Colorful radiation refrigeration optical film and preparation method thereof

Abstract

The invention discloses a colored radiation refrigeration optical thin film, which comprises a structure: MDM 'DM (A1A2) s which are sequentially stacked from bottom to top, the structure of the thin film is an asymmetric structure, A1 represents a first absorption layer, A2 represents a second absorption layer, s represents the number of stacking cycles, s is a positive integer, M represents a first metal layer, D represents a dielectric layer, and M' represents a second metal layer; m (A1A2) s is used as an atmospheric window radiation film layer, and MDM 'DM is used as a visible light and near-infrared band regulation and control film layer. The invention further discloses a preparation method of the colored radiation refrigeration optical thin film, and the colored radiation refrigeration optical thin film has the advantages of wide color gamut range adjustability, high saturation, low sunlight absorption and high emissivity of an atmospheric transparent window.

Description

Technical Field

[0001] The invention relates to the technical field of optical films, and in particular to a color radiation cooling optical film and a preparation method thereof. Background Art

[0002] As a new type of refrigeration technology, radiative cooling has a high emissivity in the atmospheric transparent window (8-13μm) by regulating the spectrum, and radiates heat into the universe through this window. It is worth noting that this refrigeration process does not require any energy consumption. This refrigeration method can be used to prepare clothing for human body heat regulation, or directly used on building exterior walls, combined with color for car paint, etc.

[0003] In order to reflect sunlight and reduce the absorption of solar thermal radiation, traditional radiative cooling films often have high reflective properties in the visible light band, so radiative cooling films always appear silvery white. However, in today's society, people's requirements for aesthetics are becoming more and more stringent, and the single silvery white color does not meet modern aesthetic standards. At the same time, because it always highly reflects visible light and appears silvery white, it will cause light pollution to a certain extent.

[0004] The patent with the publication number CN13791468B discloses a method for manufacturing a color radiation cooling film, which uses PET, PEN, etc. as a substrate layer, and uses a metal layer, a spacer layer, and a Bragg reflection layer to form a Tamm structure, and realizes high-quality factor selective absorption of visible light by exciting Tamm resonance at the interface of the metal layer and the spacer layer. The patent can obtain a radiation cooling film with good color rendering performance, but in addition to the above-mentioned metal layer, spacer layer, and Bragg reflection layer (where the Bragg reflection layer contains at least three layers), an external functional layer and a protective layer are also required to realize color radiation cooling, which is relatively complicated.

[0005] The patent with the publication number CN113234367B discloses a method for manufacturing a color radiation cooling film, which uses polyacrylate / water-based polyvinylidene fluoride resin, inorganic fillers and additives to form a radiation cooling film layer; polystyrene microspheres and polyacrylate / water-based polyvinylidene fluoride resin are used to construct a structural color layer. This method requires many types of organic compounds, and the preparation process is relatively complicated and environmentally unfriendly.

[0006] Patent CN202010898293.5 discloses a composite color radiation cooling film and its preparation method. The composite film uses a high molecular polymer as a substrate, and phase change microcapsules and pigments are doped in the substrate, and the composite film is prepared by electrospinning technology. This patent obtains the desired color by chemical means, and obtains different colors by doping different types of pigments, but the addition of pigments will bring more solar radiation absorption and reduce the efficiency of radiation cooling. At the same time, the light absorption of the pigment depends on the basic absorption characteristics of the doped material, which is difficult to freely and accurately regulate.

[0007] In order to address the above problems, it is of great significance to study a colorful radiative cooling film that can be widely used in daily life scenarios. Summary of the invention

[0008] In view of this, the purpose of the present invention is to provide a color radiation cooling optical film, which has the advantages of wide color gamut adjustability, higher saturation, low sunlight absorption, and high emissivity of the atmospheric transparent window.

[0009] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0010] The present invention provides a color radiation cooling optical film, which includes a structure stacked in sequence from bottom to top: MDM'DM(A1A2)^s, and the structure of the film is an asymmetric structure, wherein A1 represents a first absorption layer, A2 represents a second absorption layer, s represents the number of superposition periods, s is a positive integer, M represents a first metal layer, D represents a dielectric layer, and M' represents a second metal layer; M(A1A2)^s is used as an atmospheric window radiation film layer to achieve high absorption rate in the wavelength range of 8-13μm; MDM'DM is used as a visible light and near-infrared band regulating film layer, and a double FP cavity coupled symmetrical structural color film layer with a coupling layer M' as the center is adopted to achieve high reflectivity in the sunlight band of 400-2500nm and adjust the coupling degree of the double FP cavity in the visible light range of 400-800nm ​​by the thickness of M', which is manifested in the spectrum as adjusting the width of the absorption peak.

[0011] Furthermore, the reflectivity of the first metal layer M and the second metal layer M' in the wavelength range of 0.4-1.3 μm is greater than 80%, 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 in the wavelength range of 8-13 μm are between 0 and 3, 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] Further, 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 in the range of 10-30 nm;

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

[0017] The thickness of the dielectric layer D is in the range of 55-150 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, the superposition period number s=1. When the superposition period number s=1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; when the superposition period number s≥1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2000nm.

