Color radiative cooling optical thin film and method of making

Abstract

This invention discloses a color radiation-cooled optical thin film, comprising a structure of MDM'DM(A1A2)^s stacked sequentially from bottom to top. The structure is asymmetric, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, and MDM'DM serves as a visible and near-infrared band modulation film layer. This invention also discloses a method for preparing the color radiation-cooled optical thin film, which has advantages such as wide color gamut tunability, high saturation, low solar absorption, and high emissivity through an atmospheric transparent window.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to a color radiation-cooled optical thin film and its preparation method. Background Technology

[0002] Radiation cooling, a novel cooling technology, utilizes the high emissivity of the atmospheric transparency window (8-13 μm) through spectral modulation to radiate heat into space. Notably, this cooling process requires no energy consumption. This method can be used to produce clothing for human body thermal regulation, or directly applied to building exteriors, and combined with color principles for automotive paint, among other applications.

[0003] Traditional radiation-cooling films, designed to reflect sunlight and reduce the absorption of solar heat radiation, often exhibit high reflectivity in the visible light spectrum, resulting in a consistently silvery-white appearance. However, in today's society, aesthetic standards are increasingly stringent, and a uniform silvery-white color no longer aligns with modern aesthetic norms. Furthermore, its consistently high reflectivity to visible light contributes to light pollution to some extent.

[0004] Patent CN13791468B discloses a method for manufacturing a color radiation-cooled thin film. This patent uses PET, PEN, etc., as a substrate layer, and employs a metal layer, a spacer layer, and a Bragg reflector layer to form a Tamm structure. High-quality selective absorption of visible light is achieved by exciting Tamm resonance at the interface between the metal layer and the spacer layer. This patent can obtain a radiation-cooled thin film with good color rendering performance; however, structurally, in addition to the aforementioned metal layer, spacer layer, and Bragg reflector layer (where the Bragg reflector layer contains at least three layers), an external functional layer and a protective layer are also required to achieve color radiation cooling, making it relatively complex.

[0005] Patent CN113234367B discloses a method for manufacturing a colored radiation-cooling film. This patent uses polyacrylate / waterborne polyvinylidene fluoride resin, inorganic fillers, and additives to form the radiation-cooling film layer; and employs polystyrene microspheres and polyacrylate / waterborne polyvinylidene fluoride resin to construct the structural color layer. This method requires many types of organic compounds, and the preparation process is relatively complex and environmentally unfriendly.

[0006] Patent CN202010898293.5 discloses a composite colored radiative cooling thin film and its preparation method. This composite thin film uses a polymer substrate, incorporating phase change microcapsules and pigments, and is prepared using electrospinning technology. While this patent achieves the desired color through chemical means by doping with different types of pigments, the addition of pigments leads to increased solar radiation absorption, reducing the efficiency of radiative cooling. Furthermore, the light absorption of the pigment depends on the fundamental absorption characteristics of the doped material, making it difficult to freely and precisely control.

[0007] To address the above issues, it is of great significance to research a colored radiation cooling film that can be widely used in everyday life scenarios. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a color radiation-cooled optical thin film, which has the advantages of wide color gamut tunability, high saturation, low solar absorption, and high emissivity of atmospheric transparent window.

[0009] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows:

[0010] This invention provides a color radiation-cooled optical thin film, which includes a structure stacked sequentially from bottom to top: MDM'DM(A1A2)^s. The structure of this thin film is asymmetric, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (s is a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, achieving high absorption in the 8-13μm wavelength range. MDM'DM serves as a visible and near-infrared band modulation film layer, employing a dual-FP cavity coupled symmetric structure color film layer centered on the coupling layer M'. This achieves high reflectivity in the 400-2500nm solar light band and adjusts the coupling degree of the dual-FP cavities in the 400-800nm ​​visible light range by adjusting the thickness of M', which manifests as adjusting the width of the absorption peak in the spectrum.

[0011] Furthermore, the reflectivity of the first metal layer M and the second metal layer M' is greater than 80% in the wavelength range of 0.4-1.3μm, and the material of the first metal layer M is one or more of Ag, Au, Al and Cu;

[0012] The extinction coefficients of the first absorption layer A1 and the second absorption layer A2 are between 0 and 3 in the wavelength range of 8-13 μm. The material of the first absorption layer A1 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2, and the material of the second absorption layer A2 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2.

[0013] The refractive index of the dielectric layer D is between 1.6 and 3.5, and the material of the dielectric layer D is one of Ta2O5, Al2O3, TiO2, Nb2O5, Y2O3 and LaTiO3.

[0014] Furthermore, the thickness of the first absorption layer A1 and the second absorption layer A2 ranges from 400 to 2500 nm.

[0015] The thickness of the first metal layer M is between 10-30 nm;

[0016] The thickness of the second metal layer M' is between 10-50 nm;

[0017] The thickness of the dielectric layer D ranges from 55 to 150 nm.

[0018] Furthermore, the first absorption layer A1 and the second absorption layer A2 are made of different materials and have different thicknesses.

[0019] Furthermore, when the number of superposition periods s = 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500 nm; when the number of superposition periods s ≥ 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2000 nm.

[0020] This invention also provides a method for preparing a color radiation-cooled optical thin film, which requires the provision of the aforementioned color radiation-cooled optical thin film and includes the following steps:

[0021] Step 1: The thin film to be deposited has an asymmetric structure, with the structure: MDM'DM(A1A2)^s, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods, s is a positive integer, M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer.

[0022] Step 2: Set the total number of layers in the thin film structure, the material used for each layer, the thickness of each layer, and the distribution between the layers according to the user's functional requirements;

[0023] The first layer is the first metal layer M, the second layer is the dielectric layer D, the third layer is the second metal layer M', the fourth layer is the dielectric layer D, and the fifth layer is the first metal layer M;

[0024] If s = 1, then the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2;

[0025] If s≥2, then the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2; repeat the structure of the sixth to seventh layers to set the eighth to the last layer;

[0026] Step 3: Clean the surface of the substrate;

[0027] Step 4: Grow the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating.

[0028] Step 5: Separate the substrate from the first layer to obtain the prepared target film.

