodiments are understood to always be modified by the word “about.” Therefore, unless otherwise indicated, numerical parameters described herein and in embodiments may vary depending on the desired properties sought by a person skilled in the art using the teachings of this disclosure. Each numerical parameter should be interpreted with respect to the number of significant figures reported and common rounding techniques, although this does not limit the scope of the doctrine of equivalents.

[0060] By definition, the total weight percentage of all components in a composition is equal to 100% by weight.

[0061] Next, examples of embodiments of the present disclosure will be described. Embodiments of the present disclosure can be modified and altered in various ways without departing from the spirit and scope of the present disclosure. Accordingly, embodiments of the present disclosure are not limited to the exemplary embodiments described below, but are limited to the scope defined by the claims and their equivalents.

[0062] Wavelength-selective multilayer From a first perspective, a wavelength-selective multilayer is provided. This wavelength-selective multilayer includes the following components:

[0063] A polymer multilayer optical film having a first main surface and a second main surface opposite to it, wherein the polymer multilayer optical film is composed of one or more alternating layers of first and second polymer optical layers, which together reflect light incident perpendicularly to the first main surface of the wavelength-selective multilayer, and reflects an average of at least 50, 60, 70, 80, 90, or 95% of the incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength range of 800 nanometers to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm, and further,

[0064] An inorganic multilayer optical film having a first main surface and a second main surface opposite thereto, wherein the second main surface of the inorganic multilayer optical film is bonded to the first main surface of the polymer multilayer optical film, and the inorganic multilayer optical film is composed of one or more alternating layers of first and second inorganic optical layers, which together reflect and absorb light incident perpendicularly to the first main surface of the wavelength-selective multilayer, and reflect and absorb an average of at least 50, 60, 70, 80, 90, or 95% of the incident ultraviolet light over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to 400 nm.

[0065] Referring to Figure 1A, this disclosure describes a wavelength-selective multilayer 10 comprising a polymer multilayer optical film 20 and an inorganic multilayer optical film 30. The polymer multilayer optical film 20 is composed of one or more alternating layers of first polymer optical layers 23 (A-N) and second polymer optical layers 22 (A-N), which together reflect light incident perpendicularly to the first main surface 16 of the wavelength-selective multilayer 10, reflecting an average of at least 50, 60, 70, 80, 90, or 95% of the incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength ranges of 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. It should be understood that the wavelength-selective multilayer 10 is configured / oriented so that light is incident on the side including the first main surface 36 of the inorganic multilayer optical film. Any light source can be used, and the light source L shown in the figure represents the sun.

[0066] The polymer multilayer optical film 20 has a first main surface 26 and a second main surface 28 facing it. The inorganic multilayer optical film 30 has a first main surface 36 and a second main surface 38 facing it, and the second main surface 38 of the inorganic multilayer optical film 30 is bonded to the first main surface 26 of the polymer multilayer optical film 20. In the embodiment shown in Figure 1A, the polymer multilayer optical film 20 is not directly bonded to the inorganic multilayer optical film 30, but two optional components, namely a structured film 50 and an intermediate layer 60, are placed between these two multilayer optical films. The optional structured film 50 has a first main surface 56 and a second main surface 58 facing it, and the first main surface 56 includes a plurality of structures protruding therefrom. For the sake of simplification of the figure, these structures are not shown in the schematic diagram. A suitable structured film will be described later. In this configuration, the structured film 50 is usually a microstructured film. An arbitrary intermediate layer 60 is positioned between the second main surface 38 of the inorganic multilayer optical film 30 and the first main surface 26 of the polymer multilayer optical film 20. Suitable intermediate layers 60 include, for example (but not limited to), a tie layer, a barrier layer, or a combination thereof. Thus, the intermediate layer 60 shown in Figure 1A can represent any number of intermediate layers at that position in the overall structure. In certain embodiments, the intermediate layer 60 is a barrier layer. Suitable barrier layers will be discussed later.

[0067] Referring to Figure 1B, the disclosure further describes other wavelength-selective multilayers 10, including a polymer multilayer optical film 20 and an inorganic multilayer optical film 30, and a solar cell array 40, including the multilayer 10. The embodiment shown in Figure 1B differs from the embodiment shown in Figure 1A primarily in the position of the structured film 50. In Figure 1B, any structured film 50 is positioned adjacent to the second main surface 28 of the polymer multilayer optical film 20 (i.e., opposite to the inorganic multilayer optical film 30). In this configuration, the structured film 50 is typically a macrostructured film. Suitable macrostructured films can be prepared, for example, by thermoforming or embossing, and are described in detail in International Publication WO2014 / 035778 (Hebrink et al.), U.S. Patent No. 6,788,463 (Merrill et al.), or U.S. Patent No. 6,096,247 (Strobel et al.), all of which are incorporated herein by reference in their entirety. Considering both Figure 1A and Figure 1B, the structured film 50 may optionally be positioned either a) between the first main surface 26 of the polymer multilayer optical film 20 and the second main surface 38 of the inorganic multilayer optical film 30, or b) adjacent to the second main surface 28 of the polymer multilayer optical film 20 located on the opposite side of the inorganic multilayer optical film 30. If the macrostructured film 50 is located adjacent to the second main surface 28 of the polymer multilayer optical film 20, the polymer multilayer optical film 20 is superimposed on the macrostructured film 50, and therefore the polymer multilayer optical film 20 itself is also macrostructured.

[0068] Referring to Figure 2A, the multilayer can be characterized in three-dimensional space by superimposing a Cartesian coordinate system onto its structure. The first reference plane 224 is located at the center between the main surfaces 212 and 214. The first reference plane 224 (referred to as the yz plane) has its x-axis as its normal vector. The second reference plane 226 (referred to as the xy plane) extends substantially coplanar with surface 216 and has its z-axis as its normal vector. The third reference plane 228 (referred to as the xz plane) is located at the center between the first end face 220 and the second end face 222 and has its y-axis as its normal vector.

[0069] In some embodiments, the multilayer includes a structured film, the structured surface of which is three-dimensional at the macroscale. However, at the microscale (e.g., a surface region including two or more adjacent structures with valleys or channels between them), the base layer / base member can be considered planar with respect to the structure. The width and length of the structure lie in the xy-plane, and the height of the structure lies in the z-direction. Furthermore, the base layer is parallel to the xy-plane and perpendicular to the z-plane. The structured film will be described in detail later.

[0070] Referring again to Figure 2A, "light incident perpendicularly to the first main surface of the multilayer" means light that strikes the first main surface 216 of the multilayer perpendicular to the reference plane 226 (and parallel to the reference plane 224). If the multilayer includes a structured film, the multilayer is oriented such that light is incident on the first main surface from which multiple structures protrude (i.e., light does not strike the second main surface on the opposite side of the structured film).

[0071] Polymer multilayer optical film Referring again to Figure 1A, the wavelength-selective multilayer 10 includes a polymer multilayer optical film 20, which, as will be described in more detail below, is composed of one or more alternating layers of a first polymer optical layer 23 (A-N) and a second polymer optical layer 22 (A-N).

[0072] Typically, polymer multilayer optical films have a thickness of 2.0 micrometers or more, 10 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, or 100 micrometers or more, and are 1000 micrometers or less, 950 micrometers, 900 micrometers, 850 micrometers, 800 micrometers, 750 micrometers, 700 micrometers, 650 micrometers, 600 micrometers, 550 micrometers, 500 micrometers, 450 micrometers, 400 micrometers, 350 micrometers, or 300 micrometers or less. For example, films with a thickness in the range of 2 micrometers to 1000 micrometers, or 50 micrometers to 600 micrometers, are available.

[0073] As described above, the alternating stacking of multiple first and second polymer optical layers works together to reflect light incident perpendicularly to the first main surface of the wavelength-selective multilayer, reflecting an average of at least 50, 60, 70, 80, 90, or 95% of the incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength ranges of 800 nanometers to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. In some cases, the wavelength reflection bandwidth of the reflected light may be wider than at least 30 nanometers, for example, having a wavelength reflection bandwidth of at least 50 nanometers, 75 nanometers, 100 nanometers, 125 nanometers, 150 nanometers, or 175 nanometers.

[0074] The technique of reflecting light using multilayer reflective films, which consist of two or more polymer layers alternately laminated, is well known and is described, for example, in U.S. Patent No. 3,711,176 (Alfrey, Jr. et al.), U.S. Patent No. 5,103,337 (Schrenk et al.), International Publication No. WO96 / 19347 (Jonza et al.), and International Publication No. WO95 / 17303 (Ouderkirk et al.). The reflection and transmission spectra of a particular multilayer film depend primarily on the optical thickness of each layer. This optical thickness is defined as the product of the actual thickness of the layer and its refractive index. Therefore, by appropriately selecting the optical thickness of the layers according to the following formula, the film can reflect infrared, visible, or ultraviolet wavelengths λ M It can be designed to reflect light.

[0075] λ M =(2 / M)*D r

[0076] Polymer multilayer optical film Here, M is an integer representing a specific order of reflected light, and D r D represents the optical thickness of an optical repeating unit (also called a multilayer stack) composed of two or more polymer layers. Therefore, D r This is the sum of the optical thicknesses of each polymer layer constituting the optical repeating unit. rThe thickness is always half the wavelength λ of the primary reflection peak. By varying the optical thickness of the optical repeating units along the thickness direction of the multilayer film, it is possible to design multilayer films that reflect light over a broad wavelength range. This band is generally called the “reflection band” or “stop band”. In some embodiments, the reflection band has a steep spectral edge at long wavelengths (red side) and / or short wavelengths (blue side). For example, when it is desirable to design a reflective film or other optical material that reflects light over a specific range in the visible light region, such as a reflective film that reflects only green light, it is desirable to have a steep edge on both the red and blue sides of the reflection band. Sharpened reflective bandedge(s) are described in detail, for example, in U.S. Patent No. 6,967,778 (Wheatley et al.), which is incorporated herein by reference.

[0077] In one embodiment, the polymer multilayer optical film described herein can be manufactured using common processing techniques, such as those described in U.S. Patent No. 6,783,349 (Neavin et al.), which are incorporated herein by reference. Preferred techniques for imparting a controlled spectrum to the polymer multilayer optical film include, for example, 1) a method of controlling the thickness of co-extruded polymer layers with an axial rod heater, such as in U.S. Patent No. 6,783,349 (Neavin et al.); 2) timely feedback of the thickness profile during manufacturing using a thickness measuring device such as an atomic force microscope (AFM), transmission electron microscope (TEM), or scanning electron microscope (SEM); 3) optical modeling to generate a desired thickness profile; and 4) repeated adjustment of the axial rod based on the difference between the measured layer profile and the target layer profile.

[0078] In one embodiment, an optical polymer film or layered optical polymer film having first and second main surfaces is provided. “Film” means a planar form of a plastic material that is thick enough to stand on its own and thin enough to be bent, folded, molded, or creased without cracking. The thickness of the film depends on the desired application and manufacturing method.

[0079] In this specification, “Optical Film” refers to a reflective or partially reflective polymer film designed to exhibit desired reflection, transmission, absorption, or refraction properties when exposed to electromagnetic energy in a specific wavelength band. Therefore, ordinary transparent polymer films, such as polyester or polypropylene, are not considered “optical films” for the purposes of this disclosure, even if they exhibit some degree of reflection or glare when viewed from a particular angle. However, films exhibiting both reflectivity and transmission, i.e., partially transmitting films, are included within the scope of this disclosure. A preferred optical polymer film absorbs less than 25% of the irradiated radiant energy; more preferably less than 10%, and even more preferably less than 5%. Radiant energy is typically expressed as energy in a specific wavelength range and can be reflected in either specular or diffuse reflection. Reflectance may be isotropic (i.e., the film has the same reflective properties in both in-plane axial directions) or anisotropic (i.e., it has different reflective properties in the in-plane orthogonal axial directions). Differences in reflection characteristics along the in-plane axis can be adjusted by controlling the relationship between the refractive indices in each axial direction for each constituent material.

[0080] Optical films come in a variety of forms and are selected according to the desired application. Suitable examples include multilayer polarizers, visible and infrared reflectors, and color optical films as described in patent documents WO95 / 17303, WO96 / 19347, and WO97 / 01440. Furthermore, U.S. Patents 6,045,894 (Jonza et al.), 6,531,230 (Weber et al.), 5,103,337 (Schrenk et al.), 5,122,905 (Wheatley et al.), 5,122,906 (Wheatley), 5,126,880 (Wheatley et al.), 5,217,794 (Schrenk), 5,233,465 (Schrenk et al.), and 5,262,894 (Wheatley et al.) are also available. Examples include (et al.), No. 5,278,694 (Wheatley et al.), No. 5,339,198 (Wheatley et al.), No. 5,360,659 (Arends et al.), No. 5,448,404 (Schrenk et al.), No. 5,486,949 (Schrenk et al.), No. 4,162,343 (Wilcox et al.), No. 5,089,318 (Shetty et al.), No. 5,154,765 (Armanini), and No. 3,711,176 (Alfrey, Jr. et al.). There are also reissued patents RE31,780 (Cooper et al.) and RE34,605 ​​(Schrenk et al.), all of which are incorporated herein by reference.

[0081] An example of an optical film composed of an immiscible blend of two or more polymer materials is a blend structure having discontinuous polymer regions. These polymer regions have a cross-sectional diameter perpendicular to the principal axis that is on the order of a portion of the distance corresponding to the wavelength of light, resulting in reflective and transmission properties. Desired optical properties can also be obtained by orientation, such as in blend mirrors and polarizers. These are described in Patent Document WO97 / 32224 (Ouderkirk et al.), U.S. Patent No. 6,179,948 (Merrill et al.), and No. 5,751,388 (Larson), the full contents of which are incorporated herein by reference.