[0020] The present invention also provides a method for preparing a color radiation cooling optical film, which method requires providing the above-mentioned color radiation cooling optical film, and comprises the following steps:

[0021] Step 1, the film to be plated is an asymmetric structure, and its structure is: MDM'DM(A1A2)^s, wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition cycles, 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 of the 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, the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2;

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

[0026] Step 3, cleaning the surface of the substrate;

[0027] Step 4, growing a first layer on the upper surface of the substrate, and when the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and when the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing 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, when growing the first absorption layer A1, the second absorption layer A2 and the dielectric layer D in step 4, the growth is carried out by electron beam evaporation ion-assisted deposition, the voltage of the ion source is set to 350V, and the electron gun oxygen flow rate is set to 0; when growing the first metal layer M and the second metal layer M', the growth is carried out by resistance heating evaporation ion-assisted deposition, the voltage of the ion source is set to 350V, and the electron gun oxygen flow rate is set to 0.

[0030] Further, the material of the substrate is 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 polyvinyl difluoride;

[0031] The upper surface of the substrate has a release layer material, and the substrate and the first layer are separated by the release layer material; the release layer material is a fluoride or chloride that is easily soluble in water, or an organic material and an organic solvent that is soluble in water, and the organic solvent is polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride or fluoride.

[0032] The present invention also provides a color radiation cooling optical film, which includes a structure stacked in sequence from bottom to top: (A2A1)^sMDM'DM(A1A2)^s, and the structure of the film is a symmetrical structure with M' as the center, wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 is used as an atmospheric window radiation film layer to achieve high absorption rate in the wavelength range of 8-13μm; MDM'DM is used as a visible light and near-infrared band regulating film layer, and a double FP cavity coupled symmetrical structural color film layer with the coupling layer M' as the center is adopted to achieve high reflectivity in the sunlight band of 400-2500nm and adjust the coupling degree of the double FP cavity in the visible light range of 400-800nm ​​by the thickness of M', which is manifested in the spectrum as adjusting the width of the absorption peak.

[0033] The present invention also provides a method for preparing a color radiation cooling optical film, which method requires providing the above-mentioned color radiation cooling optical film, and comprises the following steps:

[0034] Step 1, the film to be plated is a symmetrical structure, and its structure is: (A2A1)^sMDM'DM(A1A2)^s, the structure of the film is a symmetrical structure centered on M', wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 of the 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 center is the second metal layer M', the i-1th layer is the dielectric layer D, the i+1th layer is the dielectric layer D, the i-2th layer is the first metal layer M, and the i+2th 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, the first layer is the second absorption layer A2, and the second layer is the first absorption layer A1; the structure of the first layer to the second layer is repeated to set the third layer to the i-3th layer; the i+3th to the last layer is symmetrical with the i-3th layer to the first layer;

[0039] Step 3, cleaning the surface of the substrate;

[0040] Step 4, growing a first layer on the upper surface of the substrate, and when the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and when the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing 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. The symmetrical or asymmetrical structure of the complementary MDM'DM double FP cavity is used as the visible light and near-infrared band regulating film layer to form an absorption band with adjustable width and depth while reflecting sunlight as much as possible, thereby obtaining a wider adjustable color gamut and higher saturation.

[0044] 2. By adopting the M(A1A2)^s structure, a high absorption rate at 8-13μm can be achieved with fewer film layers (3 layers are most preferred), thereby obtaining a better radiation effect.

[0045] 3. The structure is simple and can be easily expanded into a symmetrical color radiation cooling film. Moreover, the materials are all inorganic and do not need to be degraded, which is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[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 of the dual FP cavity coupling provided by the present invention.

[0049] Figure 3 This is a schematic diagram of the structure of the atmospheric window radiation film layer and the visible light and near-infrared band regulating film layer provided by the present invention, where the two films are coupled to form a color radiation cooling film.

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

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

[0052] Figure 6 This is a schematic diagram of the reflectivity of the remaining solar light bands (800-2500nm) of Example 1 provided by the present invention.

[0053] Figure 7 A schematic diagram of the absorbance in the atmospheric transparent window band (8-13 μm) of Example 1 provided by the present invention.

[0054] Figure 8 This is a schematic diagram of chromaticity coordinates of Example 1 provided by the present invention.

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

[0056] Fig.10 This is a schematic diagram of the reflectivity of the remaining sunlight bands (800-2500nm) of Example 2 provided by the present invention.

[0057] Fig.11 This is a schematic diagram of the absorbance in the atmospheric transparent window band (8-13 μm) of Example 2 provided by the present invention.

[0058] Fig.12 This is a schematic diagram of the two chromaticity coordinates of an embodiment provided by the present invention.

[0059] Fig.13 This is a schematic diagram of the reflectivity in the visible light band of Example 3 provided by the present invention.

[0060] Fig.14 This is a schematic diagram of the reflectivity of the remaining sunlight bands (800-2500nm) of Example 3 provided by the present invention.