[0029] Furthermore, in step 4, when growing the first absorption layer A1, the second absorption layer A2, and the dielectric layer D, electron beam evaporation ion-assisted deposition is used for growth, with the voltage of the ion source set to 350V and the oxygen flow rate of the electron gun set to 0; when growing the first metal layer M and the second metal layer M', resistance heating evaporation ion-assisted deposition is used for growth, with the voltage of the ion source set to 350V and the oxygen flow rate of the electron gun set to 0.

[0030] Furthermore, the substrate material may be polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate, cellulose triacetate, polymethyl methacrylate, polycarbonate / polymethyl methacrylate composite material, polyimide, polypropylene, polyvinyl chloride, polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane elastomer, polytetrafluoroethylene, fluoroethyl propylene, or polydifluoroethylene.

[0031] The substrate has a release layer material on its upper surface, which separates the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

[0032] This invention also provides a color radiation-cooled optical thin film, which includes a structure stacked sequentially from bottom to top: (A2A1)^sMDM'DM(A1A2)^s. The structure of the thin film is a symmetrical structure centered on M', where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (s is a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, achieving high absorption in the 8-13μm wavelength range. MDM'DM serves as a visible and near-infrared band modulation film layer, employing a dual-FP cavity coupled symmetrical structure color film layer centered on the coupling layer M'. This achieves high reflectivity in the 400-2500nm solar light band and adjusts the coupling degree of the dual-FP cavities by adjusting the thickness of M' in the 400-800nm ​​visible light range, which is reflected in the spectrum by adjusting the width of the absorption peak.

[0033] This invention also provides a method for preparing a color radiation-cooled optical thin film, which requires the provision of the aforementioned color radiation-cooled optical thin film and includes the following steps:

[0034] Step 1: The thin film to be deposited has a symmetrical structure, with the structure: (A2A1)^sMDM'DM(A1A2)^s. The structure of this thin film is a symmetrical structure centered on M', where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods, s is a positive integer, M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer.

[0035] Step 2: Set the total number of layers in the thin film structure, the material used for each layer, the thickness of each layer, and the distribution between the layers according to the user's functional requirements;

[0036] The i-th layer at the very center is the second metal layer M', the (i-1)-th layer is the dielectric layer D, the (i+1)-th layer is the dielectric layer D, the (i-2)-th layer is the first metal layer M, and the (i+2)-th layer is the first metal layer M.

[0037] If s = 1, then i = 5; the first layer is the second absorption layer A2, the second layer is the first absorption layer A1; the eighth layer is the first absorption layer A1, and the ninth layer is the second absorption layer A2;

[0038] If s≥2, then the first layer is the second absorption layer A2, and the second layer is the first absorption layer A1; repeat the structure from the first layer to the second layer to set the third layer to the (i-3)th layer; the (i+3)th layer to the last layer is symmetrical to the (i-3)th layer to the first layer;

[0039] Step 3: Clean the surface of the substrate;

[0040] Step 4: Grow the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating.

[0041] Step 5: Separate the substrate from the first layer to obtain the prepared target film.

[0042] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0043] 1. Using a symmetrical or asymmetrical structure of complementary MDM'DM dual FP cavity as the control film layer for visible and near-infrared bands, while reflecting sunlight as much as possible, an absorption band with adjustable width and depth is formed, thereby obtaining a wider tunable color gamut and higher saturation.

[0044] 2. By adopting the M(A1A2)^s structure, a high absorption rate of 8-13μm can be achieved with fewer film layers (preferably 3 layers), resulting in better radiation performance.

[0045] 3. The structure is simple and can be easily extended into a symmetrical colored radiation cooling film. Moreover, the materials are all inorganic and do not require degradation, making it environmentally friendly. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the atmospheric window radiation film layer structure provided by the present invention.

[0048] Figure 2 This is a schematic diagram of the MDM'DM structure for dual FP cavity coupling provided by the present invention.

[0049] Figure 3 The diagram shows the atmospheric window radiation film and the visible and near-infrared band modulation film provided by the present invention, which are coupled to form a colored radiation cooling thin film structure.

[0050] Figure 4 This is a schematic diagram of the symmetrical color radiation cooling thin film structure provided by the present invention.

[0051] Figure 5 This is a schematic diagram of the reflectivity in the visible light band for Embodiment 1 of the present invention.

[0052] Figure 6 A schematic diagram of reflectivity for other solar wavelengths (800-2500nm) in Embodiment 1 of the present invention.

[0053] Figure 7 This is a schematic diagram of the absorption rate of the atmospheric transparency window band (8-13μm) provided in Embodiment 1 of the present invention.

[0054] Figure 8 This is a schematic diagram of chromaticity coordinates for Embodiment 1 of the present invention.

[0055] Figure 9 This is a schematic diagram of the reflectivity in the visible light band of Embodiment 2 provided by the present invention.

[0056] Figure 10 A schematic diagram of reflectivity for other solar wavelengths (800-2500nm) in Embodiment 2 of the present invention.

[0057] Figure 11 This is a schematic diagram of the absorption rate of the atmospheric transparency window band (8-13μm) in Embodiment 2 of the present invention.

[0058] Figure 12 This is a schematic diagram of chromaticity coordinates for Embodiment 2 of the present invention.

[0059] Figure 13 This is a schematic diagram of the reflectivity in the visible light band for Embodiment 3 of the present invention.

[0060] Figure 14 A schematic diagram of reflectance for other solar wavelengths (800-2500nm) in Embodiment 3 of the present invention.

[0061] Figure 15 This is a schematic diagram of the absorption rate of the atmospheric transparency window band (8-13μm) in Embodiment 3 of the present invention.

[0062] Figure 16 A schematic diagram of the coordinates of three colors provided in the embodiment of the present invention.

[0063] Figure 17 This is a schematic diagram of the reflectivity in the visible light band for Embodiment 4 of the present invention.

[0064] Figure 18 A schematic diagram of reflectivity for other solar wavelengths (800-2500nm) in Embodiment 4 of the present invention.

[0065] Figure 19 This is a schematic diagram of the absorption rate of the atmospheric transparency window band (8-13μm) in Embodiment 4 of the present invention.

[0066] Figure 20 A schematic diagram of four-color coordinates provided by the present invention.