[0082] In one embodiment, the polymer optical layer of the first multilayer optical film is composed of a fluoropolymer, polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polypropylene (PP) copolymer, polyethylene (PE) copolymer, copolymer of ethyl acrylate and methyl methacrylate (CoPMMA), a blend of PMMA and polyvinylidene fluoride (PVDF), acrylate copolymer, polyurethane, polyethylene naphthalate (PEN), or a combination thereof.

[0083] If the first multilayer optical film contains a fluoropolymer, the polymer optical layer preferably contains a fluoropolymer independently selected from the following groups: copolymers of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride; copolymers of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE); polyvinylidene fluoride (PVDF); ethylene-chlorotrifluoroethylene (ECTFE) polymer; ethylene-tetrafluoroethylene (ETFE); perfluoroalkoxyalkane (PFA) polymer; fluorinated ethylene-propylene (FEP) polymer; polytetrafluoroethylene (PTFE); copolymers of TFE, HFP, and ethylene; polyvinyl fluoride (PVF); and combinations thereof.

[0084] Referring again to Figure 1A, the polymer multilayer optical film 20 includes a multilayer optical stack in which layers 22 and 23, composed of at least two materials (usually different polymers), are alternately stacked. The refractive index n1 of the high refractive index layer 23 in one in-plane direction is higher than the refractive index n2 of the low refractive index layer 22 in the same in-plane direction. Due to the refractive index difference at each interface of layers 22 and 23, a portion of the incident light is reflected. The transmission and reflection properties of the polymer multilayer optical film 20 are based on the coherent interference of light caused by the refractive index difference between layers 22 and 23 and their respective thicknesses. If the effective refractive index (or in-plane refractive index at normal incidence) differs between adjacent layers 22 and 23, their interfaces form a reflective surface. The reflection intensity of the reflective surface is the square of the difference in the effective refractive index of layers 22 and 23 (e.g., (n1-n2)). 2 This depends on the refractive index difference between layers 22 and 23. By increasing the refractive index difference between layers 22 and 23, improvements in optical performance (high reflectivity), thinning (thinner layers or fewer layers), and broadening of bandwidth can be achieved. In one embodiment, the refractive index difference in the in-plane direction is at least about 0.05, preferably greater than about 0.10, more preferably greater than about 0.15, and even more preferably greater than about 0.20.

[0085] In one embodiment, the materials of layers 22 and 23 have inherently different refractive indices. In another embodiment, at least one of the materials of layers 22 and 23 has stress-induced birefringence, and the refractive index (n) of this material is affected by the stretching process. By stretching the polymer multilayer optical film 20 in a uniaxial or biaxial direction, a film having various reflectances for incident light oriented to different polarization planes can be obtained.

[0086] Referring again to Figure 1A, in this embodiment, an optional third polymer optical layer 24(A-N) is included between at least one pair of first polymer optical layers 23(A-N) and second polymer optical layers 22(A-N). In some cases, the third polymer optical layer 24(A-N) can be selected to enhance interlayer adhesion within the polymer multilayer optical film. In one embodiment, the third polymer optical layer is an isotropic polymer layer.

[0087] Some polymer multilayer optical films include a structure in which optical polymer layers A, B, and C are arranged in the order ABCB as an optical repeating unit. An example of an optical film having an ABCB layer structure is described in U.S. Patent No. 6,667,095 (Wheatley et al.), which is incorporated herein by reference in its entirety.

[0088] In some cases, a 711 constructive interference (711) stack with 330 alternating optical layers (55 optical repeating units) can be modeled using an optical model described as a 4x4 transfer matrix method employing the Berreman algorithm, consisting of polymer A being PET (polyethylene terephthalate) and polymer B being CoPMMA (trademark Altuglas 510A, available from Arkema (Prussia, PA)). This optical model predicts an average reflectance of approximately 45% over the 850nm to 1850nm reflection band and an average visible light transmittance of 92% over the 400nm to 750nm transmission band. The transmitted CIE chromaticity values ​​were calculated as a*=-0.036 and b*=0.208. The reflected CIE chromaticity values ​​were calculated as a*=0.174 and b*=-0.769.

[0089] The Berreman algorithm was also used to model a 711 construction stack with 1290 alternating optical layers (215 optical repeating units) consisting of polymer A (PET) and polymer B (CoPMMA). This optical modeling predicts an average reflectance of 79% over the 850nm to 1850nm reflection band and an average visible light transmittance of 91% over the 400nm to 750nm transmission band. The transmitted CIE chromaticity values ​​were calculated as a*=-0.082 and b*=0.382. The reflected CIE chromaticity values ​​were calculated as a*=0.334 and b*=-1.382.

[0090] Furthermore, the 711 optical design is also described in International Publication No. WO2002 / 061469 (Liu et al.), which is incorporated herein by reference in its entirety.

[0091] In one embodiment, each third polymer optical layer includes a styrene-based block copolymer, an acrylic-based block copolymer, glycol-modified polyethylene terephthalate, glycol-modified polyethylene naphthalate, polymethyl methacrylate, a copolymer of methyl methacrylate and ethyl acrylate, anhydrous-modified ethylene vinyl acetate polymer, a ketone-ethylene-ester ternary copolymer, polycarbonate, a polyolefin-based thermoplastic elastomer, or a copolyethylene naphthalate-terephthalate copolymer. Typically, each third polymer optical layer has a different composition from the first and second polymer optical layers.

[0092] If one of the first and second polymer optical layers contains a fluoropolymer, the third polymer optical layer may contain, for example, polymethyl methacrylate (PMMA) or a copolymer of methyl methacrylate and ethyl acrylate (coPMMA). Acrylates (e.g., PMMA, coPMMA, acrylic block copolymers, or blends thereof) have been found to be particularly useful in providing high bonding strength with fluoropolymers (e.g., THV). Interlayer bonding between fluoropolymers (e.g., THV) and acrylates or other materials is described, for example, in U.S. Patent Publications 2019 / 0369314 (Hebrink et al.) and 2019 / 0111666 (Hebrink et al.).

[0093] In some embodiments, the average thickness of each third polymer optical layer is about 300 nm, 250 nm, 200 nm, 150 nm, 100 nm, 50 nm, 40 nm, 30 nm, 20 nm, 15 nm, 10 nm, or less than about 7.5 nm. In some such embodiments, or other embodiments, the average thickness of each third polymer optical layer is at least about 0.5 nm, 1 nm, 2 nm, or at least about 3 nm. For example, in some embodiments, the average thickness of each third polymer optical layer is in the range of about 1 nm to about 300 nm, or about 3 nm to about 200 nm.

[0094] According to several embodiments, a third polymer optical layer formed from a polymer with a low glass transition temperature, or a block copolymer containing a polymer block with a low glass transition temperature (e.g., soft), or a blend thereof, has been found to improve bonding with the first and second polymer optical layers described herein. The glass transition temperature of the third polymer optical layer, or the soft block of the third polymer optical layer, may be, for example, 105°C, 100°C, 90°C, 80°C, 70°C, 60°C, 50°C, 40°C, 30°C, 20°C, 10°C, 0°C, -10°C, -20°C, -30°C, -40°C, or less than -50°C. The glass transition temperature of the polymer block of the copolymer can be determined as the glass transition temperature of the homopolymer consisting of the monomer units of the polymer block. The block copolymer may also contain other (e.g., hard) blocks for mechanical properties (e.g., handling and / or low creep). For mechanical properties, (e.g., hard) blocks may have glass transition temperatures above, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or 105°C. In some embodiments, each third polymer optical layer is a chemically inert or substantially chemically inert polymer layer. That is, in some embodiments, the polymer does not form covalent bonds with the material of other polymer optical layers, or forms so few covalent bonds that it substantially does not affect bonding with any adjacent layer.

[0095] Atactic polystyrene (aPS) can be optionally blended with sPS (e.g., about 5 to about 30 wt% aPS) to adjust the refractive index of the resulting layer and / or reduce the haze of the layer (e.g., reduce crystallinity). Suitable THV polymers include, for example, those described in U.S. Patent Publication 2019 / 0369314 (Hebrink et al.) and available under the trademark DYNEON THV from 3M Company (St. Paul, MN). In some embodiments, THV may contain about 35 to about 75 mol% tetrafluoroethylene, about 5 to about 20 mol% hexafluoropropylene, and about 15 to about 55 mol% vinylidene fluoride. Suitable styrene-based block copolymers include KRATON G1645 and KRATON G1657, available from KRATON Polymers (Houston, TX). Suitable acrylic block copolymers include those available under the trademark KURARITY of Kuraray Co., Ltd. (Tokyo, Japan). PETG can be described as PET in which some glycol units of the polymer are replaced with different monomer units (typically derived from cyclohexanedimethanol). PETG can be produced, for example, by replacing some of the ethylene glycol used in the transesterification reaction that produces the polyester with cyclohexanedimethanol. A suitable PETG copolyester is GN071, available from Eastman Chemical Company (Kingsport, TN). PEN and coPEN can be produced, for example, by the method described in U.S. Patent No. 10,001,587 (Liu). Low-melting-point PEN is coPEN containing about 90 mol% naphthalenedicarboxylate groups based on total carboxylate groups, and is also known as coPEN90 / 10. Another useful coPEN is coPEN70 / 30, which contains about 70 mol% naphthalenedicarboxylate groups and about 30 mol% terephthalate dicarboxylate groups based on total carboxylate groups.More generally, coPEN Z / 100-Z can be used, where coPEN Z / 100-Z contains Z mol% of naphthalene dicarboxylate groups (typically more than 50 mol% and about 90 mol% or less) and (100-Z) mol% of terephthalate dicarboxylate groups based on the total carboxylate groups. Glycol-modified polyethylene naphthalate (PENG) can be described as PEN in which some glycol units of the polymer are replaced with different monomer units, for example, by substituting some of the ethylene glycol used in the transesterification reaction to produce polyester with cyclohexanedimethanol. PHEN can be produced similarly to PEN described in, for example, U.S. Patent No. 10,001,587 (Liu), but differs in that some of the ethylene glycol used in the transesterification reaction (e.g., about 40 mol%) is replaced with hexanediol. Suitable PET is available, for example, from Nan Ya Plastics Corporation, America (Lake City, SC). Suitable sPS is available, for example, from Idemitsu Kosan Co., Ltd. (Tokyo, Japan). Suitable PMMA is available, for example, from Arkema Inc. (Philadelphia, PA). Suitable anhydride-modified ethylene vinyl acetate polymers include, for example, those available under the trademark BYNEL from Dow Chemical (Midland, MI). Suitable ketone-ethylene-ester ternary copolymers include, for example, those available under the trademark BYNEL from Dow Chemical (Midland, MI). Suitable polyolefin thermoplastic elastomers include those available under the trademark ADMER from Mitsui Chemicals, Inc. (Tokyo, Japan).

[0096] PEN, PET, and PHEN are examples of thermoplastic polymers exhibiting positive birefringence, while sPS is an example of a thermoplastic polymer exhibiting negative birefringence. Whether a polymer exhibits positive or negative birefringence may depend on the geometry of the crystallites formed when the polymer is oriented, for example, as described in U.S. Patent No. 9,069,136 (Weber et al.). Suitable positively birefringent thermoplastic polymers include those that form crystallites with symmetry axes substantially aligned with the elongation direction, while suitable negatively birefringent thermoplastic polymers include those that form discotic unit cell structures where the smallest unit cell dimensions are substantially aligned with the elongation direction. Styrene-based block copolymers, PMMA, coPMMA, THV, acrylic-based block copolymers, coPEN, and PETG are examples of thermoplastic polymers that can become substantially isotropic after orientation. Substantially isotropic polymers typically do not substantially form crystallites during orientation, or the crystallites melt and disappear when a film containing the polymer is heat-set. Further examples of positive and negative birefringent thermoplastic polymers and isotropic thermoplastic polymers are described, for example, in U.S. Patent No. 9,069,136 (Weber et al.). Other suitable materials for each layer of the multilayer optical film 300 include, for example, those described in U.S. Patents No. 5,103,337 (Schrenk et al.), No. 5,540,978 (Schrenk), No. 5,882,774 (Jonza et al.), No. 6,179,948 (Merrill et al.), No. 6,207,260 (Wheatley et al.), No. 6,783,349 (Neavin et al.), No. 6,967,778 (Wheatley et al.), No. 9,069,136 (Weber et al.), and No. 9,162,406 (Neavin et al.).

[0097] The number of layers in the polymer multilayer optical film 20 is selected to achieve the desired optical properties with the minimum number of layers, from the viewpoint of film thickness, flexibility, and economy. In the case of reflective films such as mirrors, the number of layers is preferably less than about 2000, more preferably less than about 1000, and even more preferably less than about 750. In some embodiments, the number of layers is at least 150 or 200. In other embodiments, the number of layers is at least 250.

[0098] Each constituent layer of a polymeric multilayer optical film may be resistant to ultraviolet light. Many fluoropolymers are resistant to ultraviolet light. Examples of fluoropolymers that can be used include copolymers of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (e.g., available as 3M DYNEON THV); copolymers of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE) (e.g., available as 3M DYNEON THVP); polyvinylidene fluoride (PVDF) (e.g., 3M DYNEON PVDF 6008); ethylene-chlorotrifluoroethylene polymer (ECTFE) (e.g., available as HALAR 350LC ECTFE from Solvay (Brussels, Belgium)); and ethylene-tetrafluoroethylene copolymer (ETFE) (e.g., 3M DYNEON ETFE from 3M). Examples include: available as 6235; perfluoroalkoxyalkane polymers (PFA); fluoroethylene-propylene copolymers (FEP); polytetrafluoroethylene (PTFE); and copolymers of TFE, HFP, and ethylene (HTE) (e.g., available as 3M DYNEON HTE1705 from 3M). Combinations of fluoropolymers may also be used. In some embodiments, the fluoropolymer includes FEP. In some embodiments, the fluoropolymer includes PFA. In some embodiments, the fluoropolymer includes PVF.