[0061] Fig.15 This is a schematic diagram of the absorbance in the atmospheric transparent window band (8-13 μm) of Example 3 provided by the present invention.

[0062] Fig.16 This is a schematic diagram of three chromaticity coordinates of an embodiment provided by the present invention.

[0063] Fig.17 This is a schematic diagram of the reflectivity in the visible light band of Example 4 provided by the present invention.

[0064] Fig.18 This is a schematic diagram of the reflectivity of the remaining sunlight bands (800-2500nm) of Example 4 provided by the present invention.

[0065] Fig.19 This is a schematic diagram of the absorbance in the atmospheric transparent window band (8-13 μm) of Example 4 provided by the present invention.

[0066] Fig. 20 This is a schematic diagram of four chromaticity coordinates of an embodiment provided by the present invention.

[0067] Fig.21 This is a schematic diagram of the reflectivity in the visible light band of Example 4 provided by the present invention.

[0068] Fig. 22 This is a schematic diagram of the reflectivity of the remaining sunlight bands (800-2500nm) of Example 4 provided by the present invention.

[0069] Fig.23 This is a schematic diagram of the absorbance in the atmospheric transparent window band (8-13 μm) of Example 4 provided by the present invention.

[0070] Fig.24 This is a schematic diagram of four chromaticity coordinates of an embodiment provided by the present invention.

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

[0072] Fig.26 The present invention provides a schematic diagram of the process flow. DETAILED DESCRIPTION

[0073] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention. Similarly, the following examples are only partial embodiments of the present invention rather than all embodiments, and all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0074] The design ideas of the present invention are as follows:

[0075] In order to realize the high emissivity of the atmospheric window and the regulation of visible light, the present invention divides the film layer into two parts for explanation, including: the atmospheric window radiation film layer and the visible light and near infrared band regulation film layer.

[0076] 1. Atmospheric window radiation film

[0077] For the design of the atmospheric window radiation film layer, it is necessary to have a high absorptivity (emissivity) in the atmospheric transparent window (8-13μm) and minimize the impact on the visible light band. Therefore, it is necessary to select a material that is transparent to visible light and has a high extinction coefficient at 8-13μm for design. Based on the above spectral requirements, the present 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 superposition periods) to achieve a high absorptivity at 8-13μm. Figure 1As shown (MA1A2 is the most preferred, i.e. s=1), the present invention mainly absorbs through the intrinsic absorption of the material and the destructive interference effect, so that the structure has a higher absorption rate at 8-13μm. Among them, the thickness of the first metal layer M is 10-30nm, which participates in the formation of the reflector of the resonant cavity, and has a balanced reflectivity and color saturation. When s is 1, the thickness of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; when s>1, the thickness of the first absorption layer A1 and the second absorption layer A2 is reduced as needed to meet the demand for high absorption rate. The reflectivity of the first metal layer M at 0.4-1.3μm is greater than 80%. The material of the metal layer includes one or more of Ag, Au, Al, and Cu, and Ag is the most preferred. In the range of 8-13μm, the extinction coefficient of the first absorption layer A1 and the second absorption layer A2 ranges from 0-3, and the first absorption layer A1 and the second absorption layer A2 are different materials. The thickness of the first absorption layer A1 and the second absorption layer A2 is different. The first absorption layer A1 and the second absorption layer A2 can be two different kinds of absorption materials, such as TiO2, SiO2, Al2O3, Si3N4, or HfO2, depending on the period s. Considering the simplicity of the structure, when s=1, TiO2 is preferably used as the first absorption layer A1 and SiO2 is preferably used as the second absorption layer A2.

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

[0079] For the design of the visible light and near-infrared band regulating film layer, the sunlight band (0.4-2.5μm) should be reflected as much as possible to reduce the absorption of heat, so the introduction of metal materials with high reflectivity is considered first. The full high reflection in the sunlight band will cause the radiation cooling film to always appear silvery white. The single silver-white color does not meet the modern aesthetic standards, and it may also cause light pollution during the promotion and application process. In the above context, we construct the FP cavity on a single metal reflective layer and design a complementary color structure, which can selectively absorb part of the visible light band while having little effect on its high reflectivity characteristics in the entire sunlight band. At the same time, taking into account the symmetry and color saturation of the structure, a symmetrical structural color film layer is designed in the form of dual FP cavity coupling centered on the coupling layer M', that is, the MDM'DM structure. Compared with the single FP cavity, the MDM'DM structure can obtain a wider adjustable color gamut and better color saturation, such as Figure 2As shown. While the structure has high reflectivity in the sunlight band of 400-2500nm, it can also change the coupling degree of the two resonant cavities in the visible light range of 400-800nm ​​by changing the thickness of the second metal layer M' (the thickness control range is 15-50nm, within which a relatively obvious mode splitting can occur, which is conducive to the formation of a wider absorption band. When the thickness is less than 15nm, the mode splitting is significant, and the two resonance peaks are completely separated, forming two absorption bands, which is not conducive to the formation of high-saturation colors. When the thickness is greater than 50nm, the coupling strength is weakened, the mode is gradually decoupled, and the two resonance peaks merge into one to form a narrow-band absorption valley, which is also not conducive to the formation of high-saturation colors.) The width of the absorption peak can be adjusted in the spectrum, and the color produced can be adjusted by simultaneously changing the thickness of the dielectric layer D (the thickness control range is 55-113nm, within which the absorption band can be controlled to be located in the visible light band to form complementary colors. If the thickness is not within this range, the absorption valley is not within the visible light range and no color can be produced).