[0067] Figure 21 This is a schematic diagram of the reflectivity in the visible light band for Embodiment 4 of the present invention.

[0068] Figure 22 A schematic diagram of reflectivity for other solar wavelengths (800-2500nm) in Embodiment 4 of the present invention.

[0069] Figure 23 This is a schematic diagram of the absorption rate of the atmospheric transparency window band (8-13μm) in Embodiment 4 of the present invention.

[0070] Figure 24 A schematic diagram of four-color coordinates provided by the present invention.

[0071] Figure 25 A schematic diagram of the technical solution provided by the present invention.

[0072] Figure 26 This is a schematic diagram of the process flow provided by the present invention. Detailed Implementation

[0073] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] The design concept of this invention is as follows:

[0075] To achieve high emissivity of the atmospheric window and modulation of visible light, this invention describes the film layer in two parts: an atmospheric window radiation film layer and a visible light and near-infrared band modulation film layer.

[0076] 1. Atmospheric window radiation film layer

[0077] For the design of the atmospheric window radiation film layer, considering the need for high absorptivity (emissivity) in the atmospheric transparent window (8-13 μm) while minimizing the impact on the visible light band, it is necessary to select a material that is transparent to visible light and has a high extinction coefficient in the 8-13 μm range. Based on the above spectral requirements, this invention provides a structure of M(A1A2)^s (where M represents the first metal layer, A1 represents the first absorption layer, A2 represents the second absorption layer, and s represents the number of stacking periods) to achieve high absorptivity in the 8-13 μm range, such as... Figure 1As shown (most preferably MA1A2, i.e., s=1), this invention mainly utilizes the intrinsic absorption and destructive interference effect of the material for absorption, resulting in a structure with high absorptivity in the 8-13 μm range. The first metal layer M has a thickness of 10-30 nm and participates in forming the reflector of the resonant cavity, simultaneously balancing reflectivity and color saturation. When s is 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500 nm; when s>1, the thickness of the first absorption layer A1 and the second absorption layer A2 is reduced as needed to meet the requirement of high absorptivity. The first metal layer M has a reflectivity greater than 80% in the 0.4-1.3 μm range. The material of the metal layer includes one or more of Ag, Au, Al, and Cu, with Ag being the most preferred. Within the 8-13 μm range, the extinction coefficients of the first absorption layer A1 and the second absorption layer A2 range from 0-3, and the first absorption layer A1 and the second absorption layer A2 are made of different materials. The thicknesses of the first absorption layer A1 and the second absorption layer A2 are different. Depending on the period s, the first absorption layer A1 and the second absorption layer A2 can be two different materials: TiO2, SiO2, Al2O3, Si3N4, and HfO2. Considering the simplicity of the structure, when s = 1, TiO2 is preferred as the first absorption layer A1 and SiO2 is preferred as the second absorption layer A2.

[0078] 2. Visible and near-infrared band modulation film layer

[0079] For the design of tunable films in the visible and near-infrared bands, the reflectivity in the solar radiation band (0.4-2.5μm) should be maximized to minimize heat absorption. Therefore, the introduction of highly reflective metallic materials is the first consideration. However, high reflectivity in the solar radiation band would result in the radiative cooling film always appearing silvery-white. A single silvery-white color does not conform to modern aesthetic standards and may cause light pollution during widespread application. Against this backdrop, we construct a photocell (FP) cavity on a single metallic reflective layer and design a complementary color structure. This allows for selective absorption in the visible light band while minimizing the impact on its high reflectivity characteristics across the entire solar radiation band. Considering structural symmetry and color saturation, a symmetrical color film structure, the MDM'DM structure, is designed with a dual FP cavity coupling centered on the coupling layer M'. Compared to a single FP cavity, the MDM'DM structure can achieve a wider tunable color gamut and better color saturation, such as... Figure 2As shown, this structure exhibits high reflectivity in the 400-2500nm solar wavelength range, while also allowing for adjustment of the coupling degree between the two resonant cavities in the 400-800nm ​​visible light range. This is achieved by altering the thickness of the second metal layer M' (thickness control range: 15-50nm, within which significant mode splitting occurs, favoring the formation of a wider absorption band. When the thickness is below 15nm, mode splitting is significant, the two resonant peaks are completely separated, forming two absorption bands, which is detrimental to the formation of high-saturation colors. When the thickness is greater than 50nm, the coupling strength weakens, the modes gradually decouple, and the two resonant peaks merge into one, forming a narrow absorption valley, which is also unfavorable for the formation of high-saturation colors). Spectrally, this manifests as an adjustable absorption peak width. Furthermore, by simultaneously changing the thickness of the dielectric layer D (thickness control range: 55-113nm, within which the absorption band can be controlled to be within the visible light range, forming complementary colors. If the thickness is outside this range, the absorption valley is not within the visible light range, and no color can be produced), the generated color can be controlled.

[0080] The coupling principle of dual resonant cavities is analyzed below. For a single resonant cavity, its resonance condition satisfies:

[0081] 2nL=mλ

[0082] Where n represents the refractive index of the cavity medium, L represents the optical thickness of the cavity, and m represents the order (integer) of the resonant mode. λ represents the resonant wavelength. For two independent resonant cavities, assume their natural resonant frequencies are respectively:

[0083]

[0084] Where c is the speed of light in a vacuum, approximately 3*10⁻⁶. 8 At this speed (m / s), the two resonant cavities are independent, and light does not propagate between them. When the two resonant cavities are coupled (in this invention, a shared metal layer is used for coupling), light can propagate and interact between the two resonant cavities. This coupling changes the resonance conditions of the system, causing the original single resonant mode to split into two new modes. The resonant frequency f of the coupled system is... ± It can be represented as:

[0085]

[0086] Among them, f ± Let represent the frequencies of the symmetric and antisymmetric modes after mode splitting, respectively, and k represent the coupling strength between the two resonators. The coupling strength k is a key parameter for mode splitting. It depends on the properties and thickness of the coupling layer:

[0087] T = e -2αd

[0088] Where T is the transmittance of the metal coupling layer (the attenuation of light in the metal layer follows Beer-Lambert's law), and α is the absorption coefficient (for this invention, a metal is used as the coupling layer). Where μ is the extinction coefficient of the material used in the coupling layer). After mode splitting occurs when two resonant cavities with the same intrinsic frequency are coupled through a shared metal layer, two discrete resonant peaks can be generated in the spectrum, with frequency and wavelength intervals respectively:

[0089] Δf=2k,

[0090] The following explanation uses this invention as an example. According to the above theory, by controlling the thickness of the intermediate metal coupling layer, the coupling strength k is adjusted to a smaller value, resulting in a smaller wavelength interval between the two resonant peaks generated by mode splitting, thus obtaining a larger absorption band. The position of the resonant peaks can be adjusted by simultaneously controlling the optical thickness of the two resonant cavities.