[0099] Examples of non-fluorinated polymers that can be used in at least one layer of a polymeric multilayer optical film include at least one of the following: PET, polypropylene copolymer, polyethylene copolymer, polyethylene methacrylate copolymer, polymethyl methacrylate, methyl methacrylate copolymer (e.g., copolymer of ethyl acrylate and methyl methacrylate), polyurethane, acrylate copolymer, stretched-chain polyethylene polymer (ECPE), polyethylene naphthalate (PEN), or combinations thereof. In general, combinations of non-fluorinated polymers can be used. Examples of non-fluorinated polymers, especially for use in high refractive index optical layers, include homopolymers of polymethyl methacrylate (PMMA) (e.g., CP71 and CP80 from Ineos Acrylics, Inc. (Wilmington, DE)) and polyethyl methacrylate (PEMA), which has a lower glass transition temperature than PMMA. Suitable polyethylene naphthalate (PEN) polymers are available under the trademark “Teonex Q51” from DuPont Teijin (Chester, VA). Further useful polymers include copolymers of methyl methacrylate (e.g., copolymers consisting of 75% by weight methyl methacrylate and 25% by weight ethyl acrylate, available as PERSPEX CP63 from Ineos Acrylics, Inc., or as ALTUGLAS 510 from Arkema (Philadelphia, PA)), and copolymers of methyl methacrylate units and n-butyl methacrylate units. Blends of PMMA and PVDF may also be used.

[0100] Suitable triblock acrylic copolymers are available, for example, under the trademark KURARITY LA4285 from Kuraray America Inc. (Houston, TX). Other suitable polymers for use in optical layers, particularly refractive index optical layers, include at least one of the following: polyolefin copolymers (e.g., poly(ethylene-co-octene) (available as ENGAGE 8200 from Dow Elastomers (Midland, MI)), polyethylene methacrylate (available as ELVALOY from Dow Elastomers), poly(propylene-co-ethylene) (available as Z9470 from Atofina Petrochemicals, Inc. (Houston, TX))), and copolymers of atactic polypropylene and isotactic polypropylene. Materials may be selected based on the absorption or transmission properties, as well as the refractive index, as described herein. Generally, the greater the refractive index difference between the two materials, the thinner the film can be made.

[0101] Multilayer optical films can be manufactured by alternately co-extruding polymer layers with different refractive indices. Examples of such patents are listed in U.S. Patent No. 5,882,774 (Jonza et al.), No. 6,045,894 (Jonza et al.), No. 6,368,699 (Gilbert et al.), No. 6,531,230 (Weber et al.), No. 6,667,095 (Wheatley et al.), No. 6,783,349 (Neavin et al.), No. 7,271,951B2 (Weber et al.), No. 7,632,568 (Padiyath et al.), No. 7,652,736 (Padiyath et al.), No. 7,952,805 (McGurran et al.), and International Publication No. WO95 / 17303 (Ouderkirk et al.), and WO99 / 39224 (Ouderkirk et al.).

[0102] In one embodiment, a polymer multilayer optical film contains a third-order harmonic and reflects at least 80%, 90%, or 95% of light incident perpendicularly to the first principal surface of the wavelength-selective multilayer in a wavelength bandwidth of at least 30 nm. This reflection occurs in the wavelength ranges of 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm. As described in U.S. Patent No. 6,667,095 (Wheatley et al.) and No. 5,360,659 (Arends et al.), a multilayer optical film formed by a quarter-wavelength interference filter with two materials stacked alternately produces higher-order reflections at wavelengths that are integer fractions of the principal reflection band. For example, the third harmonic appears at one-third of the wavelength range of the principal reflection band, the fifth harmonic appears at one-fifth of the wavelength range of the principal reflection band, and so on. For example, the “Example 16” IR film made of PET and polyethylene-co-octene (PE-PO) described in U.S. Patent No. 6,744,561 (Condo et al.) has a main reflection band that reflects light from 1020 nm to 1200 nm, but its third harmonic reflection band corresponds to 340 nm to 400 nm, i.e., one-third of the wavelength range of the main wavelength band. Examples of suitable polymer pairs that can be used for the first and second optical layers include, but are not limited to, polyethylene terephthalate (PET) / coPMMA, PMMA / polydimethylsiloxane-oxamide segmented copolymer (SPOX), thermoplastic polyurethane (TPU) / SPOX, ethylene-vinyl acetate (EVA) / SPOX, ethylene-methyl acrylate (EMA) / SPOX, and cyclic olefin copolymer (COC) / SPOX. By achieving reflection in these wavelength ranges, the amount of ultraviolet reflection / absorption that needs to be achieved by the inorganic multilayer optical film is reduced. As a result, the number of inorganic layers can be reduced, which has the advantage of producing a lower-cost product.

[0103] Typically, the average thickness of polymer multilayer optical films is between 50 micrometers and 250 micrometers, for example, 50 micrometers or more, 55 micrometers, 60 micrometers, 65 micrometers, 70 micrometers, 75 micrometers, 80 micrometers, 85 micrometers, 90 micrometers, or 95 micrometers or more, and 250 micrometers or less, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, or 60 micrometers or less.

[0104] Inorganic multilayer optical film Referring again to Figure 1A, the wavelength-selective multilayer 10 includes an inorganic multilayer optical film 30 comprising one or more alternating first inorganic optical layers 33 (A-N) and second inorganic optical layers 32 (A-N). The inorganic multilayer optical film 30 has a first main surface 36 and an opposing second main surface 38, the second main surface 38 of the inorganic multilayer optical film 30 being bonded (directly or indirectly) to the first main surface 26 of the polymer multilayer optical film 20.

[0105] The alternating first and second inorganic optical layers reflect and absorb light incident perpendicularly to the first main surface of the wavelength-selective multilayer, reflecting and absorbing at least 50, 60, 70, 80, 90, or 95% (preferably at least 80, 90, or 95%) of the incident ultraviolet light on average over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength range of 190 nanometers (nm) to 400 nm.

[0106] In some cases, the alternating first and second inorganic optical layers reflect and absorb light incident perpendicularly to the first main surface of the wavelength-selective multilayer, reflecting and absorbing at least 60, 70, 80, 90, or 95% of the incident ultraviolet light on average over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength ranges of 190 nm to 240 nm, 240 nm to 300 nm, 300 nm to 350 nm, 350 nm to 400 nm, or any combination thereof.

[0107] Optionally, alternating first and second inorganic optical layers reflect and absorb light incident perpendicularly to the first main surface of the wavelength-selective multilayer, reflecting and absorbing at least 60, 70, 80, 90, or 95% of the incident ultraviolet light on average over wavelength reflection bandwidths wider than 30 nanometers in the wavelength range of 190 nm to 400 nm, for example, at least 50 nanometers, 75 nanometers, 100 nanometers, 125 nanometers, 150 nanometers, or 175 nanometers.

[0108] Because the alternating first and second inorganic optical layers reflect and absorb light, some of the incident ultraviolet light may be absorbed and some of the rest may be reflected. In some cases, the alternating first and second inorganic optical layers absorb at least 30, 40, 50, 60, 70, 80, 90, or 95% of the incident light on average over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to less than 350 nm. In other cases, the alternating first and second inorganic optical layers reflect at least 30, 40, 50, 60, 70, 80, 90, or 95% of the incident light on average over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to less than 400 nm, 190 nm to 240 nm, 240 nm to 300 nm, 300 nm to 350 nm, 350 nm to less than 400 nm, or any combination thereof.

[0109] In certain embodiments of the wavelength-selective multilayer, alternating first and second inorganic optical layers transmit light incident perpendicularly to the first main surface of the wavelength-selective multilayer, transmitting at least 50, 60, 70, 80, 90, or 95% of the incident light on average in the visible light region. The wavelength range is from 400 nm to 700 nm, from 400 nm to 1100 nm, or from 400 nm to 1350 nm.

[0110] In certain embodiments of the wavelength-selective multilayer, the outermost inorganic layer is a second inorganic optical layer (e.g., 32A shown in Figure 1A), with a thickness of at least 70 nm. This reduces the amount of reflected light on the outer surface of the product and increases the transmission of light in the 400 nm to 700 nm range. This effect is particularly useful when the wavelength-selective multilayer is used in solar cell array applications, allowing visible light to reach the solar cells within the array.

[0111] In certain embodiments, at least one of the first optical layers closest to the outer surface of the film (e.g., 33A in Figure 1A) or the first optical layer closest to the polymer multilayer optical film (e.g., 33N in Figure 1A) has a thickness of 95%, 90%, 85%, or 80% or less of the thickness of the other first optical layer. This reduces the amount of light reflected in the 400 nm to 700 nm range from the outer surface of the wavelength-selective multilayer. This effect is particularly useful when the wavelength-selective multilayer is used in solar cell array applications, allowing visible light to reach the solar cells within the array.

[0112] In some embodiments, the wavelength-selective multilayer (e.g., as a whole) transmits, on average, at least 50, 60, 70, 80, 90, or 95% of the vertically incident visible light in a wavelength range from above 400 nm to up to 700 nm, from above 400 nm to up to 1100 nm, or from above 400 nm to up to 1350 nm. Achieving such visible light transmittance is particularly useful when the wavelength-selective multilayer is used for solar cell array applications, allowing visible light to reach the solar cells of the array. Further, the wavelength-selective multilayer according to certain preferred embodiments of the present disclosure has an average transmittance in a wavelength range from above 400 nm to up to 700 nm, from above 400 nm to up to 1100 nm, or from above 400 nm to up to 1350 nm that decreases by less than 20%, less than 10%, less than 5%, or less than 1% after exposure to a specific ultraviolet irradiation dose (e.g., the irradiation dose expressed in units of joules per square centimeter (J / cm 2 )). Similarly, the wavelength-selective multilayer of the present disclosure may be characterized in that its average reflectance in a wavelength range of 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm decreases by less than 20%, less than 10%, less than 5%, or less than 1% even after ultraviolet irradiation. For example, it may be exposed to an irradiation dose of 425 megajoules per square centimeter (MJ / cm 2 ), 470 MJ / cm 2 , or 850 MJ / cm 2 .

[0113] Typically, the thickness of the inorganic multilayer optical film is 200 nm or more, 250 nm, 300 nm, 350 nm, 400 nm, 500 nm, or 550 nm or more, and 1500 nm or less, 1400 nm, 1300 nm, 1200 nm, 1100 nm, 1000 nm, 900 nm, 850 nm, 800 nm, 750 nm, 700 nm, 650 nm, or 600 nm or less. For example, it has a thickness of 200 nm to 1500 nm.

[0114] In some cases, the first optical layer of an inorganic multilayer optical film includes at least one of niobium oxide, titanium oxide, silicon oxynitride, molybdenum oxide, tungsten oxide, silicon nitride, indium tin oxide, hafnium oxide, tantalum oxide, zirconium oxynitride, zirconium oxide, aluminum zinc oxide, or zinc oxide. As is well known to those skilled in the art, alloys of oxides are also applicable. The second optical layer of an inorganic multilayer optical film may also include at least one of silicon oxide, silicon-aluminum oxide, N-type or P-type doped silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, indium tin oxide, or zinc oxide. In certain embodiments of the inorganic multilayer optical film, the first optical layer includes at least one of niobium oxide or titanium oxide, and the second optical layer includes silicon-aluminum oxide. Similarly, in other embodiments, the first optical layer includes at least one of niobium oxide or titanium oxide, and the second optical layer includes silicon oxide. Such inorganic multilayer optical films have the advantage of also imparting antistatic properties to wavelength-selective multilayers.

[0115] When using photoactive inorganic materials such as titanium oxide, a non-photoactive material (e.g., silicon oxide, aluminum oxide, etc.) is usually placed between the photoactive inorganic material and the organic layer to minimize degradation of the organic layer. For example, referring again to Figure 1A, a layer made of a non-photoactive material may be placed as an intermediate layer 60 between the first optical layer 33N and (optionally) the structured film 50 or polymer multilayer optical film 20.

[0116] The inventors unexpectedly discovered that light in the UVA, UVB, and UVC regions can be shielded from an additional layer (e.g., a solar cell array 70). This can be achieved solely by the combined reflectance and absorptance of multiple alternating first and second inorganic optical layers, while maintaining a range that allows for the transmission of visible light (e.g., at least 50% of incident visible light).

[0117] Optical thin film laminate designs composed of alternating thin layers of inorganic dielectric materials with refractive index contrast are particularly well-suited for inorganic multilayer optical films. Over the past several decades, these have been applied in the UV, visible, NIR, and IR spectral regions. Depending on the target spectral region, specific materials suitable for that region exist. Furthermore, one of two forms of physical vapor deposition (PVD), namely evaporation or sputtering, is used to coat these materials. The evaporation method relies on heating the coating material (evaporation source) to its evaporation temperature and condensing the vapor onto the substrate. Electron beam evaporation is the most common method for vapor deposition coating dielectric mirrors. In sputtering, high-energy gas ions strike the surface of the material ("target"), and the emitted atoms condense onto nearby substrates. The deposition rate and structure-properties of the thin film are greatly influenced by the coating method used and its settings. Ideally, the coating rate should be high enough to obtain a dense, low-stress, void-free, and light-absorbent coating layer, while maintaining acceptable process throughput and film performance.