[0080] The following is an analysis of the dual-resonance cavity coupling principle. For a single resonant cavity, the 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 of the resonant mode (integer). λ represents the resonant wavelength. For two independent resonant cavities, assume that their natural resonant frequencies are:

[0083]

[0084] Where c is the speed of light in vacuum, about 3*10 8 m / s. At this time, the two resonant cavities are independent of each other, and light will not propagate between the two resonant cavities. When the two resonant cavities are coupled (a common metal layer is used for coupling in the present invention), light can propagate and interact between the two resonant cavities. This coupling effect changes the resonant condition of the system, causing the original single resonant mode to split into two new modes. The resonant frequency f of the coupled system ± It can be expressed as:

[0085]

[0086] Among them, f ± They represent the frequencies of the symmetric and antisymmetric modes after mode splitting, and k represents the coupling strength of the two resonant cavities. 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] Wherein, T is the transmittance of the metal coupling layer (the attenuation of light in the metal layer follows the Beer-Lambert law), α is the absorption coefficient (for the present invention, metal is used as the coupling layer, Where μ is the extinction coefficient of the material used in the coupling layer). After two resonant cavities with the same eigenfrequency are coupled through a common metal layer and mode splitting occurs, two discrete resonance peaks can be generated in the spectrum, and their frequency interval and wavelength interval are:

[0089] Δf=2k,

[0090] The present invention is used as an example to illustrate that according to the above theory, the coupling strength k is adjusted to a smaller value by controlling the thickness of the intermediate metal coupling layer, so that the wavelength interval between the two resonance peaks generated by mode splitting is smaller, thus obtaining a larger absorption band. By simultaneously controlling the optical thickness of the two resonant cavities, the position of the resonance peak can be adjusted.

[0091] In this way, a wide color gamut tunable, high-saturation structural color film can be obtained under the condition of reflecting most of the sunlight. Wherein, the reflectivity of the first metal layer M and the second metal layer M' at 0.4-1.3μm is greater than 80%. The materials of the first metal layer M and the second metal layer M' include one or more of Ag, Au, Al, and Cu. Considering the reflectivity, Ag is the most preferred. 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. Based on the consideration of high refractive index, LaTiO3 is preferred.

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

[0093] The above-mentioned atmospheric window radiation film layer and the visible light and near-infrared band regulating film layer are coupled through the metal layer M to form a color radiation cooling film, such as Figure 3 As shown. This structure can have a high atmospheric window emissivity (greater than 85%), a high average reflectivity in the sunlight band (greater than 90%), and a high saturation color display. In summary, the most preferred are: TiO2 as A1, SiO2 as A2, Ag as M and M', and LaTiO3 as D. At the same time, it can be observed that since the color structure MDM'DM is symmetrical at the beginning of the design, it is very easy to expand the above-mentioned radiation cooling film into a symmetrical film without causing the structure to become overly complicated. The expanded structure is as follows Figure 4As shown. For symmetrical film structures, the incident light from the front and back of the film system has the same spectral characteristics, and then some processes can be used to make it into a micro-element radiation cooling film, and then prepared into a coating material, and applied to the surface of vehicles, buildings, etc. by spraying, scraping, brushing, etc. The above methods can be widely used on irregular surfaces of objects, without being restricted by the size, shape, etc. of the coating process. In order to facilitate intuitive understanding, a brief technical solution flow chart is shown below Fig.25 shown.

[0094] Compared with the existing technology, the color radiation cooling film provided by the present invention is composed of an atmospheric window radiation film layer and a visible light and near infrared band regulation film layer. It can achieve precise control of the spectrum in a simple structure, has better color controllability, and can be easily expanded into a symmetrical color radiation cooling film. In addition, the raw materials used are all inorganic, do not need to be degraded, and are environmentally friendly.

[0095] Solution 1:

[0096] A color radiation cooling optical film, the film comprises a structure stacked in sequence from bottom to top: MDM'DM(A1A2)^s, the structure of the film is an asymmetric structure, wherein A1 represents a first absorption layer, A2 represents a second absorption layer, s represents the number of superposition periods, s is a positive integer, M represents a first metal layer, D represents a dielectric layer, and M' represents a second metal layer; M(A1A2)^s is used as an atmospheric window radiation film layer to achieve high absorption rate in the wavelength range of 8-13μm; MDM'DM is used as a visible light and near-infrared band regulating film layer, and a double FP cavity coupled symmetrical structural color film layer with a coupling layer M' as the center is adopted to achieve high reflectivity in the sunlight band of 400-2500nm and adjust the coupling degree of the double FP cavity in the visible light range of 400-800nm ​​by adjusting the thickness of M', 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' in the wavelength range of 0.4-1.3 μm is greater than 80%, 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 in the wavelength range of 8-13 μm are between 0 and 3, 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 in the range of 400-2500 nm;

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

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

[0103] The thickness of the dielectric layer D is in the range of 55-150 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 superposition period number s=1. When the superposition period number s=1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; when the superposition period number s≥1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2000nm.