[0091] This allows for the production of a structural color film with a wide color gamut and high saturation, while reflecting most sunlight. The first metal layer M and the second metal layer M' have a reflectivity greater than 80% in the 0.4-1.3 μm range. The materials of the first metal layer M and the second metal layer M' include one or more of Ag, Au, Al, and Cu, with Ag being the most preferred considering reflectivity. The refractive index of the dielectric layer D is between 1.6 and 3.5, and the material can be one of Ta₂O₅, Al₂O₃, TiO₂, Nb₂O₅, Y₂O₃, and LaTiO₃, with LaTiO₃ being preferred due to its high refractive index.

[0092] 3. Combination of atmospheric window radiation film layer with visible and near-infrared band modulation film layer

[0093] The aforementioned atmospheric window radiation film layer and the visible and near-infrared band modulation film layer are coupled through a metal layer M to form a color radiative cooling film, such as... Figure 3 As shown. This structure can achieve high emissivity (greater than 85%) in the atmospheric window, high average reflectivity in the solar light band (greater than 90%), and high color saturation. In summary, the optimal choices are: TiO2 as Al, SiO2 as Al2, Ag as M and M', and LaTiO3 as D. It can also be observed that because the color structure MDM'DM has symmetry from the initial design, the above-mentioned radiation-cooling thin film can be easily extended into a symmetrical thin film without causing excessive structural complexity. The extended structure is as follows: Figure 4As shown. For symmetrical thin-film structures, the incident light from the front and back sides of the film system has the same spectral characteristics. Therefore, it can be processed into a micro-element radiation-cooling thin film, which can then be prepared into a coating material and applied to the surfaces of vehicles, buildings, etc., by spraying, scraping, brushing, etc. This method can be widely used on irregular object surfaces, without being limited by the size or shape of the coating process. For easier intuitive understanding, a simplified technical solution flowchart is shown below. Figure 25 As shown.

[0094] Compared with existing technologies, the color radiation cooling film provided by this invention consists of an atmospheric window radiation film layer and visible and near-infrared band modulation film layers. It achieves precise spectral control within a simple structure, exhibiting better color controllability, and can be easily extended into a symmetrical color radiation cooling film. Furthermore, all raw materials used are inorganic, requiring no degradation and being environmentally friendly.

[0095] Option 1:

[0096] A colored radiation-cooled optical thin film includes a structure stacked sequentially from bottom to top: MDM'DM(A1A2)^s. The structure of the thin film is asymmetric, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (s is a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, achieving high absorption in the 8-13 μm wavelength range. MDM'DM serves as a visible and near-infrared band modulation film layer, employing a dual-FP cavity coupled symmetric structure color film layer centered on the coupling layer M'. This achieves high reflectivity in the 400-2500 nm solar light band and adjusts the coupling degree of the dual-FP cavities by adjusting the thickness of M' in the 400-800 nm visible light range, which is manifested in the spectrum as adjusting the width of the absorption peak.

[0097] Preferably, the reflectivity of the first metal layer M and the second metal layer M' is greater than 80% in the wavelength range of 0.4-1.3μm, and the material of the first metal layer M is one or more of Ag, Au, Al and Cu;

[0098] The extinction coefficients of the first absorption layer A1 and the second absorption layer A2 are between 0 and 3 in the wavelength range of 8-13 μm. The material of the first absorption layer A1 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2, and the material of the second absorption layer A2 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2.

[0099] The refractive index of the dielectric layer D is between 1.6 and 3.5, and the material of the dielectric layer D is one of Ta2O5, Al2O3, TiO2, Nb2O5, Y2O3 and LaTiO3.

[0100] Preferably, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500 nm.

[0101] The thickness of the first metal layer M is between 10-30 nm;

[0102] The thickness of the second metal layer M' is between 10-50 nm;

[0103] The thickness of the dielectric layer D ranges from 55 to 150 nm.

[0104] Preferably, the first absorption layer A1 and the second absorption layer A2 are made of different materials and have different thicknesses.

[0105] Preferably, the number of stacking periods s = 1. When the number of stacking periods s = 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500 nm; when the number of stacking periods s ≥ 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2000 nm.

[0106] Option 2:

[0107] This invention also provides a method for preparing a color radiation-cooled optical thin film, which requires the provision of the aforementioned color radiation-cooled optical thin film and includes the following steps:

[0108] Step 1: The thin film to be deposited has an asymmetric structure, with the structure: MDM'DM(A1A2)^s, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods, s is a positive integer, M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer.

[0109] Step 2: Set the total number of layers in the thin film structure, the material used for each layer, the thickness of each layer, and the distribution between the layers according to the user's functional requirements;

[0110] The first layer is the first metal layer M, the second layer is the dielectric layer D, the third layer is the second metal layer M', the fourth layer is the dielectric layer D, and the fifth layer is the first metal layer M;

[0111] If s = 1, then the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2;

[0112] If s≥2, then the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2; repeat the structure of the sixth to seventh layers to set the eighth to the last layer;

[0113] Step 3: Clean the surface of the substrate;

[0114] Step 4: Grow the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating.

[0115] Step 5: Separate the substrate from the first layer to obtain the prepared target film.

[0116] Preferably, in step 4, when growing the first absorption layer A1, the second absorption layer A2, and the dielectric layer D, electron beam evaporation ion-assisted deposition is used, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0; when growing the first metal layer M and the second metal layer M', resistance heating evaporation ion-assisted deposition is used, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0.