[0118] The number of optical layers is selected to achieve the desired optical properties with the minimum number of layers, from the viewpoint of film thickness, flexibility, and cost-effectiveness. Those skilled in the art will understand that such deposition techniques can be extended to chemical vapor deposition (CVD), atomic layer deposition (ALD), and other vapor deposition methods. Typically, the total number of layers is preferably 21 or fewer, 19, 17, 15, or 13 or fewer, and may require 3 or more, 5, 7, 9, or 11 or more layers. In certain embodiments, the inorganic multilayer optical film is formed from at least one first optical layer and two second optical layers.

[0119] The thicknesses of the first and second optical layers can vary considerably. For example, in some cases, the first and second optical layers may independently have thicknesses of 5 nm or more, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, or 70 nm or more, or thicknesses of 2000 nm or less, 500 nm, 145 nm, 140 nm, 135 nm, 130 nm, 125 nm, 120 nm, 115 nm, 110 nm, 105 nm, 100 nm, 95 nm, 90 nm, 85 nm, 80 nm, or 75 nm or less. In certain embodiments, each of the first and second optical layers of an inorganic multilayer optical film may independently have a thickness of 20 nm to 400 nm.

[0120] The inorganic multilayer optical films described herein can be manufactured, for example, using the general process techniques described in U.S. Patent No. 6,783,349 (Neavin et al.), the entire disclosure of which is incorporated herein by reference.

[0121] In the manufacture of inorganic coatings, the electron beam method is best suited for coating individual components. Optionally, UV shields can also be manufactured as large-area products using a continuous roll-to-roll (R2R) method. While R2R film coating has been demonstrated in some chambers, layer-by-layer deposition sequences are still required. For R2R sputtering of wavelength-selective multilayer 10 with an inorganic UV shielding layer, it is advantageous to use a sputtering system with multiple sources arranged around one or two coating drums. Here, in the case of a 13-layer optical stacked structure design, a process of continuously depositing high-refractive-index and low-refractive-index layers alternately is possible in two, or possibly one, machine passes. The number of machine passes required depends on the equipment design, cost, and the practicality of the 13 continuous sources. Furthermore, the deposition rate needs to be adjusted to match the single film line speed.

[0122] The film roll transport is started at a preset speed, the sputter source power is ramped up to full operation, and then a reactive gas is introduced to reach a steady state. The process continues until a predetermined length of film is reached, depending on the length of film to be coated. Here, the sputter source is perpendicular to the film to be coated and wider than the film, so the uniformity of the film thickness is very high. When the predetermined length of coated film is reached, the reactive gas is set to zero and the target is sputtered to a pure metal surface state. Next, the direction of film movement is reversed, and AC frequency (40 kHz) power is applied to a pair of rotating sputter targets in an argon atmosphere. After reaching a steady state, an oxygen reactive gas is introduced to obtain transparency and a low refractive index. Under predetermined process conditions and line speed, a second layer is deposited over the length to which the first layer was deposited. These sputter sources are also perpendicular to the film and wide, so the uniformity of the film thickness is very high. When the predetermined length of coated film is reached, the reactive oxygen is removed and the target is sputtered in argon to a pure metal surface state. Depending on the optical design, layers 3 through 5 (or 7, 9, 11, 13, etc.) are deposited in this sequence. After deposition is complete, the film roll is removed and moved to the post-processing stage.

[0123] Structured film Referring again to Figure 1A, in some embodiments, the wavelength-selective multilayer 10 further comprises a structured film 50, which is positioned between a first main surface 26 of the polymer multilayer optical film 20 and a second main surface 38 of the inorganic multilayer optical film 30. Referring to Figure 2B, a schematic cross-sectional view of the structured film 200 is shown, which includes a plurality of structures 240 suitable for a typical embodiment of the present disclosure. A structure having a surface with a slope such that light incident perpendicularly to the first main surface of the structured film is reflected and then returns to the first main surface of the structured film or the surface of at least one other structure means that light ("I") incident perpendicularly to the first main surface 230 of the structured film 200 strikes the surface of the structure 240a, and the structure 240a has a slope 242 such that reflected light ("R") reaches the surface of the first main surface of the structured film (not shown) or another structure 240b. Similar to the above description relating to the embodiment shown in Figure 2A, the first main surface 230 of the structured film 200 is considered to be parallel to the second main surface 210 of the structured film 200. The inclination (i.e., inclined surface) 242 of the structure 240a is defined by dividing the height 241 of the structure 240a by the width 243 between the peak (i.e., the high end of the inclined surface) 245 and the bottom (i.e., the low end of the inclined surface) 247. Another way to determine the inclination is to use the following formula:

number

[0124] Figure 2C is a schematic cross-sectional view of a portion of a wavelength-selective multilayer 10 according to at least some representative embodiments of the present disclosure. The portion of the wavelength-selective multilayer 10 includes a structured film 50 having a first main surface 56 and a second main surface 58 opposite to it. The first main surface 56 includes a plurality of structures 57 protruding therefrom. The wavelength-selective multilayer 10 includes an inorganic multilayer optical film 30 disposed on these plurality of structures 57. The inorganic multilayer optical film 30 includes alternatingly laminated first inorganic optical layers 33 and second inorganic optical layers 32. In this embodiment, the multilayer 10 further includes at least one intermediate layer 60 disposed between the structured film 50 and the inorganic multilayer optical film 30.

[0125] Figure 2D is a scanning electron microscope (SEM) image of a partial cross-section of a wavelength-selective multilayer 10 according to at least some representative embodiments of the present disclosure. The wavelength-selective multilayer 10 includes a structured film 50 having a first main surface 56. The first main surface 56 includes a plurality of structures 57 protruding therefrom. An inorganic multilayer optical film 30 is disposed on these plurality of structures 57. The inorganic multilayer optical film 30 includes first and second inorganic optical layers that are alternately stacked (the individual layers are too thin to be seen in the image). The second inorganic optical layer 32 is the outer layer. In this embodiment, the multilayer 10 further includes an intermediate layer 60 disposed between the structured film 50 and the inorganic multilayer optical film 30.

[0126] The structured film has a first main surface and a second main surface opposite it, with a plurality of structures protruding from the first main surface. At least some of the plurality of structures have surfaces with an inclination such that light incident perpendicularly to the first main surface of the structured film reaches the first main surface of the structured film or the surface of at least one other structure after reflection. Therefore, structures of various shapes are applicable. For example, in some cases the structures have the shape of a prism, pyramid, inverted pyramid, diffraction grating, inverted cone, or cone. These shapes will be described later. Furthermore, inverted shapes of any of these shapes are also applicable. The number of faces of the three-dimensional shape is arbitrary, for example, a four-faced pyramid, a five-faced pyramid, a six-faced pyramid, etc. In certain embodiments, each structure has the same size and shape, which makes it easier to obtain consistent optical properties of the multilayer optical film deposited over the entire surface of the structured film.

[0127] Optionally, at least some of the structures have a triangular cross-sectional shape, as shown in structures 240 and 57 in Figures 2B and 2C. Although not required, in some cases, at least some of the structures 240 include at least one inclined sidewall (e.g., 242) where the peak 245 forms a pointed tip. Advantageously, it has been confirmed that multilayer optical films can be formed on structures where the peak forms a pointed tip (i.e., structures where the peak is not rounded), and that "pinholes" due to insufficient deposition of the multilayer optical film on the peak apex do not occur.

[0128] In some cases, as shown in Figure 2B, at least a portion of the structure 240 includes at least one inclined side wall (e.g., 242) having a vertex angle θ. The vertex angle θ is 90 degrees or less, 85 degrees, 80 degrees, 75 degrees, 70 degrees, 65 degrees, 60 degrees, 55 degrees, 50 degrees, or 45 degrees or less, and can be 5 degrees or more, 7 degrees, 10 degrees, 12 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, or 50 degrees or more. In this specification, “vertex angle” means the angle between opposing side walls at the vertex of the structure.

[0129] 240 can optionally have an aspect ratio of (overall) width W to height H (i.e., H:W) of 10:1 or less, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, or 1:1 or less, and at least 1:2.

[0130] In some cases, the structures are macrostructures. Typically, macrostructures have a height exceeding 500 micrometers, specifically 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm or more, and a length of 10 millimeters (mm) or less, 9.5 mm, 9 mm, 8.5 mm, 8 mm, 7.5 mm, 7 mm, 6.5 mm, 6 mm, 5.5 mm, 5 mm, 4.5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, or 1.5 mm or less.

[0131] In some cases, the structure is a microstructure. Typically, microstructures have a height of 0.5 micrometers or more, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 150 μm The particles are μm, 175μm, 200μm, 225μm, or 250μm or larger, and 500μm or less, 475μm, 450μm, 425μm, 400μm, 375μm, 350μm, 325μm, 300μm, 275μm, 250μm, 225μm, 200μm, 175μm, 150μm, 125μm, 100μm, 75μm, 50μm, or 25μm or less.

[0132] Referring to Figure 3, in one embodiment, the first main surface 300 of the structured film 100 includes a linear arrangement of conformal prisms 320. Each prism has a first surface (i.e., an inclined surface) 321 and a second surface 322. The prisms are formed on a substrate 310, which has a first planar surface 331 (parallel to the reference plane 126) on which the prisms are formed, and a substantially flat or planar opposing second surface 332. It is assumed that the second surface 332 may also be structured. "Conformal prism" means one whose apex angle θ(340) is typically about 90 degrees, however this angle may vary within the range described above. These peaks may be acute or rounded, as shown in the figure. The spacing between (prism) peaks is characterized as pitch (P). In this embodiment, the pitch is also equal to the maximum width of the valleys. The pitch can range from 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 micrometers up to 250 micrometers. The length (L) of the (prism) structure is usually the maximum dimension and can extend over the entire length of the structured surface.

[0133] In other embodiments, the first main surface of the structured film may have a surface shape identical to that of the cube corner retroreflective sheet. Referring to Figure 4A, the cube corner retroreflective sheet typically comprises a thin transparent layer having a substantially planar surface and a structured surface 410 on the opposite side, the structured surface 410 comprising a plurality of cube corner elements 417. The structured surface 410 in Figure 4A is characterized as an array of cube corner elements 417 defined by three sets of parallel grooves (i.e., valleys) 411, 412, and 413. Two sets of grooves (valleys) intersect each other at angles greater than 60 degrees, and a third set of grooves (valleys) intersects each of the other two sets at angles less than 60 degrees to form corresponding pairs of inclined cube corner elements (see U.S. Patent No. 4,588,258 [Hoopman]). The groove angles are selected such that the dihedral angles formed at the intersection lines of the grooves, i.e., at 414, 415, and 416 in representative cube corner elements 417, are approximately 90 degrees. In some embodiments, one angle of the triangular base is at least 64, 65, 66, 67, 68, 69, or 70 degrees, and the other angles are 55, 56, 57, or 58 degrees.

[0134] In another embodiment, as shown in Figure 4B, the first main surface of the structured film 400 is characterized as an array of pyramidal peak structures 420 defined by two sets of parallel grooves (i.e., valleys) extending in the x and y directions. The base of the pyramidal peak structures is polygonal, and is usually square or rectangular depending on the spacing of the grooves. The apex angle θ(440) is usually about 90 degrees, but can vary within the range described above.

[0135] In some cases, the structure has a conical shape. Referring to Figure 5, the structured surface 500 of the structured film includes an array of cones 540. Each conical structure typically has only one inclined side wall 542. The apex 545 of each cone may be pointed or rounded.

[0136] Figure 6 shows a schematic diagram of the first main surface 600 of a structured film equipped with a diffraction grating having a bias angle. The second main surface 610 of the structured film defines a longitudinal axis (LA) along its longitudinal direction, and a plurality of structures 640 extend over the first main surface 600 to define a principal axis (A). Principal axis A and longitudinal axis LA form a bias angle (B) between them. In some embodiments, the bias angle B is in the range of approximately 0 to approximately 90 degrees, for example, in the range of approximately 20 to approximately 70 degrees.

[0137] In another embodiment, as shown in Figure 7, the first main surface 710 of the structured film 700 is characterized as an array of inverted pyramidal structures 720. The structures 720 include facets 722 that intersect at valleys (i.e., inverted peaks) 721, with opposing edges 724 of each facet forming the base of the pyramidal structure 720 (i.e., located on the outermost surface of the structured film 700), and the base of the pyramid is a polygon such as a square or rectangle. In this embodiment, adjacent rows (e.g., end row 762 and adjacent row 764) are offset from each other, and the valley bottoms of adjacent structures (e.g., 723 in row 762 and 725 in row 764) are at different positions in the longitudinal direction of the row (e.g., the y-axis). It is explicitly assumed that such offset arrangements are applicable to any of the structural shapes described herein.

[0138] Advantageously, in certain embodiments, the structure refracts light incident on the first principal surface of the wavelength-selective multilayer so that it exits the structured film at an angle closer to perpendicular than the angle of incidence (for example, in some cases, directed toward the polymer multilayer optical film at an angle closer to perpendicular to the first principal surface of the polymer multilayer optical film than the angle of incidence of the incident light).

[0139] In some cases, the structured film is flexible (as defined in the glossary). The advantage of using a flexible structured film is that it avoids the high costs associated with handling hard glass, especially small glass fragments. Small glass fragments are prone to breakage during handling, and bonding numerous fragments together requires considerable effort. Furthermore, in some embodiments of this disclosure, a flexible structured film is used in roll-to-roll processing in the manufacture of wavelength-selective multilayers. The advantage of roll-to-roll manufacturing is that it allows for the manufacture of wavelength-selective multilayers in large-area configurations. In some cases, the structured film (or wavelength-selective multilayer) has an area of ​​at least 50 square centimeters, and may have an area of ​​60, 70, 80, 90, 100, 1,000, or at least 10,000 square centimeters.