[0106] Option 2:

[0107] The present invention also provides a method for preparing a color radiation cooling optical film, which method requires providing the above-mentioned color radiation cooling optical film, and comprises the following steps:

[0108] Step 1, the film to be plated is an asymmetric structure, and its structure is: MDM'DM(A1A2)^s, wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition cycles, 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 of the 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, the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2;

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

[0113] Step 3, cleaning the surface of the substrate;

[0114] Step 4, growing a first layer on the upper surface of the substrate, and when the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and when the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing 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, when growing the first absorption layer A1, the second absorption layer A2 and the dielectric layer D in step 4, electron beam evaporation ion-assisted deposition is used for growth, the voltage of the ion source is set to 350V, and the oxygen flow rate of the electron gun is 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, the voltage of the ion source is set to 350V, and the oxygen flow rate of the electron gun is set to 0.

[0117] The material of the substrate is polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate (PET), triacetyl cellulose (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 difluoride (PVDF);

[0118] The upper surface of the substrate has a release layer material, and the substrate and the first layer are separated by the release layer material; the release layer material is a fluoride or chloride that is easily soluble in water, or an organic material and an organic solvent that is soluble in water, and the organic solvent is polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride or fluoride.

[0119] Option 3:

[0120] The present invention also provides a color radiation cooling optical film, which includes a structure stacked in sequence from bottom to top: (A2A1)^sMDM'DM(A1A2)^s, and the structure of the film is a symmetrical structure with M' as the center, wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 is used as an atmospheric window radiation film layer to achieve high absorption rate in the wavelength range of 8-13μm; MDM'DM is used as a visible light and near-infrared band regulating film layer, and a double FP cavity coupled symmetrical structural color film layer with the coupling layer M' as the center is adopted to achieve high reflectivity in the sunlight band of 400-2500nm and adjust the coupling degree of the double FP cavity in the visible light range of 400-800nm ​​by the thickness of M', which is manifested in the spectrum as adjusting the width of the absorption peak.

[0121] Preferably, the reflectivity of the first metal layer M and the second metal layer M' in the wavelength range of 0.4-1.3 μm is greater than 80%, 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 in the wavelength range of 8-13 μm are between 0 and 3, 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 in the range of 400-2500 nm;

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

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

[0127] The thickness of the dielectric layer D is in the range of 55-150 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 superposition period number s=1. When the superposition period number s=1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; when the superposition period number s≥1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2000nm.

[0130] Option 4:

[0131] The present invention also provides a method for preparing a color radiation cooling optical film, which method requires providing the above-mentioned color radiation cooling optical film, and comprises the following steps:

[0132] Step 1, the film to be plated is a symmetrical structure, and its structure is: (A2A1)^sMDM'DM(A1A2)^s, the structure of the film is a symmetrical structure centered on M', wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 of the 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 center is the second metal layer M', the i-1th layer is the dielectric layer D, the i+1th layer is the dielectric layer D, the i-2th layer is the first metal layer M, and the i+2th 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, the first layer is the second absorption layer A2, and the second layer is the first absorption layer A1; the structure of the first layer to the second layer is repeated to set the third layer to the i-3th layer; the i+3th to the last layer is symmetrical with the i-3th layer to the first layer;

[0137] Step 3, cleaning the surface of the substrate;

[0138] Step 4, growing a first layer on the upper surface of the substrate, and when the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and when the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing 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, when growing the first absorption layer A1, the second absorption layer A2 and the dielectric layer D in step 4, electron beam evaporation ion-assisted deposition is used for growth, the voltage of the ion source is set to 350V, and the oxygen flow rate of the electron gun is 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, the voltage of the ion source is set to 350V, and the oxygen flow rate of the electron gun is set to 0.

[0141] Preferably, the material of the substrate is polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate (PET), triacetyl cellulose (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 difluoride (PVDF);

[0142] The upper surface of the substrate has a release layer material, and the substrate and the first layer are separated by the release layer material; the release layer material is a fluoride or chloride that is easily soluble in water, or an organic material and an organic solvent that is soluble in water, and the organic solvent is polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride or fluoride.

[0143] In this specific embodiment, the preparation of the thin film can be achieved by physical vapor deposition (PVD) methods, including ion beam sputtering deposition (IBS), magnetron sputtering deposition (MS), electron beam evaporation (EB) or electron beam evaporation ion assisted deposition (EBD-IAD) and other different technologies. In addition, the thin film can also be prepared by chemical vapor deposition (CVD) methods or pearlescent thin film liquid phase coating methods.