[0117] The substrate material can be polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate (PET), cellulose triacetate (TAC), polymethyl methacrylate (PMMA), polycarbonate / polymethyl methacrylate composite (PC / PMMA), polyimide (PI), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), polyurethane elastomer (TPU), polytetrafluoroethylene (PTFE), fluoroethyl propylene (FEP), or polydifluoroethylene (PVDF).

[0118] The substrate has a release layer material on its upper surface, which separates the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

[0119] Option 3:

[0120] This invention also provides a color radiation-cooled optical thin film, which includes a structure stacked sequentially from bottom to top: (A2A1)^sMDM'DM(A1A2)^s. The structure of the thin film is a symmetrical structure centered on M', where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (s is a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, achieving high absorption in the 8-13μm wavelength range. MDM'DM serves as a visible and near-infrared band modulation film layer, employing a dual-FP cavity coupled symmetrical structure color film layer centered on the coupling layer M'. This achieves high reflectivity in the 400-2500nm solar light band and adjusts the coupling degree of the dual-FP cavities by adjusting the thickness of M' in the 400-800nm ​​visible light range, which is reflected in the spectrum by adjusting the width of the absorption peak.

[0121] Preferably, the reflectivity of the first metal layer M and the second metal layer M' is greater than 80% in the wavelength range of 0.4-1.3μm, and the material of the first metal layer M is one or more of Ag, Au, Al and Cu;

[0122] The extinction coefficients of the first absorption layer A1 and the second absorption layer A2 are between 0 and 3 in the wavelength range of 8-13 μm. The material of the first absorption layer A1 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2, and the material of the second absorption layer A2 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2.

[0123] The refractive index of the dielectric layer D is between 1.6 and 3.5, and the material of the dielectric layer D is one of Ta2O5, Al2O3, TiO2, Nb2O5, Y2O3 and LaTiO3.

[0124] Preferably, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500 nm.

[0125] The thickness of the first metal layer M is between 10-30 nm;

[0126] The thickness of the second metal layer M' is between 10-50 nm;

[0127] The thickness of the dielectric layer D ranges from 55 to 150 nm.

[0128] Preferably, the first absorption layer A1 and the second absorption layer A2 are made of different materials and have different thicknesses.

[0129] Preferably, the number of stacking periods s = 1. When the number of stacking periods s = 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500 nm; when the number of stacking periods s ≥ 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2000 nm.

[0130] Option 4:

[0131] This invention also provides a method for preparing a color radiation-cooled optical thin film, which requires the provision of the aforementioned color radiation-cooled optical thin film and includes the following steps:

[0132] Step 1: The thin film to be deposited has a symmetrical structure, with the structure: (A2A1)^sMDM'DM(A1A2)^s. The structure of this thin film is a symmetrical structure centered on M', where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods, s is a positive integer, M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer.

[0133] Step 2: Set the total number of layers in the thin film structure, the material used for each layer, the thickness of each layer, and the distribution between the layers according to the user's functional requirements;

[0134] The i-th layer at the very center is the second metal layer M', the (i-1)-th layer is the dielectric layer D, the (i+1)-th layer is the dielectric layer D, the (i-2)-th layer is the first metal layer M, and the (i+2)-th layer is the first metal layer M.

[0135] If s = 1, then i = 5; the first layer is the second absorption layer A2, the second layer is the first absorption layer A1; the eighth layer is the first absorption layer A1, and the ninth layer is the second absorption layer A2;

[0136] If s≥2, then the first layer is the second absorption layer A2, and the second layer is the first absorption layer A1; repeat the structure from the first layer to the second layer to set the third layer to the (i-3)th layer; the (i+3)th layer to the last layer is symmetrical to the (i-3)th layer to the first layer;

[0137] Step 3: Clean the surface of the substrate;

[0138] Step 4: Grow the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating.

[0139] Step 5: Separate the substrate from the first layer to obtain the prepared target film.

[0140] Preferably, in step 4, when growing the first absorption layer A1, the second absorption layer A2, and the dielectric layer D, electron beam evaporation ion-assisted deposition is used, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0; when growing the first metal layer M and the second metal layer M', resistance heating evaporation ion-assisted deposition is used, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0.

[0141] Preferably, the substrate material is polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate (PET), cellulose triacetate (TAC), polymethyl methacrylate (PMMA), polycarbonate / polymethyl methacrylate composite (PC / PMMA), polyimide (PI), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), polyurethane elastomer (TPU), polytetrafluoroethylene (PTFE), fluoroethyl propylene (FEP), or polyvinyl difluoroethylene (PVDF).

[0142] The substrate has a release layer material on its upper surface, which separates the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

[0143] In this specific embodiment, the thin film can be prepared using physical vapor deposition (PVD) methods, including combinations of different techniques such as ion beam sputtering deposition (IBS), magnetron sputtering deposition (MS), electron beam evaporation (EB), or electron beam evaporation ion-assisted deposition (EBD-IAD). Alternatively, chemical vapor deposition (CVD) or liquid-phase coating methods for pearlescent thin films can also be used to prepare the thin film.

[0144] For ease of explanation and consideration of the actual multilayer film preparation process, the electron beam evaporation ion-assisted deposition (EBD-IAD) technique is used for process preparation. The basic principle of this technique is as follows:

[0145] 1. An electron gun generates a high-energy electron beam with adjustable power. The electron beam is guided and accelerated to the target material by electric and magnetic fields. An electron gun generally includes a thermionic cathode (usually a heated tungsten filament) that emits electrons and an anode that accelerates electrons.

[0146] 2. A high-energy electron beam bombards the target material, converting its energy into heat energy, which heats the target material to its evaporation temperature.

[0147] 3. Evaporated material atoms or molecules fly through a vacuum to the substrate surface, where they condense to form a thin film. The ion beam adds energy to the outermost atomic layer during film formation, influencing the hardness, density, and surface morphology of the microstructure for better bonding and adhesion. The use of an ion source can effectively improve film quality, including density, hardness, and adhesion, while providing better control over surface texture and microstructure. Although the ion beam only barely penetrates the top atoms of the growing film, the ions released by the ion beam result in a denser film due to the more compact arrangement of the forming microcrystals. Furthermore, this process takes place in a vacuum, so the evaporated atoms or molecules interact minimally with other gas molecules during their flight, contributing to the formation of high-quality films.