[0140] In any of the above embodiments, the structured film may be composed of a polymer material, such as a (co)polymer, or solely of such material. In some representative embodiments, the structured film may include polyethylene terephthalate (PET), crosslinkable silicone, cured polysiloxane, silicone thermoplastic polymer, cured urethane, thermoplastic urethane, cured (meth)acrylate, cured epoxy, cured vinyl ether, cured oxetane, cured thiol-acrylate, cured thiol-ene, polypropylene, polyethylene, PMMA, coPMMA, polyimide, cyclic olefin copolymer, cyclic olefin polymer, polycarbonate, polyethylene naphthalate (PEN), or a fluoropolymer (co)polymer containing polymerization units derived from one or more of tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxyalkylene, or vinyl fluoride, or a combination thereof. Optionally, any of the above cured polymer materials may be crosslinked.

[0141] Suitable polyimides are available under the "KAPTON" trademark of EI DuPont de Nemours (Wilmington, DE), with "KAPTON CS100" being currently preferred. Suitable PMMA polymers include CP71 and CP80 from Ineos Acrylics, Inc. (Wilmington, DE). An example of a suitable crosslinkable silicone is the "DOW CORNING 93-500 SPACE GRADE ENCAPSULANT KIT" trademark of Dow Corning Corporation (Midland, MI). An example of a suitable polycarbonate is the "Makrofol" trademark of Bayer AG (Darmstadt, Germany). Suitable methyl methacrylate copolymers (CoPMMAs) include, for example, CoPMMAs consisting of 75% by weight of methyl methacrylate (MMA) monomers and 25% by weight of ethyl acrylate (EA) monomers (available, for example, as "PERSPEX CP63" from Ineos Acrylics, Inc. (London, England) or "ATOGLAS 510" from Arkema Corp. (Philadelphia, PA)), CoPMMAs formed from MMA comonomer units and n-butyl methacrylate (nBMA) comonomer units, or blends of PMMA and poly(vinylidene fluoride) (PVDF). Suitable polyethylene naphthalate (PEN) polymers are available under the "Teonex Q51" trademark from DuPont Teijin (Chester, VA).

[0142] In certain representative embodiments, the fluorine-containing (co)polymer preferably includes tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, perfluoroalkoxyalkane, or a combination thereof. Suitable fluoropolymers are available under the trademark "TEFLON FEP100" of EI DuPont de Nemours (Wilmington, DE), with "TEFLON FEP100 500A" currently being preferred. Appropriate representative fluoropolymers also include copolymers (THVs) of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, available under the trademarks "DYNEON THV 220," "DYNEON THV 221," "DYNEON THV 230," "DYNEON THV 2030," "DYNEON THV 415," "DYNEON THV 500," "DYNEON THV 610," and "DYNEON THV 815" of Dyneon LLC (Oakdale, MN).

[0143] In certain applications, such as when the multilayer is exposed to large fluctuations in ambient temperature, it may be useful to use a film with a low coefficient of thermal expansion (CTE). Typical examples of low-CTE polymers include, but are not limited to, polyimide, heat-stabilized PEN, and PET. Preferably, the low-CTE material has a CTE of 80 ppm / K or less, 70 ppm / K, 60 ppm / K, 50 ppm / K, 40 ppm / K, 30 ppm / K, or even 25 ppm / K or less. The coefficient of thermal expansion has the general meaning used in this industry, i.e., the meaning measured according to ASTM E831.

[0144] The smoothness and adhesion of layers to the structured film can be improved by appropriate pretreatment or the application of any primer layer. Surface modification methods are known to those skilled in the art. In one embodiment, the pretreatment procedure includes electro-discharge pretreatment (e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge, or atmospheric pressure discharge) of the substrate in a reactive or inert atmosphere, chemical pretreatment, or flame pretreatment. These pretreatments help ensure that the subsequent layer is accepted on the structured film surface. In one embodiment, the method may include plasma pretreatment. Plasma pretreatment for organic surfaces may include nitrogen or water vapor. Another pretreatment procedure includes coating the structured film with an inorganic or organic base coat layer and optionally further applying one of the above pretreatments (e.g., plasma).

[0145] Preferably, the structured film itself transmits at least 70, 80, 90, or 95% on average of incident visible light in the wavelength range from 400 nm to 700 nm.

[0146] Any barrier layer In other embodiments, the wavelength-selective multilayer may include an optional barrier layer. For example, it may be located in the position of the intermediate layer 60 and / or 80 in Figure 1A, or in the position of the intermediate layer 60 in Figure 2C. The barrier layer 60 is located between the second main surface 38 of the inorganic multilayer optical film 30 and the first main surface 26 of the polymer multilayer optical film 20. If the wavelength-selective multilayer 10 includes a structured film 50, the barrier layer 60 is located between the first main surface 56 of the structured film 50 and the second main surface 38 of the inorganic multilayer optical film 30. The barrier layer 80 is located between the second main surface 28 of the polymer multilayer optical film 20 and the substrate 70 (for example, a solar cell array, which will be described in detail below).

[0147] Referring to Figure 1C, a schematic cross-sectional view of the barrier layer 90 is shown. The barrier layer 90 may consist of a single layer or multiple layers. In some embodiments, the barrier layer 90 includes an inorganic layer 92. Suitable inorganic layers include inorganic materials selected from silicon oxide, silicon alumina oxide, silicon oxynitride, gallium oxide, magnesium oxide, niobium oxide, titanium dioxide, yttrium oxide, zinc oxide, tin oxide, nickel oxide, tungsten oxide, aluminum-doped zinc oxide, indium tin oxide, zirconium oxide, zirconium oxynitride, hafnia, aluminum oxide, alumina-doped silicon oxide, lanthanum fluoride, neodymium fluoride, aluminum fluoride, magnesium fluoride, calcium fluoride, or combinations thereof.

[0148] In certain embodiments, the inorganic layer is a metal oxide layer. Typically, such metal oxide layers include titanium oxide, aluminum oxide, zinc oxide, tantalum pentoxide, zirconium oxide, or niobium oxide. In selected embodiments, the metal oxide layer includes titanium oxide. A suitable inorganic layer consists of a continuous thickness of 15 to 60 nm of one or more inorganic materials. Thus, the inorganic layer may be formed from a single metal oxide or from a combination of two or more metal oxides.

[0149] The thickness of the inorganic layer is often 15 nm or more, 17 nm, 20 nm, 22 nm, 25 nm, 27 nm, or 30 nm or more; and 60 nm or less, 57 nm, 55 nm, 52 nm, 50 nm, 47 nm, 45 nm, 42 nm, 40 nm, 37 nm, 35 nm, 32 nm, 30 nm, 27 nm, 25 nm, 22 nm, or 20 nm or less. In some cases, the thickness of the inorganic layer is 15-20 nm, 20-30 nm, or 20-40 nm. If the thickness is less than 15 nm, it is likely to become a discontinuous island structure of deposited inorganic material rather than a continuous film. If the thickness is too large, the inorganic layer may reduce visible light transmission or impart a visible color to the material.

[0150] Preferably, the inorganic layer does not impart a yellow appearance to the wavelength-selective multilayer. Whether or not an article has a yellow appearance can be determined, for example, by measuring the transmittance of light passing through the wavelength-selective multilayer. If the average transmittance is 70% or higher for light in the wavelength range above 410 nm at any of the incident angles of 0°, 30°, 45°, 60°, or 75°, the article is judged not to exhibit a yellow appearance. On the other hand, if the average transmittance is less than 70% under the same conditions, the article is likely to appear yellowish.

[0151] Inorganic layers can be manufactured by vapor deposition, reactive vapor deposition, sputtering, reactive sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or atomic layer deposition (ALD). Preferred methods include vacuum methods such as sputtering and vapor deposition. For example, one of two forms of physical vapor deposition (PVD), namely vapor deposition or sputtering, may be used. Vapor-deposited films are obtained by heating a coating material (evaporation source) to its evaporation temperature and then condensing the vapor onto a substrate. Among vapor deposition methods, electron beam deposition is the most commonly used. Sputtered films are formed by energetically impacting the surface of a material (target) with gas ions and condensing the ejected atoms onto a nearby substrate. The deposition rate and structure-properties of the thin film are greatly influenced by the deposition method and conditions used. Ideally, the deposition rate should be sufficiently high, and the process should be able to form a dense, low-stress, void-free film that exhibits little light absorption.

[0152] In some embodiments, the barrier layer 90 includes an inorganic layer 92 and a (e.g., first) (co)polymer layer 94 laminated thereon. The barrier layer 90 may further include a (e.g., second) (co)polymer layer 96 located on the opposite side of the first (co)polymer layer 94. Such a configuration yields a three-layer barrier layer 90 in which the inorganic layer 92 is positioned between the two (co)polymer layers 94, 96. Considering a barrier layer positioned in a wavelength-selective multilayer, the second (co)polymer layer is located between the inorganic layer and the first principal surface of the polymer multilayer optical film. In other words, referring to Figure 1A, the barrier layer 60 optionally includes a (co)polymer layer positioned adjacent to the first principal surface 26 of the polymer multilayer optical film 20.

[0153] Wavelength-selective multilayers containing a barrier layer provide protection from the atomic oxygen environment. For example, advantageously, in many cases, wavelength-selective multilayers exhibit a performance of 1 × 10⁻¹⁶ in atomic oxygen degradation tests. -20 mg / atom, 1 x 10 -21 mg / atom, or 1 × 10 -22 This indicates an atomic oxygen degradation rate of less than mg / atom. Such atomic oxygen degradation resistance is particularly useful when the light shielding material is part of a Low Earth Orbit (LEO) satellite instrument.

[0154] Barrier layers according to at least some embodiments of this disclosure can exhibit excellent mechanical properties such as elasticity and flexibility while still having a low atomic oxygen degradation rate.

[0155] Any (co)polymer layer in the barrier layer includes a (co)polymer selected from olefin-based (co)polymers, (meth)acrylate-based (co)polymers, urethane-based (co)polymers, fluoropolymers, silicone-based (co)polymers, or combinations thereof. The (co)polymer layer can be formed by various processes using a variety of organic materials or compounds. The (co)polymer layer may be crosslinked in situ after coating. In one embodiment, the (co)polymer layer can be formed by flash evaporation, vapor deposition, and (co)polymerization of monomers, for example using heat, plasma, ultraviolet light, or electron beams.

[0156] Typical monomers used in such methods include volatile (meth)acrylate monomers. In certain embodiments, volatile acrylate monomers are used. A suitable (meth)acrylate has a molecular weight low enough to allow flash evaporation and a molecular weight high enough to allow condensation on a substrate. These organic materials or compounds can also be vaporized by methods such as those described in PCT Publication WO2022 / 243756 (Sweetnam et al.) concerning the evaporation of metal alkoxides.

[0157] If necessary, one or more (co)polymer layers may be applied using conventional methods such as plasma deposition, solution coating, extrusion coating, roll coating (e.g., gravure roll coating), or spray coating (e.g., electrostatic spray coating), and may be crosslinked or (co)polymerized as needed (e.g., as described above). The desired chemical composition and thickness of the additional layers depend in part on the properties of the wavelength-selective multilayer and the desired application. Coating efficiency can be improved by cooling the article.

[0158] Representative organic compounds include esters, vinyl compounds, alcohols, carboxylic acids, acid anhydrides, acyl halides, thiols, amines, and mixtures thereof. Non-limiting examples of esters include (meth)acrylates, which can be used alone or in combination with other polyfunctional or monofunctional (meth)acrylates. Representative (meth)acrylates include hexanediol diacrylate, ethoxyethyl acrylate, phenoxyethyl acrylate, cyanoethyl (mono)acrylate, isobornyl acrylate, octadecyl acrylate, isodecyl acrylate, lauryl acrylate, β-carboxyethyl acrylate, tetrahydrofurfuryl acrylate, dinitrile acrylate, pentafluorophenyl acrylate, nitrophenyl acrylate, 2-phenoxyethyl acrylate, 2,2,2-trifluoromethyl acrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, and tripropylene Examples include glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, polyethylene glycol diacrylate, tetraethylene glycol diacrylate, bisphenol A epoxy diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propylated trimethylolpropane triacrylate, tris(2-hydroxyethyl)-isocyanurate triacrylate, pentaerythritol triacrylate, phenylthioethyl acrylate, naphthyloxyethyl acrylate, UCB Chemicals' IRR-214 cyclic diacrylate, Rad-Cure Corporation's epoxy acrylate RDX80095, methacrylates corresponding to the above acrylates, and mixtures thereof. Typical vinyl compounds include vinyl ethers, styrene, vinylnaphthylene, and acrylonitrile. Typical alcohols include hexanediol, naphthalenediol, and hydroxyethyl methacrylate. Typical carboxylic acids include phthalic acid and terephthalic acid ((meth)acrylic acid).Typical acid anhydrides include phthalic anhydride and glutaric anhydride. Typical acyl halides include hexanedioxide dichloride and succinic acid dichloride. Typical thiols include ethylene glycol bisthioglycolate and phenylthioethyl acrylate. Typical amines include ethylenediamine and hexane-1,6-diamine.