[0144] In order to facilitate explanation and description, as well as consideration of the multilayer film process in actual preparation, the technical method of electron beam evaporation ion assisted deposition (EBD-IAD) is now used to illustrate the process preparation. The basic principle of this technology is as follows:

[0145] 1. Generate a high-energy electron beam with adjustable power through an electron gun, guide and accelerate the electron beam to the target material through electric and magnetic fields. The electron gun generally includes a hot cathode that emits electrons (usually a heated tungsten filament) and an anode that accelerates the electrons.

[0146] 2. The high-energy electron beam hits the target material, converting its energy into heat energy, heating the target material to the evaporation temperature.

[0147] 3. The evaporated material atoms or molecules fly in a vacuum to the surface of the substrate, where they condense to form a thin film. The ion beam adds energy to the outermost atomic layer when forming a thin film, thereby affecting the hardness, density and surface morphology of the microstructure to achieve better bonding and adhesion. The use of an ion source can effectively improve the quality of the film, including density, hardness and adhesion, while better controlling the surface texture and microstructure. Although the ion beam only barely penetrates the atoms on the top surface of the growing film, the ions released by the ion beam make the film denser because the microcrystals being formed are more compactly arranged. At the same time, this process takes place in a vacuum, so the evaporated atoms or molecules basically do not interact with other gas molecules during flight, which helps to form high-quality films.

[0148] However, in the actual preparation process, more factors need to be considered:

[0149] 1. It is necessary to ensure that the vacuum coating machine has stable working conditions, such as ensuring the working conditions of the electron gun and ion source, the working conditions of each mechanical pump, the cleanliness of the vacuum chamber, and the working conditions of the film thickness controller.

[0150] 2. Preparation before coating, such as input of film system, placement of coating materials, selection and wiping of coating substrate.

[0151] 3. Vacuum and pre-melt materials (if necessary).

[0152] 4. Prepare the target film by evaporation.

[0153] by Figure 3 The structures shown are preferably respectively: TiO2 as A1, SiO2 as A2, Ag as M and M', and LaTiO3 as D as examples for explanation.

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

[0155] S2. On the above substrate, the first layer of Ag is grown by resistive 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, electron beam evaporation (using high-energy electron beams to bombard the evaporation material, causing it to be locally heated and vaporized into steam. Electron beams can produce very high temperatures (>3000°C), which is suitable for high melting point materials such as SiO2, TiO2, etc. The evaporation rate and deposition thickness can be precisely controlled by the electron beam energy) is used to grow the second layer of LaTiO3 by ion-assisted deposition. 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, resistive heating evaporation (electric current is passed through a high-resistance heating wire, such as a tungsten boat or a molybdenum boat, to heat the evaporated material to vaporization. It is suitable for low melting point materials such as Ag, Al, and Au, which are suitable for resistive heating evaporation because they do not require excessively high temperatures and avoid material loss or oxidation caused by excessive heating) is used to grow the third layer of Ag by 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 third layer, a fourth layer of LaTiO3 is grown by electron beam evaporation and ion-assisted deposition, with the ion source voltage set to 350 V and the electron gun oxygen flow rate set to 0.

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

[0160] S7. On the fifth layer, the sixth layer of TiO2 is grown by electron beam evaporation ion assisted deposition (pre-melting is required), the ion source voltage is set to 350V, and the oxygen flow rate of the electron gun is controlled (the raw material for preparing TiO2 is Ti3O5, which is closer to the target film chemical formula than metallic titanium or other titanium oxides, such as TiO, and reduces the need for additional oxidation. The evaporation of TiO2 requires extremely high temperatures, and only high-power electron beam evaporation equipment or laser evaporation equipment can meet the requirements. When TiO2 evaporates at high temperatures, uneven evaporation and melting may occur on the surface of the material, resulting in splashing on the surface of the evaporation source, affecting the uniformity and optical quality of the film), so that the vacuum degree is 2.2-2.3*10 -3 Between Pa.

[0161] S7. On the sixth layer, the seventh 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 is set to 0.

[0162] For intuitive and convenient explanation, the simplified process flow chart is as follows Fig.26 shown.

[0163] In order to make the purpose, technical solution and advantages of the present invention more clear, the following will provide drawings and embodiments of an asymmetric radiant cooling film and a symmetric radiant cooling film, respectively, to further describe and demonstrate the present invention in detail.

[0164] Example 1

[0165] The basic structure of a color radiation cooling film is as follows: Figure 3As shown, the total number of layers of the color radiation cooling film is only 7, among which 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] By adjusting the thickness of the M and M' layers, the embodiment has an average reflectivity of 92.6% in the sunlight band (400-2500nm), which can reflect most of the solar radiation, thereby reducing heat absorption. Figure 5 As shown, the rest of the solar wavelength band (800-2500nm) is as follows Figure 6 By adjusting the thickness of the A1 and A2 layers, the average absorptivity (emissivity) in the atmospheric transparent window band (8-13 μm) is 88.25%. Figure 7 As shown, it has good radiation ability. 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, and the absorption band is controlled to be located in the red band. The remaining bands still maintain high reflection, and the blue band and the green band obtained by reflection are superimposed to obtain a cyan radiation cooling film. The high reflectivity of the wide spectrum in the visible light band not only realizes the superposition of colors, but also reflects most of the solar radiation. The chromaticity coordinates of this embodiment are (0.2384, 0.3249), as shown in FIG. Figure 8 shown.