[0148] However, in the actual preparation process, the influence of many other conditions needs to be considered:

[0149] 1. Stable operating conditions must be ensured for the vacuum coating machine. This includes ensuring the working status of the electron gun and ion source, the working status of each mechanical pump, the cleanliness of the vacuum chamber, and the working status of the film thickness controller.

[0150] 2. Preparations before coating. This includes inputting the film system, placing the coating material, and selecting and wiping the coating substrate.

[0151] 3. Vacuuming and material pre-melting (if necessary).

[0152] 4. Evaporation to prepare the target thin film.

[0153] by Figure 3 The structures shown are preferably TiO2 as Al, SiO2 as A2, Ag as M and M', and LaTiO3 as D, as examples for illustration.

[0154] S1. The substrate is cleaned using a mixture of ethanol and acetone in a 1:3 ratio. Before growth begins, the substrate surface is bombarded with an ion source to remove unwanted surface impurities.

[0155] S2. On the above substrate, the first Ag layer is grown by resistance heating evaporation ion-assisted deposition. The ion source voltage is set to 350V and the electron gun oxygen flow rate is set to 0 to prevent Ag oxidation.

[0156] S3. On the first layer mentioned above, a second layer of LaTiO3 is grown using electron beam evaporation (using a high-energy electron beam to bombard the evaporation material, causing it to be locally heated and vaporized into steam. Electron beams can generate very high temperatures (>3000℃), suitable for high-melting-point materials such as SiO2 and TiO2. The evaporation rate and deposition thickness can be precisely controlled by the electron beam energy) ion-assisted deposition method. The ion source voltage is set to 350V, and the electron gun oxygen flow rate is set to 0.

[0157] S4. On the second layer mentioned above, a third Ag layer is grown using resistance heating evaporation (the material is heated to vaporization by passing current through a high-resistance heating wire, such as a tungsten boat or molybdenum boat. This method is suitable for low-melting-point materials, such as Ag, Al, and Au, as it does not require excessively high temperatures and avoids material loss or oxidation caused by overheating) and ion-assisted deposition. The ion source voltage is set to 350V, and the electron gun oxygen flow rate is set to 0 to prevent Ag oxidation.

[0158] S5. On the above-mentioned third layer, a fourth layer of LaTiO3 is grown by electron beam evaporation ion-assisted deposition, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0.

[0159] S6. On the above-mentioned fourth layer, the fifth Ag layer is grown by resistance heating evaporation ion-assisted deposition. The ion source voltage is set to 350V and the electron gun oxygen flow rate is set to 0 to prevent Ag oxidation.

[0160] S7. On the aforementioned 5th layer, a 6th TiO2 layer is grown using electron beam evaporation ion-assisted deposition (pre-melting is required). The ion source voltage is set to 350V, and the electron gun oxygen flow rate is controlled (the raw material for preparing TiO2 is Ti3O5, which is closer to the chemical formula of the target film than metallic titanium or other titanium oxides such as TiO, reducing the need for additional oxidation. Evaporation of TiO2 requires extremely high temperatures, which can only be met by high-power electron beam evaporation equipment or laser evaporation equipment. Furthermore, at high temperatures, uneven evaporation and melting may occur on the material surface during TiO2 evaporation, leading to splashing on the evaporation source surface and affecting the uniformity and optical quality of the film). This ensures a vacuum level of 2.2-2.3 × 10⁻⁶. -3 Between Pa.

[0161] S7. On the above-mentioned 6th layer, the 7th layer of SiO2 is grown by electron beam evaporation ion-assisted deposition (pre-melting is required). The ion source voltage is set to 350V and the electron gun oxygen flow rate is set to 0.

[0162] For a more intuitive and convenient explanation, a simplified process flow diagram is shown below. Figure 26 As shown.

[0163] To make the objectives, technical solutions, and advantages of this invention clearer, the following will provide accompanying drawings and embodiments of both asymmetric and symmetric radiation-cooling thin films, and further describe and demonstrate this invention in detail.

[0164] Example 1

[0165] The basic structure of a color radiation cooling thin film is as follows: Figure 3As shown, this colored radiation-cooled thin film has only seven simple layers, where A1 is preferably TiO2, A2 is preferably SiO2, M and M' are preferably Ag, and D is preferably LaTiO3. Its thickness is shown in Table 1.

[0166] Table 1:

[0167] Material Name Thickness (nm) <![CDATA[SiO2]]> 857 <![CDATA[TiO2]]> 1232 Ag 25 <![CDATA[LaTiO3]]> 108.6 Ag 45.25 <![CDATA[LaTiO3]]> 108.6 Ag 25

[0168] This embodiment, by adjusting the thickness of layers M and M', achieves an average reflectivity of 92.6% in the solar radiation band (400-2500nm), reflecting the vast majority of solar radiation and thus reducing heat absorption. Specifically, in the visible light band (400-800nm)... Figure 5 As shown, the remaining solar wavelengths (800-2500nm) are as follows: Figure 6 As shown. This embodiment, by adjusting the thickness of layers A1 and A2, achieves an average absorptivity (emissivity) of 88.25% within the atmospheric transparency window band (8-13 μm), as... Figure 7 As shown, it exhibits excellent radiation capability. The bandwidth of the absorption peak is controlled by adjusting the thickness of the M' layer, while the position of the absorption peak is changed by adjusting the thickness of the D layer, controlling the absorption band to be located in the red band. Other bands maintain high reflectivity. The resulting blue and green bands are superimposed to form a cyan radiation-cooling film. The high reflectivity across the wide visible light spectrum not only achieves color superposition but also reflects most of the solar radiation. The chromaticity coordinates of this embodiment are (0.2384, 0.3249), as shown... Figure 8 As shown.

[0169] Example 2

[0170] The basic structure of a color radiation cooling thin film is as follows: Figure 3 As shown, this colored radiation-cooled thin film has only seven simple layers, where A1 is preferably TiO2, A2 is preferably SiO2, M and M' are preferably Ag, and D is preferably LaTiO3. Its thickness is shown in Table 2.