[0159] Optionally, if the barrier layer contains at least one (co)polymer layer, the (co)polymer layer may further contain additives consisting of a UV absorber, a hindered amine light stabilizer, an antioxidant, or a combination thereof. UV absorbers (UVA), hindered amine light stabilizers (HALS), and antioxidants can contribute to preventing photo-oxidative degradation of the (co)polymer layer. Suitable compounds include benzophenone-based, benzotriazole-based, and triazine-based compounds (e.g., benzotriazine-based). Representative UVA compounds for incorporation into the (co)polymer layer include BASF Corporation (Florham Park, NJ) trademarks "TINUVIN 1577" and "TINUVIN 1600". Representative UVA oligomers compatible with PVDF fluoropolymers are described in U.S. Patent No. 9,670,300 (Olson et al.) and U.S. Patent Publication No. 2017 / 0198129 (Olson et al.). Typical HALS incorporated into the (co)polymer layer include BASF Corporation's trademarks "CHIMMASORB 944" and "TINUVIN 123". Typically, UVA, HALS, and / or antioxidants are incorporated into the (co)polymer layer at a concentration of 1 to 10% by weight.

[0160] If a first (co)polymer layer is present, the layer is preferably crosslinked. In some representative embodiments, the first (co)polymer layer includes olefin-based (co)polymers selected from low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate, polyethylene-methyl acrylate, polyethylene-octene, polyethylene-propylene, polyethylene-butene, polyethylene-maleic anhydride, polymethylpentene, polyisobutene, polyisobutylene, polyethylene-propylene-diene, cyclic olefin (co)polymers, and blends thereof.

[0161] In certain representative embodiments, at least one arbitrary (co)polymer layer further comprises a UV absorber, a hindered amine light stabilizer, an antioxidant, or a combination thereof. The UV absorber is preferably selected from benzotriazole compounds, benzophenone compounds, triazine compounds, or a combination thereof. Currently preferred hindered amine light stabilizers are available under the trademark "TINUVIN" of BASF USA (Florham Park, NJ). The hindered amine light stabilizers are preferably selected from TINUVIN 123, TINUVIN 144, TINUVIN 292, or a combination thereof. Currently preferred antioxidants are available under the trademarks "IRGANOX" and "IRGAFOS" of BASF. Antioxidants suitable for polyolefins are preferably selected from IRGANOX 1010, IRGANOX 1076, IRGAFOS 168, or a combination thereof.

[0162] Any barrier layer can be subjected to various post-treatments, such as heat treatment, UV or vacuum UV (VUV) treatment, or plasma treatment. Heat treatment can be carried out by passing the barrier layer through an oven or by directly heating the barrier layer in a coating apparatus (e.g., by using an infrared heater or by direct heating on a drum). Heat treatment may be carried out at temperatures, for example, about 30°C to about 200°C, about 35°C to about 150°C, or about 40°C to about 70°C.

[0163] Solar cell array In a second embodiment, a solar cell array is provided, which includes a wavelength-selective multilayer according to any embodiment of the first embodiment, the multilayer being arranged on the outer surface of the solar cell array.

[0164] Currently, one of the most promising energy resources is sunlight. The use of sunlight can be achieved through photovoltaic solar cells (also called PV cells or solar cells), which are used to photovoltaically convert sunlight into electric current. Solar cells are relatively small and are typically combined into a solar cell module (or PV module), which has a greater power output than individual solar cells. A solar cell module generally consists of two or more solar cells connected in a "string" configuration, surrounded by a encapsulant and further sealed by front and back panels, with at least one panel being translucent to sunlight.

[0165] Therefore, the wavelength-selective multilayer of this disclosure can be used to protect the solar cell array by being incorporated on the outer surface of the solar cell array.

[0166] Referring again to Figure 1A, this disclosure describes a solar cell array 40 in which a wavelength-selective multilayer 10 is disposed on the outer surface 76 of a solar cell array 70. The wavelength-selective multilayer 10 comprises an inorganic multilayer optical film 30 and a polymer multilayer optical film 20. In some cases, the wavelength-selective multilayer 10 may be directly bonded to the surface 76 of the solar cell array 70, for example, by thermal lamination. Alternatively, one or more optional intermediate layers 80 may be present between the wavelength-selective multilayer 10 and the solar cell array surface 76, including a barrier layer, a transparent adhesive bonding layer, or a encapsulant. If an intermediate layer 80 is present, in some embodiments, the intermediate layer 80 is a barrier layer according to one of the embodiments described in detail in relation to the first aspect above. In such cases, the solar cell array 40 further includes a barrier layer 80 disposed between the solar cell array 70 and the wavelength-selective multilayer 10.

[0167] List of examples

[0168] As a first embodiment, a wavelength-selective multilayer is provided. The wavelength-selective multilayer includes a polymer multilayer optical film having a first principal surface and a second principal surface opposite to it. The polymer multilayer optical film has one or more alternating first and second polymer optical layers, which together reflect at least 50, 60, 70, 80, 90, or 95 percent on average of the light incident normal to the first principal surface of the wavelength-selective multilayer over a wavelength reflection bandwidth of at least 30 nanometers. The wavelength range is 800 nanometers (nm) to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm. Furthermore, the wavelength-selective multilayer includes an inorganic multilayer optical film having a first principal surface and a second principal surface opposite it, the second principal surface of the inorganic multilayer optical film being bonded to the first principal surface of the polymer multilayer optical film. The inorganic multilayer optical film has one or more alternating first and second inorganic optical layers, which together reflect and absorb at least 50, 60, 70, 80, 90, or 95 percent of ultraviolet light, on average, of the light incident normal to the first principal surface of the wavelength-selective multilayer, over a wavelength bandwidth of at least 30 nanometers. The wavelength range is 190 nm to 400 nm.

[0169] As a second embodiment, a wavelength-selective multilayer according to the first embodiment is provided, further comprising a structured film. The structured film has a first principal surface and an opposing second principal surface, the first principal surface having a plurality of protruding structures. At least a portion of the plurality of structures have a surface inclination such that light normal to the first principal surface of the structured film strikes the first principal surface or the surface of at least one other structure after reflection. The structured film is positioned (a) between the first principal surface of a polymer multilayer optical film and the second principal surface of an inorganic multilayer optical film, or (b) adjacent to the second principal surface of the polymer multilayer optical film opposite to the inorganic multilayer optical film.

[0170] As a third embodiment, a wavelength-selective multilayer according to the first or second embodiment is provided, wherein at least a portion of the plurality of structures has at least one inclined sidewall having an apex angle of 90 degrees or less, the apex angle being 5 degrees, 15 degrees, 25 degrees, 35 degrees, or 45 degrees or more.

[0171] As a fourth embodiment, a wavelength-selective multilayer according to the second or third embodiment is provided, wherein at least a portion of the structure has a triangular cross-sectional shape.

[0172] As a fifth embodiment, a wavelength-selective multilayer according to any of the second to fourth embodiments is provided, the structure having the shape of a prism, pyramid, inverted pyramid, diffraction grating, inverted cone, or cone.

[0173] As a sixth embodiment, a wavelength-selective multilayer according to any of the second to fifth embodiments is provided, wherein the structured film is flexible.

[0174] As a seventh embodiment, a wavelength-selective multilayer according to any of the second to sixth embodiments is provided, wherein the structure refracts light incident on the first principal surface of the wavelength-selective multilayer at an angle other than the normal, and the exit angle is set to an angle closer to the normal than the incident angle.

[0175] As an eighth embodiment, a wavelength-selective multilayer according to any of the first to seventh embodiments is provided, which further includes a barrier layer disposed between a second main surface of an inorganic multilayer optical film and a first main surface of a polymer multilayer optical film.

[0176] As a ninth embodiment, a wavelength-selective multilayer according to the eighth embodiment is provided, wherein the structured film is located between the first main surface of the polymer multilayer optical film and the second main surface of the inorganic multilayer optical film, and the barrier layer is located between the first main surface of the structured film and the second main surface of the inorganic multilayer optical film.

[0177] As a tenth embodiment, a wavelength-selective multilayer according to the eighth or ninth embodiment is provided, wherein the barrier layer includes an inorganic layer.

[0178] As an eleventh embodiment, a wavelength-selective multilayer according to the tenth embodiment is provided, wherein the thickness of the inorganic layer is 15 to 60 nm.

[0179] As a twelfth embodiment, a wavelength-selective multilayer according to any eighth to eleventh embodiment is provided, wherein the barrier layer further comprises a (co)polymer layer laminated on an inorganic layer.

[0180] As a thirteenth embodiment, a wavelength-selective multilayer according to the twelfth embodiment is provided, wherein the barrier layer further includes a (co)polymer layer disposed between the inorganic layer and the first main surface of the polymer multilayer optical film.

[0181] As a fourteenth embodiment, a wavelength-selective multilayer according to any of the first to thirteenth embodiments is provided, the polymer multilayer optical film further comprising a third polymer optical layer disposed between at least one pair of alternately laminated first and second polymer optical layers.

[0182] As a 15th embodiment, a wavelength-selective multilayer according to any of the 1st to 14th embodiments is provided, the wavelength-selective multilayer having an average transmittance of 50, 60, 70, 80, 90, or 95 percent or more with respect to normally incident light. The wavelength range is from 400 nm to 700 nm, from 400 nm to 1100 nm, or from 400 nm to 1350 nm.

[0183] As a sixteenth embodiment, a wavelength-selective multilayer according to any of the first to fifteenth embodiments is provided, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide, titanium oxide, silicon oxynitride, molybdenum oxide, tungsten oxide, silicon nitride, indium tin oxide, hafnium oxide, tantalum oxide, zirconium oxynitride, zirconium oxide, aluminum zinc oxide, or zinc oxide, and the second optical layer comprises at least one of silicon oxide, silicon alumina oxide, N-type or P-type doped silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, indium tin oxide, or zinc oxide.

[0184] As a 17th embodiment, a wavelength-selective multilayer according to any 1 to 16th embodiment is provided, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and the second optical layer comprises silicon alumina oxide.

[0185] As an 18th embodiment, a wavelength-selective multilayer according to any of the 1st to 17th embodiments is provided, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and the second optical layer comprises silicon oxide.

[0186] As a 19th embodiment, a wavelength-selective multilayer according to any of the 1st to 18th embodiments is provided, wherein the average transmittance when light in the wavelength range of 400 nm to 700 nm, 400 nm to 1100 nm, or 400 nm to 1350 nm is passed through decreases by less than 20%, less than 10%, less than 5%, or less than 1% after exposure to a specific amount of ultraviolet irradiation.

[0187] As a 20th embodiment, a wavelength-selective multilayer according to any of the 1st to 19th embodiments is provided, wherein the average reflectance when reflecting light in the wavelength range of 800nm ​​to 1200nm, 1200nm to 1600nm, or 800nm ​​to 1600nm decreases by less than 20%, less than 10%, less than 5%, or less than 1% after exposure to a specific amount of ultraviolet irradiation.

[0188] As a 21st embodiment, a wavelength-selective multilayer according to any of the 1st to 20th embodiments is provided, wherein the polymer multilayer optical film has a third harmonic and reflects at least 80, 90, or 95 percent of the light incident normal to the first principal surface of the wavelength-selective multilayer in the wavelength ranges of 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm over a wavelength bandwidth of at least 30 nm.

[0189] As a 22nd embodiment, a solar cell array is provided. The solar cell array includes a wavelength-selective multilayer according to any of the first to 21 embodiments, the multilayer being arranged on the outer surface of the solar cell array.

[0190] As a 23rd embodiment, a solar cell array according to the 22nd embodiment is provided, which further includes a barrier layer disposed between the solar cell array and a wavelength-selective multilayer.

[0191] Examples Unless otherwise stated or made clear from the context, all parts, percentages, ratios, etc., in the examples and other parts of this specification are based on mass (weight). Materials used in the examples [Table 1]

[0192] Test method Spectral Properties Modeling Test: Before manufacturing the structured UV shield, the optical properties (transmission, reflection, and absorption) of the desired inorganic multilayer optical film coating were modeled to accurately determine the required film thickness of the optical coating layer. To perform this modeling, test samples 1 and 2 were measured using an ellipsometer (product name "RC2 Ellipsometer," manufactured by JA Woolam, Lincoln, Nebraska) to determine the spectral refractive index (n) and extinction coefficient (k) of the deposited TiO2 and SiO2 samples. Next, the n and k values ​​obtained above were entered into optical modeling software (product name "Essential MacLeod," manufactured by The Thin Film Center, Tucson, Arizona) to calculate the reflection, transmission, and absorption spectra of the inorganic multilayer optical films described in the "Comparative Examples Structure Table," "Example Structure Table," and "Prophetic Example Structure Table" below. All structures were modeled using polyethylene terephthalate (PET) substrates, except for Comparative Example 4, which was modeled using a glass substrate. Comparative Examples 2 and 4, and Examples 1 and 2 were modeled using normal incident light, while Examples 3 and 4, and Predictive Examples 5, 6, and 7 were modeled using light with an incident angle of 45 degrees.

[0193] The overall transmittance, reflectance, and absorption spectra of Predicted Examples 5 and 6 were modeled by the following method. First, the spectra of the inorganic multilayer optical films were modeled according to the method described in the previous paragraph. Next, the measured spectra of the film of Comparative Example 1 were obtained. These Predicted Examples have structured inorganic multilayer optical films and structured polymer multilayer optical films, and it is assumed that incident light reflected by these structures is re-entered on the second surface of the film. Therefore, it was necessary to model the effect of light passing through the film twice. The total transmittance, reflectance, and absorption after light has passed through the film twice were calculated using the following formulas (all in units of %).

number

[0194] Here, R total / T total / A total R represents the total effective reflectance / transmittance / absorptance of light after it has passed through the film twice. R1 represents the reflected light after a single reflection from the film surface. in / T in / A in This indicates the reflectance / transmittance / absorptance of an inorganic vapor-coated mirror, and R p / T p / A p This indicates the reflectance / transmittance / absorption of a polymeric multilayer optical film.