[0169] Example 2

[0170] The basic structure of a color radiation cooling film is as follows: Figure 3 As shown, the total number of layers of the color radiation cooling film is only 7, among which 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 adjusts the thickness of the M and M' layers to achieve an average reflectivity of 91% in the solar band (400-2500nm), which can reflect most of the solar radiation, thereby reducing heat absorption. Fig. 9 As shown, the rest of the solar wavelength band (800-2500nm) is as follows Fig.10 By adjusting the thickness of the A1 and A2 layers, the average absorptivity (emissivity) in the atmospheric transparent window band (8-13 μm) is 88.25%. Fig.11As shown, it has good radiation ability. 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, so that the absorption band is controlled to be located in the green band. The remaining bands still maintain high reflection, and the blue band and the red band obtained by reflection are superimposed to obtain a magenta radiation cooling film. The high reflectivity of the wide spectrum in the visible light band not only realizes the superposition of colors, but also reflects most of the solar radiation. The chromaticity coordinates of this embodiment are (0.3743, 0.2398), as shown in FIG. Fig.12 shown.

[0173] Example 3

[0174] The basic structure of a color radiation cooling film is as follows: Figure 3 As shown, the total number of layers of the color radiation cooling film is only 7, among which 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 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] By adjusting the thickness of the M and M' layers, the embodiment has an average reflectivity of 93% in the solar light band (400-2500nm), which can reflect most of the solar radiation, thereby reducing heat absorption. Fig.13 As shown, the rest of the solar wavelength band (800-2500nm) is as follows Fig.14 By adjusting the thickness of the A1 and A2 layers, the average absorptivity (emissivity) in the atmospheric transparent window band (8-13 μm) is 88.23%. Fig.15 As shown, it has good radiation ability. 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, so that the absorption band is located in the blue band. The remaining bands still maintain high reflection, and the green band and the red band obtained by reflection are superimposed to obtain a yellow radiation cooling film. The high reflectivity of the wide spectrum in the visible light band not only realizes the superposition of colors, but also reflects most of the solar radiation. The chromaticity coordinates of this embodiment are (0.4115, 0.4724), and the radiation cooling film is yellow. Fig.16 shown.

[0177] Example 4

[0178] The basic structure of a symmetrical color radiation cooling film is as follows: Figure 4 As shown, by simply expanding two radiation layers, the asymmetric color radiation cooling film is derived into a symmetric one. The total number of layers of the symmetric color radiation cooling film is only 9, where A1 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 adjusts the thickness of the M and M' layers to achieve an average reflectivity of 75% in the solar band (400-2500nm), which can reflect most of the solar radiation, thereby reducing heat absorption. Fig.17 As shown, the rest of the solar wavelength band (800-2500nm) is as follows Fig.18 By adjusting the thickness of the A1 and A2 layers, the average absorptivity (emissivity) in the atmospheric transparent window band (8-13 μm) is 88.467%. Fig.19 As shown, it has good radiation ability. 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, that is, the color is changed. Compared with magenta, this embodiment reflects more blue, making this embodiment appear purple. The chromaticity coordinates of this embodiment are (0.2954, 0.2223), and the radiation cooling film is purple, as shown in FIG. Fig. 20 shown.

[0182] Example 5

[0183] The basic structure of a symmetrical color radiation cooling film is as follows: Figure 4 As shown, by simply expanding two radiation layers, the asymmetric color radiation cooling film is derived into a symmetric one. The total number of layers of the symmetric color radiation cooling film is only 9, among which A1 is selected as Al2O3, A2 is selected as SiO2, M and M' are selected as Al, and D is selected 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] By adjusting the thickness of the M and M' layers, the embodiment has an average reflectivity of 90.36% in the solar light band (400-2500nm), which can reflect most of the solar radiation, thereby reducing heat absorption. Fig.21 As shown, the rest of the solar wavelength band (800-2500nm) is as follows Fig. 22 By adjusting the thickness of the A1 and A2 layers, the average absorptivity (emissivity) in the atmospheric transparent window band (8-13 μm) is 81.381%. Fig.23As shown, it has good radiation ability. 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, so that it is in the green band and the yellow band. The sky blue color is obtained by superimposing the reflected blue light and part of the green light. The high reflectivity of the wide spectrum in the visible light band not only realizes the superposition of colors, but also reflects most of the solar radiation. The chromaticity coordinates of this embodiment are (0.2098, 0.2367), and the radiation cooling film is sky blue. Fig.24 shown.