[0171] Material Name Thickness (nm) <![CDATA[SiO2]]> 857 <![CDATA[TiO2]]> 1232 Ag 22.3 <![CDATA[LaTiO33]]> 86.4 Ag 37.5 <![CDATA[LaTiO3]]> 86.4 Ag 22.3

[0172] This embodiment, by adjusting the thickness of layers M and M', achieves an average reflectivity of 91% within the solar radiation band (400-2500nm), reflecting the vast majority of solar radiation and thus reducing heat absorption. The visible light band, for example... Figure 9 As shown, the remaining solar wavelengths (800-2500nm) are as follows: Figure 10 As shown. This embodiment, by adjusting the thickness of layers A1 and A2, achieves an average absorptivity (emissivity) of 88.25% within the atmospheric transparency window band (8-13 μm), as... Figure 11As shown, it exhibits excellent radiation capability. The bandwidth of the absorption peak is controlled by adjusting the thickness of the M' layer, and the position of the absorption peak is changed by adjusting the thickness of the D layer, controlling the absorption band to be located in the green band. Other bands maintain high reflectivity. The resulting blue and red bands are superimposed to form a magenta radiation-cooling film. The high reflectivity across the wide visible light spectrum not only achieves color superposition but also reflects most of the solar radiation. In this embodiment, the chromaticity coordinates are (0.3743, 0.2398), as shown... Figure 12 As shown.

[0173] Example 3

[0174] The basic structure of a color radiation cooling thin film is as follows: Figure 3 As shown, this colored radiation-cooled thin film has only 7 simple layers, where Al is preferably TiO2, A2 is preferably SiO2, M and M' are preferably Ag, and D is preferably LaTiO3. Its thickness is shown in Table 3.

[0175] Material Name Thickness (nm) <![CDATA[SiO2]]> 857 <![CDATA[TiO2]]> 1232 Ag 27.2 <![CDATA[LaTiO3]]> 61.3 Ag 47 <![CDATA[LaTiO3]]> 61.3 Ag 27.2

[0176] This embodiment, by adjusting the thickness of layers M and M', achieves an average reflectivity of 93% within the solar radiation band (400-2500nm), reflecting the vast majority of solar radiation and thus reducing heat absorption. The visible light band includes... Figure 13 As shown, the remaining solar wavelengths (800-2500nm) are as follows: Figure 14 As shown. This embodiment, by adjusting the thickness of layers A1 and A2, achieves an average absorptivity (emissivity) of 88.23% within the atmospheric transparency window band (8-13 μm). Figure 15 As shown, it exhibits good radiation capability. The bandwidth of the absorption peak is controlled by adjusting the thickness of the M' layer, and the position of the absorption peak is changed by adjusting the thickness of the D layer, resulting in an absorption band located in the blue band. Other bands maintain high reflectivity. The superposition of the reflected green and red bands yields a yellow radiation-cooling film. The high reflectivity across the broad visible light spectrum not only achieves color superposition but also reflects most of the solar radiation. In this embodiment, the chromaticity coordinates are (0.4115, 0.4724), and the radiation-cooling film is yellow. Figure 16 As shown.

[0177] Example 4

[0178] The basic structure of a symmetrical color radiation cooling thin film is as follows: Figure 4 As shown, by simply extending two radiation layers, the asymmetric color radiation cooling thin film is derived into a symmetric one. This symmetric color radiation cooling thin film has only a simple total of 9 layers, where Al is TiO2, A2 is SiO2, M and M' are Al, and D is Ta2O5. Its thickness is shown in Table 4.

[0179]

[0180]

[0181] This embodiment, by adjusting the thickness of layers M and M', achieves an average reflectivity of 75% within the solar radiation band (400-2500nm), reflecting the vast majority of solar radiation and thus reducing heat absorption. The visible light band, for example... Figure 17 As shown, the remaining solar wavelengths (800-2500nm) are as follows: Figure 18 As shown. This embodiment, by adjusting the thickness of layers A1 and A2, achieves an average absorptivity (emissivity) of 88.467% within the atmospheric transparency window band (8-13 μm), as... Figure 19 As shown, it exhibits good radiation capability. The bandwidth of the absorption peak is controlled by adjusting the thickness of the M' layer, and the position of the absorption peak, i.e., the color, is changed by adjusting the thickness of the D layer. Compared to magenta, this embodiment reflects more blue, making it appear purple. The chromaticity coordinates of this embodiment are (0.2954, 0.2223), and the radiation-cooling film is purple, as shown... Figure 20 As shown.

[0182] Example 5

[0183] The basic structure of a symmetrical color radiation cooling thin film is as follows: Figure 4 As shown, by simply extending two radiation layers, the asymmetric color radiation cooling thin film is derived into a symmetric one. This symmetric color radiation cooling thin film has only a simple total of 9 layers, where A1 is selected as Al₂O₃, A2 as SiO₂, M and M' as Al, and D as Al₂O₃. Its thickness is shown in Table 1.

[0184] Material Name Thickness (nm) <![CDATA[SiO2]]> 876 <![CDATA[Al2O3]]> 1394 Al 23.7 <![CDATA[Al2O3]]> 128.57 Al 14.8 <![CDATA[Al2O3]]> 128.57 Al 23.7 <![CDATA[Al2O3]]> 1394 <![CDATA[SiO2]]> 876

[0185] This embodiment, by adjusting the thickness of layers M and M', achieves an average reflectivity of 90.36% in the solar radiation band (400-2500nm), reflecting the vast majority of solar radiation and thus reducing heat absorption. The visible light band, for example... Figure 21 As shown, the remaining solar wavelengths (800-2500nm) are as follows: Figure 22 As shown. This embodiment, by adjusting the thickness of layers A1 and A2, achieves an average absorptivity (emissivity) of 81.381% within the atmospheric transparency window band (8-13 μm), as... Figure 23As shown, it exhibits excellent radiation capability. The bandwidth of the absorption peak is controlled by adjusting the thickness of the M' layer, and the position of the absorption peak is changed by adjusting the thickness of the D layer, placing it in the green and yellow bands. Sky blue is obtained by superimposing reflected blue light with some green light. The high reflectivity across the wide visible light spectrum not only achieves color superposition but also reflects most of the solar radiation. In this embodiment, the chromaticity coordinates are (0.2098, 0.2367), and the radiation-cooling film is sky blue. Figure 24 As shown.