[0195] The overall transmittance, reflectance, and absorption spectrum of Prophetic Example 7 were modeled using the following method. First, the spectrum of the inorganic multilayer optical film coating was modeled according to the method described above. Next, the spectrum of the third-harmonic multilayer optical mirror film that reflects infrared light was calculated based on Figure 12 of U.S. Patent No. 6,744,561 (Condo et al.). In this calculation, it was assumed that there is no absorption of light in the wavelength range above 360 ​​nm, and that 100% of the light is absorbed in the wavelength range below 360 nm. This was used as an approximation of the absorption characteristics of polyethylene terephthalate (PET) and polyethylene-co-octene (poly(ethylene-co-octene), PE-PO). The film of Prophetic Example 7 has a structured inorganic multilayer optical film, and is configured so that incident light generated by reflection from the film strikes other surfaces of the film again. Therefore, it was necessary to model the effect of "second reflection" of light reflected by the inorganic multilayer optical film. The total transmittance, reflectance, and absorptance after passing through the film were calculated using the following formula (all units are in %):

number

[0196] Please note that all these values ​​are spectrally resolved quantities. However, in the results table below, these values ​​are reported as average quantities over the selected wavelength range.

[0197] Spectroscopic characteristic measurement test: For freestanding examples of ultraviolet shielding materials, spectral transmittance and reflectance were measured using a spectrophotometer (product name "LAMBDA 1050," PerkinElmer, Inc., Waltham, Massachusetts). Absorption was calculated in percentage units using the following formula: Absorption (%) = 100 - Reflectance - Transmittance. The measured spectral reflectance, absorptiveness, and transmittance were reported as average values ​​(percentages) in their respective wavelength ranges in the following tables: Infrared Reflection Results Table, Ultraviolet Reflection and Absorption Results Table, and Transmission Results Table.

[0198] Solar exposure test: The samples were exposed using a xenon arc lamp as the light source and a Weather-Ometer (trade name "Atlas Ci5000," AMETEK, Berwin, Pennsylvania) equipped with internal and external quartz filters. This quartz filter set minimizes attenuation to the xenon lamp's spectral power distribution, approximately replicating the shape of solar power (ASTM E490). To increase the rate of dose accumulation, the samples were placed on custom-made stainless steel and aluminum extension holders. These extension holders moved the irradiation surface from 19 inches (48.3 cm) to 13.5 inches (34.3 cm) from the lamp core. The irradiance was 1.5 W / m² at 340 nm on the rack surface. 2 Controlled to the extent that, on the extended sample surface, 2.6 W / m at 340 nm.2 The following measurements were taken: The ambient air temperature inside the Weather-Ometer was controlled to 48°C, the blackboard thermometer (BPT) was controlled to 75°C on the rack surface, and approximately 95°C on the sample surface. Relative humidity was controlled to 30%. The sample was exposed without backing. The sample had a total cumulative irradiance of 470 MJ / m² in the wavelength range of 250–385 nm. 2 They were exposed to the above doses.

[0199] The decrease in the spectral properties of the sample after solar exposure was calculated using the following formula.

number

[0200] Here, S fresh This indicates the average value of a specific spectrum (e.g., transmittance or reflectance) before solar exposure in a given wavelength range (e.g., 400-700 nm), and S age The values ​​shown represent the average spectral values ​​in the same wavelength range after the above exposure. The results of the Solar Aging Test are summarized in the "Solar Aging Results Tables".

[0201] Flexibility test: The flexibility of the sample was evaluated by wrapping the film around a metal mandrel (0.5 inches (1.27 cm) in diameter). The coated side was positioned facing outwards from the mandrel. Spectral properties tests were performed both before and after wrapping the film around the mandrel. The change in spectral values ​​was calculated as a percentage of the absolute value using the following formula.

number

[0202] Here, S unwrapped and S wrappedThe values ​​shown represent the average values ​​of specific spectra (e.g., transmittance, reflectance, or absorptance) for the same sample before and after winding. These values ​​are calculated as percentages of the average values ​​within a given wavelength range (e.g., 400-700 nm). This calculation was performed individually for the transmission spectrum, reflectance spectrum, and absorption spectrum. The calculated percentage difference in the spectrum after winding is shown in the "Flexibility Test Results Table" below.

[0203] Test sample Test Sample 1: A 70 nm thick TiO2 layer was deposited on a silicon chip using the following method. The deposition apparatus used was an Optical Coater manufactured by Denton Vacuum, equipped with a 5-planetary drive system located approximately 30 inches (76.2 cm) above a 4-pocket Temescal electron beam gun (manufactured by Ferro Tec Corporation, Livermore, California). This planetary system is designed to hold the substrate perpendicular to the evaporation source and cause it to undergo circular motion (planetary motion) in and out of the evaporation plume during deposition. The actual procedure for the deposition process was as follows: a) The vacuum chamber of the deposition apparatus was vented to atmospheric pressure, and one of the five planets was removed. The substrate was secured to the planet using polyimide tape and prepared for deposition. b) The planet was reattached, and the other four planets were configured similarly as needed, and then placed back into the coater. c) The chamber was closed, and the vacuum level was set to 2 × 10⁻⁶. -5 Torr(2.7×10 -3 The system was evacuated until the pressure was less than Pa. d) After the vacuum had sufficiently decreased, an ion beam treatment was performed using a Kaufman-type ion source at a voltage of 400V for approximately 10 minutes as a pretreatment to improve adhesion to the substrate. e) Oxygen gas was introduced via an MKS mass flow controller (MKS Instruments, Inc., Andover, Massachusetts) and the pressure was set to 4.0 × 10⁻⁶ -5Torr(5.3×10 -3 The pressure was adjusted to Pa. The amount of oxygen introduced was typically about 10 standard cubic centimeters (sccm) per minute. f) The planetary system was started and rotated at a speed of about 60 rpm to ensure high uniformity of film deposition across the entire substrate. g) The Temescal electron beam gun was powered on. A voltage of 10 kV and a current of several mA were applied to the filament to heat the source material of the electron beam gun. Heating of the source and control of the film deposition rate were performed using an Optical Monitoring System (OMS) manufactured by Eddy Company (Apple Valley, California). Heating was continued until the source material reached the desired deposition rate. The deposition rate was set to 2 Å / sec (A / s) for TiO2 and 4 Å / sec (A / s) for SiO2. Once the desired deposition rate was reached and stabilized, the shutter separating the source and the planet was opened, and film deposition was carried out while controlling the deposition rate with the OMS until the desired optical film thickness was reached. After the target film thickness was reached, the shutter was closed, and the OMS stopped supplying power to the electron beam source. h) The main power was shut off and the source was allowed to cool for approximately 10 minutes. i) The same process was repeated for other layers or different materials as needed until the desired multilayer optical film was obtained. j) The chamber was then vented to atmospheric pressure with nitrogen gas (N2), and each planet was removed to recover the substrate.

[0204] Test sample 2: A 115 nm thick SiO2 layer was deposited on a silicon chip using the same method as in test sample 1.

[0205] Comparative Example 1: An infrared (IR) reflective multilayer optical mirror film was fabricated with an alternating layer configuration ABCB. Here, optical layer A was made of PET resin, optical layer B of PETG resin, and optical layer C of CoPMMA resin. A typical optical film having an ABCB layer configuration is described in U.S. Patent No. 6,667,095 (Wheatley et al.), which is incorporated herein by reference. This film was fabricated by co-extrusion and biaxial stretching according to the method described in U.S. Published Patent Publication No. 2001 / 0013668 (Neavin et al.), with the following exceptions: PET, PETG, and CoPMMA were co-extruded through a multilayer polymer melt manifold to form a stack of 425 optical layers. The optical layer thickness profile of this IR reflective mirror film was designed to have a generally linear thickness distribution adjusted to reflect light in the 1200 nm to 1800 nm range. The layer thickness profiles of this type of film can be adjusted to improve spectral characteristics by combining them with layer profile information obtained by microscopy using an axial rod apparatus disclosed in U.S. Patent No. 6,783,349 (Neavin et al.). In addition to these optical layers, a non-optical protective boundary layer (PET) was co-extruded on both sides of the optical layer stack. The multilayer molten material was cast onto chill rolls through a film die according to the general method for manufacturing polyester films and cooled and solidified. The cast web was stretched using a commercial-scale twin-screw tenter machine to a profile similar to the temperature and stretching conditions described in Neavin et al. (2001 / 0013668).

[0206] Comparative Example 2: A vapor-deposited multilayer optical film was prepared using the same method as in Test Sample 1, but with the difference being the use of a PET film as the substrate. The structure deposited on the PET film substrate is summarized in the "Comparative Examples Structure Table" below. The PET film substrates used in these samples had one side pre-treated by the supplier to improve adhesion with other materials. In the vapor deposition process, the substrate was fixed to the planet with tape so that the untreated side would be coated.

[0207] Comparative Example 3: Comparative Example 3 was a piece of BEF4 film.

[0208] Comparative Example 4: Comparative Example 4 was prepared using the same method as Comparative Example 2, but differed in that BK7 glass was used as the substrate. The deposited coating layer is as shown in the "Comparative Examples Structure Table".

[0209] Preparation Example 1: A piece of the infrared mirror film substrate from Comparative Example 1 was covered with a laminate of a base polymer layer (layer 1), an inorganic silicon alumina oxide (SiAlOx) barrier layer (layer 2), and a protective polymer layer (layer 3), and the film was formed in a vacuum coater. The coater used had a structure similar to that described in U.S. Patent No. 5,440,446 (Shaw et al.) and U.S. Patent No. 7,018,713 (Padiyath et al.), and the contents of both patents are incorporated herein by reference. The method for forming each layer is as follows.

[0210] Layer 1 (base polymer layer): A sheet of Comparative Example 1 infrared mirror film, measuring 300 mm x 300 mm, was fixed with tape to the surface of a 356 mm wide PET film roll (long length). To ensure stable operation of the film deposition apparatus, at least 150 feet (approximately 46 m) of unsampled areas were provided before and after the sheet sample to absorb the transient regions of heating and cooling. This film roll was loaded into a roll-to-roll type vacuum processing chamber and subjected to a pressure of 2 × 10⁻¹⁰ -5The vacuum was evacuated to Torr. The web speed was maintained at 3.4 m / min, and the back side of the film was placed in close contact with a coating drum cooled to -10°C. With the back side in contact with the drum, the surface was pretreated by irradiating it with nitrogen plasma (0.02 kW). Subsequently, monomer SR833S was deposited on the microstructure surface of the sample. The monomer was degassed under vacuum (20 mTorr) and supplied at a flow rate of 0.89 mL / min by syringe pump, and introduced into a heated vaporization chamber maintained at a temperature of 260°C along with 60 sccm of nitrogen carrier gas. The vaporized monomer stream condensed on the film surface, and a crosslinking reaction was carried out using a 7.0 kV, 4 mA multi-filament electron beam cure gun to form a 500 nm thick substrate polymer layer.

[0211] Layer 2 (Inorganic Layer): Immediately after deposition of the base polymer layer, and while the back surface remained in contact with the drum, a SiAlOx layer was deposited by sputtering. Two AC (40kHz) power supplies were used to control cathode pairs, each containing two 90% Si / 10% Al sputtering targets. The voltage signals from each power supply were input to a proportional-integral-derivative (PID) control loop to maintain a constant oxygen flow rate to each cathode. The sputtering conditions were as follows: AC power 16kW, gas mixture ratio Ar 350sccm / O 2 13sccm, sputtering pressure 3.5mTorr. This formed a 25nm thick SiAlOx layer on top of the base polymer layer (Layer 1).

[0212] Layer 3 (protective polymer layer): Immediately after deposition of the SiAlOx layer, the second acrylate layer was applied and crosslinked while the film remained in contact with the drum. The general conditions were the same as for layer 1, but the following changes were made: (1) The electron beam crosslinking conditions were set to 7kV and 10mA. (2) The monomer flow rate was increased to 1.33mL / min to form an acrylate layer with a thickness of 750nm. In addition, 3% by mass of DYNASYLAN 1189 was added to the protective polymer layer, with the remainder being SR833S.

[0213] Preparation Example 2: Preparation Example 2 is a linear prism microstructure film made of THV815, which was fabricated using the following procedure. A BEF4 microstructure film was obtained as the mold, and a three-roll vertical stack molding apparatus described in U.S. Patent Application Publication No. 2015 / 9108349 (Clarke et al.) was used. This apparatus has an extruder and an extrusion die, and has a structure that extrudes molten thermoplastic material onto the mold (in this case, the BEF4 tooling film) for transfer molding. The BEF4 film is wound around a cylindrical roll to form the desired surface pattern, which is transferred as the molten resin passes over this cylindrical surface. The casting roll temperature was 76.6°C, the roll speed was 18.8 m / min, and the pressure was 7600 pounds (300 pounds per inch). This resulted in a THV815 linear prism microstructure film with a thickness of 2 mil (approximately 50 μm). Its shape characteristics are shown in the "Prismatic THV815 Structure Table" below.

[0214] Preparation Example 3: This example was prepared using the same method as Comparative Example 2, but differed in that it used the prism-shaped THV815 film from Preparation Example 2 as the substrate. The structure of the vapor-deposited layer is summarized in the "Preparatory Examples Structure Table". The prism-shaped THV815 film substrate was fixed to the planet with tape with the structural side (uneven surface) facing upwards, and this became the vapor-deposited coating surface.