[0186] The above descriptions are only some embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any equivalent device or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A color radiation cooling optical film, characterized in that: The film includes a structure stacked in sequence from bottom to top: MDM'DM(A1A2)^s. The structure of the film is an asymmetric structure, wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 is used as an atmospheric window radiation film layer to achieve high absorption rate in the wavelength range of 8-13μm; MDM'DM is used as a visible light and near-infrared band regulating film layer, and adopts a double FP cavity coupled symmetrical structural color film layer centered on the coupling layer M' to achieve high reflectivity in the sunlight band of 400-2500nm and adjust the coupling degree of the double FP cavity in the visible light range of 400-800nm ​​by adjusting the thickness of M', which is manifested in the spectrum as adjusting the width of the absorption peak.

2. The color radiation cooling optical film according to claim 1, characterized in that: The reflectivity of the first metal layer M and the second metal layer M' in the wavelength range of 0.4-1.3 μm is greater than 80%, 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 in the wavelength range of 8-13 μm are between 0 and 3, 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 color radiation cooling optical film according to claim 2, characterized in that: The thickness of the first absorption layer A1 and the second absorption layer A2 ranges from 400 to 2500 nm; The thickness of the first metal layer M is in the range of 10-30 nm; The thickness of the second metal layer M' is in the range of 10-50 nm; The thickness of the dielectric layer D is in the range of 55-150 nm.

4. The color radiation cooling optical film according to claim 3, characterized in that: The first absorption layer A1 and the second absorption layer A2 are made of different materials and have different thicknesses.

5. The color radiation cooling optical film according to claim 1, characterized in that: The superposition period number s=1. When the superposition period number s=1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2500nm; when the superposition period number s≥1, the thickness range of the first absorption layer A1 and the second absorption layer A2 is between 400-2000nm.

6. A method for preparing a color radiation cooling optical film, characterized in that: The method requires providing a color radiation cooling optical film as described in any one of claims 1 to 5, comprising the following steps: Step 1, the film to be plated is an asymmetric structure, and its structure is: MDM'DM(A1A2)^s, wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition cycles, 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 of the 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; 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, the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2; If s≥2, the sixth layer is the first absorption layer A1, and the seventh layer is the second absorption layer A2; the structure of the sixth to seventh layers is repeated to set the eighth to last layers; Step 3, cleaning the surface of the substrate; Step 4, growing a first layer on the upper surface of the substrate, and when the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and when the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing 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.

7. The method for preparing a color radiation cooling optical film according to claim 6, characterized in that: When growing the first absorption layer A1, the second absorption layer A2 and the dielectric layer D in the step 4, the growth is carried out by electron beam evaporation ion-assisted deposition, the voltage of the ion source is set to 350V, and the electron gun oxygen flow rate is set to 0; when growing the first metal layer M and the second metal layer M', the growth is carried out by resistance heating evaporation ion-assisted deposition, the voltage of the ion source is set to 350V, and the electron gun oxygen flow rate is set to 0.

8. The method for preparing a color radiation cooling optical film according to claim 6, characterized in that: The substrate 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 polyvinyl difluoride; The upper surface of the substrate has a release layer material, and the substrate and the first layer are separated by the release layer material; the release layer material is a fluoride or chloride that is easily soluble in water, or an organic material and an organic solvent that is soluble in water, and the organic solvent is polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride or fluoride.

9. A color radiation cooling optical film, characterized in that: The film includes a structure stacked in sequence from bottom to top: (A2A1)^sMDM'DM(A1A2)^s, and the structure of the film is a symmetrical structure centered on M', wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 is used as an atmospheric window radiation film layer to achieve high absorption rate in the wavelength range of 8-13μm; MDM'DM is used as a visible light and near-infrared band regulating film layer, and a double FP cavity coupled symmetrical structural color film layer centered on the coupling layer M' is adopted to achieve high reflectivity in the sunlight band of 400-2500nm and adjust the coupling degree of the double FP cavity in the visible light range of 400-800nm ​​by adjusting the thickness of M', which is manifested in the spectrum as adjusting the width of the absorption peak.

10. A method for preparing a color radiation cooling optical film, characterized in that: The method needs to provide a color radiation cooling optical film as claimed in any one of claims 9, comprising the following steps: Step 1, the film to be plated is a symmetrical structure, and its structure is: (A2A1)^sMDM'DM(A1A2)^s, the structure of the film is a symmetrical structure centered on M', wherein A1 represents the first absorption layer, A2 represents the second absorption layer, s represents the number of superposition 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 of the 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; The i-th layer at the center is the second metal layer M', the i-1th layer is the dielectric layer D, the i+1th layer is the dielectric layer D, the i-2th layer is the first metal layer M, and the i+2th 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, the first layer is the second absorption layer A2, and the second layer is the first absorption layer A1; the structure of the first layer to the second layer is repeated to set the third layer to the i-3th layer; the i+3th to the last layer is symmetrical with the i-3th layer to the first layer; Step 3, cleaning the surface of the substrate; Step 4, growing a first layer on the upper surface of the substrate, and when the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and when the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing 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