[0186] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A color radiation-cooled optical thin film, characterized in that, The thin film comprises a structure stacked sequentially from bottom to top: MDM'DM(A1A2)^s. This thin film has an asymmetric structure, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (s is a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, achieving high absorption in the 8-13 μm wavelength range through intrinsic absorption and destructive interference effects. MDM'DM serves as a visible and near-infrared band modulation film layer, using a coupling layer M' as... The central dual-FP cavity coupled symmetrical structure color film layer achieves high reflectivity in the 400-2500nm solar light band and adjusts the coupling degree of the dual-FP cavities by adjusting the thickness of M' in the 400-800nm ​​visible light range, which is manifested in the spectrum as adjusting the width of the absorption peak; the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; the thickness range of the first metal layer M is between 10-30nm; the thickness range of the second metal layer M' is between 10-50nm; and the thickness range of the dielectric layer D is between 55-150nm.

2. The colored radiation-cooled optical thin film as described in claim 1, characterized in that, The first metal layer M and the second metal layer M' have a reflectivity greater than 80% in the wavelength range of 0.4-1.3μm, and the material of the first metal layer M is one or more of Ag, Au, Al and Cu; The extinction coefficients of the first absorption layer A1 and the second absorption layer A2 are between 0 and 3 in the wavelength range of 8-13 μm. The material of the first absorption layer A1 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2, and the material of the second absorption layer A2 is one of TiO2, SiO2, Al2O3, Si3N4 and HfO2. The refractive index of the dielectric layer D is between 1.6 and 3.5, and the material of the dielectric layer D is one of Ta2O5, Al2O3, TiO2, Nb2O5, Y2O3 and LaTiO3.

3. The colored radiation-cooled optical thin film as described in claim 1, characterized in that, The first absorption layer A1 and the second absorption layer A2 are made of different materials and have different thicknesses.

4. A method for preparing a colored radiation-cooled optical thin film, characterized in that, The method requires providing a color radiation-cooled optical thin film as described in any one of claims 1-3, and includes the following steps: Step 1: The thin film to be deposited has an asymmetric structure, with the structure: MDM'DM(A1A2)^s, where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods, s is a positive integer, M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. Step 2: Set the total number of layers in the thin film structure, the material used in each layer, the thickness of each layer, and the distribution between the layers according to the user's functional requirements; The first layer is the first metal layer M, the second layer is the dielectric layer D, the third layer is the second metal layer M', the fourth layer is the dielectric layer D, and the fifth layer is the first metal layer M; If s=1, then the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2; If s≥2, then the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2; repeat the structure of the sixth to seventh layers to set the eighth to the last layer; Step 3: Clean the surface of the substrate; Step 4: Grow the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating. Step 5: Separate the substrate from the first layer to obtain the prepared target film.

5. The method for preparing a colored radiation-cooled optical thin film as described in claim 4, characterized in that, In step 4, when growing the first absorption layer A1, the second absorption layer A2, and the dielectric layer D, electron beam evaporation ion-assisted deposition is used, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0. When growing the first metal layer M and the second metal layer M', resistance heating evaporation ion-assisted deposition is used, with the ion source voltage set to 350V and the electron gun oxygen flow rate set to 0.

6. The method for preparing a colored radiation-cooled optical thin film as described in claim 4, characterized in that, The substrate material is made of polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate, cellulose triacetate, polymethyl methacrylate, polycarbonate / polymethyl methacrylate composite material, polyimide, polypropylene, polyvinyl chloride, polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane elastomer, polytetrafluoroethylene, fluoroethyl propylene, or polydifluoroethylene. The substrate has a release layer material on its upper surface, which separates the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

7. A colored radiation-cooled optical thin film, characterized in that, The thin film comprises a structure stacked sequentially from bottom to top: (A2A1)^sMDM'DM(A1A2)^s. This thin film has a symmetrical structure centered on M', where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods (s is a positive integer), M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. M(A1A2)^s serves as an atmospheric window radiation film layer, achieving high absorption in the 8-13 μm wavelength range through intrinsic absorption and destructive interference effects. MDM'DM serves as a visible and near-infrared band modulation film layer, employing... A dual-FP cavity coupled symmetrical structure color film layer centered on coupling layer M' achieves high reflectivity in the 400-2500nm solar light band and adjusts the coupling degree of the dual-FP cavities by adjusting the thickness of M' in the 400-800nm ​​visible light range, which is manifested in the spectrum as adjusting the width of the absorption peak; the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; the thickness range of the first metal layer M is between 10-30nm; the thickness range of the second metal layer M' is between 10-50nm; and the thickness range of the dielectric layer D is between 55-150nm.

8. A method for preparing a colored radiation-cooled optical thin film, characterized in that, The method requires providing a color radiation-cooled optical thin film as described in any one of claims 7, comprising the following steps: Step 1: The thin film to be deposited has a symmetrical structure, with the structure: (A2A1)^sMDM'DM(A1A2)^s. The structure of this thin film is a symmetrical structure centered on M', where A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of stacking periods, s is a positive integer, M represents the first metal layer, D represents the dielectric layer, and M' represents the second metal layer. Step 2: Set the total number of layers in the thin film structure, the material used in each layer, the thickness of each layer, and the distribution between the layers according to the user's functional requirements; The i-th layer at the very center is the second metal layer M', the (i-1)-th layer is the dielectric layer D, the (i+1)-th layer is the dielectric layer D, the (i-2)-th layer is the first metal layer M, and the (i+2)-th layer is the first metal layer M. If s=1, then i=5; the first layer is the second absorption layer A2, the second layer is the first absorption layer A1; the eighth layer is the first absorption layer A1, and the ninth layer is the second absorption layer A2; If s≥2, then the first layer is the second absorption layer A2, and the second layer is the first absorption layer A1; repeat the structure from the first layer to the second layer to set the third layer to the (i-3)th layer; the (i+3)th layer to the last layer is symmetrical to the (i-3)th layer to the first layer; Step 3: Clean the surface of the substrate; Step 4: Grow the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating. Step 5: Separate the substrate from the first layer to obtain the prepared target film.

Images