[0215] In vapor deposition on microstructured substrates, the substrate's geometry is a crucial factor. The inclination of the structural surface increases the surface area compared to a flat substrate; therefore, under the same deposition conditions, the film thickness on the microstructured substrate will be thinner. In other words, since a fixed volume of material is supplied during the deposition process, the film thickness per unit area decreases on substrates with a large surface area (film thickness = deposition volume / substrate surface area).

[0216] Therefore, in order to obtain the desired film thickness on a microstructured substrate, it is necessary to increase the deposition amount relative to the planar substrate. The coefficient of increase is equal to the ratio of the surface area of ​​the microstructured substrate to that of the planar substrate. In the case of a prism-shaped THV815 substrate (one-dimensional prism structure, apex angle 90°, inclination angle 45°), the required deposition volume increase coefficient is 1 / sin(peak angle / 2) = 1 / sin(45°) = 1.414.

[0217] Preparation Example 4: Using the prism-shaped THV815 film from Preparation Example 2, a base polymer layer (layer 1), a SiAlOx inorganic barrier layer (layer 2), and a protective polymer layer (layer 3) were formed in the same manner as in Preparation Example 1. However, the layer thicknesses were 360 ​​nm / 18 nm / 536 nm, respectively.

[0218] The obtained sheet sample was removed from the PET film roll, and a vapor-deposited multilayer optical film was formed on its protective polymer layer (layer 3) using the same method as in Preparation Example 3. The structure of the deposited coating layer is as described in the "Preparatory Examples Structure Table".

[0219] example

[0220] Example 1: The same method as in Comparative Example 2 was used, but instead of the PET film, the IR mirror film from Comparative Example 1 was used as the substrate. The structure of the deposited coating layer is shown in the "Examples Structure Table".

[0221] Example 2: The same method as in Comparative Example 2 was used, but instead of the PET film, Preparation Example 1 was used as the substrate. The structure of the deposited coating layer is shown in the Example Structure Table.

[0222] Example 3: One piece from Preparation Example 3 was superimposed on one piece from Comparative Example 1 to create the material. The structure of the deposited coating layer is as described in the Example Structure Table.

[0223] Example 4: One piece of Preparatory Example 4 was placed on top of one piece of Comparative Example 1 to prepare the sample. The structure of the deposited coating layer is as described in the Example Structure Table.

[0224] Proposed Example 5: A macrostructured version of Example 2 can be manufactured by multiple macrostructure methods. As an example, first, the film of Comparative Example 1 is thermoformed to form a desired shape having a one-dimensional prism-like structure (triangular cross-section with an apex angle of 90° and a height of 12 μm). Then, a laminate of a base polymer layer (layer 1) / inorganic SiAlOx barrier layer (layer 2) / protective polymer layer (layer 3) is formed on this macrostructured film in the same manner as in Preparation Example 4, and a vapor-deposited multilayer optical film is deposited on top of that in the same manner as in Preparation Example 4. In these macrostructured films, it is necessary to optimize the vapor-deposited layer considering that the incident light is not in the normal direction. The theoretically assumed deposition layer configuration is shown in the "Prophetic Examples Structure Table".

[0225] Predicted Example 6: A macrostructured version of Example 1 can be fabricated using multiple macrostructure formation methods. One example of a manufacturing method follows the procedure of Predicted Example 5, but differs in that the deposition of the base polymer layer, SiAlOx barrier layer, and protective polymer layer is omitted. The theoretically assumed deposition layer configuration is as shown in the Predicted Example Structure Table.

[0226] Predicted Example 7: This is a version having optical properties similar to Example 4, but with the addition of a third-order harmonic reflection band to achieve high reflectivity in specific wavelength bands. Specifically, it is a structure that reflects 80%, 90%, or 95% or more of light in a bandwidth of at least 30 nm in the range of 340-400 nm, 350-400 nm, or 365-400 nm, of light incident perpendicularly to the first main surface of the wavelength-selective multilayer. To achieve this, the IR reflective multilayer optical mirror film of Comparative Example 1 used in Example 4 is replaced with an IR reflective mirror film having a third-order harmonic reflection band. A suitable example is the "Example 16" IR film described in U.S. Patent No. 6,744,561 (Condo et al.) (composed of PET and polyethylene-co-octene (PE-PO)). This film has the characteristic that its primary reflection band reflects 90-99% of light in the 1020-1200nm range, and its third harmonic reflection band reflects 80-95% of light in the 340-400nm range. The transmittance, reflectance, and absorptance of this film were calculated based on the spectrum in Figure 12 (FIG. 12) of the Condo patent, assuming that reflectance (%) = 100 - transmittance (%) in the 360-1500nm range, and that the PET component completely absorbs light below 360nm. This assumption is valid because PET and PE-PO absorb strongly below 340nm and hardly absorb above 360nm. The optical properties of the predicted Example 7 were calculated by modeling the optical structure of Example 4 on the "Example 16" film described above, and considering the effect of secondary reflection due to the film surface structure. The results are shown in the table below. Comparative example structure table [Table 2] Preparation example structure table [Table 3] Example Structure Table [Table 4] Predicted Example Structure Table [Table 5] Infrared reflection result table [Table 6] Ultraviolet Reflection and Absorption Results Table [Table 7] Transmission result table [Table 8] Flexibility Test Results Table [Table 9]

[0227] Predicted Examples 5-7: These examples are similar in structure to Examples 1-4 and are therefore expected to exhibit similar behavior in bending tests. The only major difference between the two is that the polymer multilayer optical film substrate is macrostructured, and this macrostructure is not expected to have a substantial effect on the response to bending tests. Solar Weather Resistance Test Report [Table 10] [Table 11]

[0228] Predicted Examples 5-7: These examples are expected to exhibit similar behavior to Examples 1-4 in the Solar Aging Test. This is because the dominant factor influencing the test results is the composition of the polymer multilayer optical film used as the substrate. In Predicted Examples 5 and 6, since the substrate polymer multilayer optical film is the same as that used in Examples 1-4, it is not expected that there will be any difference in performance in the Solar Aging Test. In Predicted Example 7, PETG and CoPMMA in the substrate polymer multilayer optical film are replaced with polyethylene-co-octene (PE-PO), but this substitution is not expected to increase the decrease in transmittance or reflectance.

[0229] While specific embodiments have been described and explained here, those skilled in the art will understand that various modifications and alternatives that are substantially equivalent to or in place of the above-described examples can be implemented without departing from the scope of this disclosure. This application is intended to encompass any application, modification, or variation of the specific embodiments described herein. Accordingly, the scope of this specification is limited only to the claims and equivalents set forth below.

[0230] Furthermore, all publications and patent documents cited herein are incorporated herein by reference to the same extent as when individual documents are specifically cited. In the event of any inconsistency or conflict between the contents of the cited documents and the contents of this specification, the contents of this specification shall prevail. Various embodiments have been described herein by illustrative examples, but these and other embodiments are included within the scope of the following claims.

Claims

1. A polymer multilayer optical film having a first main surface and a second main surface opposite thereto, comprising one or more alternating first and second polymer optical layers that reflect light incident perpendicularly to the first main surface of a wavelength-selective multilayer, and reflecting at least 50%, 60%, 70%, 80%, 90%, or 95% on average of incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength range of 800 nanometers to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm, and the polymer multilayer optical film having a first main surface and a second main surface opposite thereto, comprising one or more alternating first and second polymer optical layers that reflect light incident perpendicularly to the first main surface of a wavelength-selective multilayer, and reflecting at least 50%, 60%, 70%, 80%, 90%, or 95% of incident light over a wavelength reflection bandwidth of at least 30 nanometers in the wavelength range of 800 nanometers to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm, An inorganic multilayer optical film having a first main surface and a second main surface opposite thereto, wherein the second main surface of the inorganic multilayer optical film is bonded to the first main surface of the polymer multilayer optical film, and the inorganic multilayer optical film comprises one or more alternating first and second inorganic optical layers that reflect and absorb as a whole light incident perpendicular to the first main surface of the wavelength-selective multilayer, and reflects and absorbs at least an average of 50%, 60%, 70%, 80%, 90%, or 95% of incident ultraviolet light over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 190 nm to 400 nm, A wavelength-selective multilayer containing [a specific component].

2. The wavelength-selective multilayer according to claim 1, further comprising a structured film having a first main surface and a second main surface opposite thereto, wherein the first main surface has a plurality of structures protruding therefrom, at least a portion of the plurality of structures each having a surface having an inclination, such that the inclination reflects light incident perpendicularly to the first main surface of the structured film and strikes the first main surface of the structured film or the surface of at least one other structure, and the structured film is positioned a) between the first main surface of the polymer multilayer optical film and the second main surface of the inorganic multilayer optical film, or b) adjacent to the second main surface of the polymer multilayer optical film on the opposite side from the inorganic multilayer optical film.

3. The wavelength-selective multilayer according to claim 1 or 2, wherein at least a portion of the structure includes at least one inclined sidewall having an apex angle of 90 degrees or less and an apex angle of 5 degrees, 15 degrees, 25 degrees, 35 degrees or 45 degrees or more.

4. The wavelength-selective multilayer according to claim 2 or 3, wherein at least a portion of the structure has a triangular cross-sectional shape.

5. The wavelength-selective multilayer according to any one of claims 2 to 4, wherein the structure has the shape of a prism, pyramid, inverted pyramid, diffraction grating, inverted cone, or cone.

6. The wavelength-selective multilayer according to any one of claims 2 to 5, wherein the structured film is flexible.

7. The wavelength-selective multilayer according to any one of claims 2 to 6, wherein the structure refracts light incident on the first main surface of the wavelength-selective multilayer at an angle not perpendicular to it, and causes the light to be emitted from the structured film at an angle closer to perpendicular than the angle of incidence.

8. The wavelength-selective multilayer according to any one of claims 1 to 7, further comprising a barrier layer disposed between the second main surface of the inorganic multilayer optical film and the first main surface of the polymer multilayer optical film.

9. The wavelength-selective multilayer according to claim 8, wherein the structured film is located between the first main surface of the polymer multilayer optical film and the second main surface of the inorganic multilayer optical film, and the barrier layer is located between the first main surface of the structured film and the second main surface of the inorganic multilayer optical film.

10. The wavelength-selective multilayer according to claim 8 or 9, wherein the barrier layer includes an inorganic layer.

11. The wavelength-selective multilayer according to claim 10, wherein the thickness of the inorganic layer is 15 to 60 nanometers.

12. The wavelength-selective multilayer according to any one of claims 8 to 11, wherein the barrier layer further comprises a (co)polymer layer laminated on the inorganic layer.

13. The wavelength-selective multilayer according to claim 12, wherein the barrier layer further comprises a (co)polymer layer disposed between the inorganic layer and the first main surface of the polymer multilayer optical film.

14. The wavelength-selective multilayer according to any one of claims 1 to 13, wherein the polymer multilayer optical film further comprises a third polymer optical layer disposed between the first polymer optical layer and the second polymer optical layer in at least one pair of the alternating first and second polymer optical layers.

15. The wavelength-selective multilayer according to any one of claims 1 to 14, wherein, of the light incident perpendicularly to the first main surface of the wavelength-selective multilayer, it transmits at least 50%, 60%, 70%, 80%, 90%, or 95% on average of the perpendicularly incident light in the wavelength range of over 400 nanometers (nm) up to 700 nm, over 400 nm up to 1100 nm, or over 400 nm up to 1350 nm.

16. The wavelength-selective multilayer according to any one of claims 1 to 15, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide, titanium oxide, silicon oxynitride, molybdenum oxide, tungsten oxide, silicon nitride, indium tin oxide, hafnium oxide, tantalum oxide, zirconium oxynitride, zirconium oxide, aluminum zinc oxide, or zinc oxide, and the second optical layer of the inorganic multilayer optical film comprises at least one of silicon oxide, silicon aluminum oxide, N-type or P-type doped silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, calcium fluoride, indium tin oxide, or zinc oxide.

17. The wavelength-selective multilayer according to any one of claims 1 to 16, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and the second optical layer of the inorganic multilayer optical film comprises silicon aluminum oxide.

18. The wavelength-selective multilayer according to any one of claims 1 to 17, wherein the first optical layer of the inorganic multilayer optical film comprises at least one of niobium oxide or titanium oxide, and the second optical layer of the inorganic multilayer optical film comprises silicon oxide.

19. A wavelength-selective multilayer according to any one of claims 1 to 18, wherein the average transmittance in the wavelength range of 400 nm to 700 nm, 400 nm to 1100 nm, or 400 nm to 1350 nm decreases by less than 20%, less than 10%, less than 5%, or less than 1% after irradiation with a certain amount of ultraviolet light.

20. A wavelength-selective multilayer according to any one of claims 1 to 19, wherein the average reflectance in the wavelength range of 800 nm to 1200 nm, 1200 nm to 1600 nm, or 800 nm to 1600 nm decreases by less than 20%, less than 10%, less than 5%, or less than 1% after irradiation with a certain amount of ultraviolet light.

21. The wavelength-selective multilayer according to any one of claims 1 to 20, wherein the polymer multilayer optical film includes a third harmonic and reflects at least 80%, 90%, or 95% of light incident perpendicularly to the first main surface of the wavelength-selective multilayer over a wavelength bandwidth of at least 30 nanometers in the wavelength range of 340 nm to 400 nm, 350 nm to 400 nm, or 365 nm to 400 nm.

22. A solar cell array comprising the wavelength-selective multilayer according to any one of claims 1 to 21, wherein the wavelength-selective multilayer is disposed on the outer surface of the solar cell array.

23. The solar cell array according to claim 22, further comprising a barrier layer disposed between the solar cell array and the wavelength-selective multilayer.

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