Structural color film for realizing cooling function based on Fano resonance and preparation method thereof

Abstract

The invention discloses a structural color film for realizing a cooling function based on Fano resonance, the film comprises structures M1DM2AL (HL) s which are sequentially stacked from bottom to top, the structure of the film is an asymmetric structure, M1 represents a first metal layer, M2 represents a second metal layer, D represents a first dielectric layer, A represents an absorption layer, L represents a low-refractive-index dielectric layer, and M represents a first dielectric layer. H represents a high-refractive-index dielectric layer; s represents the number of repeated stacking times, and s is a positive integer; the M1DM2 structure is used as a discrete state, the M2A is used as a first continuous state, and the L (HL) s is used as a second continuous state. The invention further discloses a preparation method of the structural color film capable of achieving the cooling function based on Fano resonance, high-brightness, high-purity and wide-color-gamut structural color is achieved, and meanwhile it is guaranteed that near-infrared high reflection is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical films, and in particular to a structural color film that realizes a cooling function based on Fano resonance and a preparation method thereof. Background Art

[0002] Structural color is a color phenomenon originating from the microstructure of an object. It produces physical effects such as interference, diffraction and scattering of light of different frequencies through the microstructure, so that the light that finally enters the human eye presents a specific spectral power distribution. Compared with traditional coloring methods such as organic dyes and chemical pigments, structural colors have obvious advantages in purity, brightness, resolution, service life, environmental protection and safety, etc., so they have important application value in the fields of optical imaging / display / detection devices, anti-counterfeiting, car films, color decoration, optical filters, etc. So far, researchers have discussed a variety of different resonance mechanisms to produce structural colors, such as guided mode resonance (GMR), plasma resonance (SPR), Mie resonance, etc. However, the preparation of the above structural colors often involves complex nanoscale patterns, which has the disadvantages of high cost, complex process and long time for large-scale and large-area applications. In contrast, planar thin film structural colors without photolithography provide a simple color generation scheme, which is also the preferred scheme for realizing structural colors in the industrial field.

[0003] In recent years, researchers in the field of color have proposed many excellent design and preparation schemes, including (HL) n Repeated periodic structures of high and low refractive indices, asymmetric Fabry-Perot (FP) cavities, and structures using single or composite absorption layers, etc. For example, patent CN116540331A designs a thin-film structural color structure of stacked high and low refractive index materials, and uses all-dielectric materials for the design of reflective structural colors. The number of film layers and the ratio of high and low refractive indices determine the reflectivity and reflection bandwidth. Patent CN117930411A designs a red-based thin-film structural color structure based on an asymmetric FP cavity. By keeping the structure and materials unchanged and fine-tuning the thickness of the film layer, red with different saturations can be obtained.

[0004] However, the study of layered thin film structural colors with high brightness, high purity and wide color gamut characteristics is still a difficult task. In 1865, Fano Hugo proposed the concept of Fano resonance to explain the quantum interference phenomenon between electrons in rare gas atoms. Different from the Lorentz linearity formed by the traditional resonant cavity structure, the linearity generated by Fano resonance presents antisymmetric or asymmetric characteristics, which can form a peak and a valley at the same time in a shorter frequency range, and has a narrower spectral bandwidth. In color science, this means better saturation.

[0005] There are three forms of heat transmission: radiation, convection and conduction. The heat transmission from the sun to the earth is radiation. Objects are heated by radiation, and then convection and conduction are formed between them. The composition of sunlight includes 5% ultraviolet rays (wavelength 100nm-400nm), 51% infrared rays (wavelength 700nm-2400nm), and 44% visible light (wavelength 380nm-800nm). For the solar energy reaching the earth's surface, more than 50% is brought by infrared light. Although infrared light is not visible, it is the main source of heat. Therefore, the cooling effect can be achieved through high reflection of near-infrared.

[0006] At present, in the research and development of cooling films, few studies have combined structural color technology with it. For example, patent CN109291776A designed a car cooling film, which absorbs the heat in the car during phase change by phase change materials, thereby reducing the temperature inside the car. Patent CN115710780A designed a sunshade and cooling film through electrospinning, and its average light reflectivity reached more than 80% in the wavelength range of 300nm to 2500nm. Although the above-mentioned film has achieved a cooling effect, it has certain limitations in application. Therefore, a film structure that has high brightness, high purity and wide color gamut structural color and near-infrared high reflection has become one of the important issues that need to be solved urgently. In order to achieve the cooling effect while achieving structural color, it is necessary to adopt new design methods and optimization methods to design a high-brightness, high-purity, wide color gamut structural color film with cooling function. Summary of the invention

[0007] In view of this, the purpose of the present invention is to propose a structural color film based on Fano resonance to achieve a cooling function, adopt a Fano structure to achieve the design of a structural color film with high near-infrared reflection, and optimize it according to the color standard chromaticity coordinates, while achieving high-brightness, high-purity and wide color gamut structural colors, ensuring high reflection in the near-infrared.

[0008] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0009] The present invention provides a structural color film for realizing a cooling function based on Fano resonance. The film comprises a structure stacked in sequence from bottom to top: M1DM2AL(HL)^s. The structure of the film is an asymmetric structure, wherein M1 represents a first metal layer, M2 represents a second metal layer, D represents a first dielectric layer, A represents an absorption layer, L represents a low refractive index dielectric layer, and H represents a high refractive index dielectric layer; s represents the number of repeated stacking times, and s is a positive integer; the M1DM2 structure is used as a discrete state, M2A is used as a first continuous state, and L(HL)^s is used as a second continuous state.

[0010] Furthermore, the material of the first metal layer M1 and the second metal layer M2 is one of Ag, Ti, Al, Au and Cu.

[0011] Furthermore, the material of the first dielectric layer D is one or a mixture of at least two of MgF2, SiO2, TiO2, Al F3, CeF3, LaF3, Na3AlF6, NdF3, BaF2, CaF2, LiF, Ta2O5, HfO2, ZrO2, Nb2O5, La2Ti2O7, Y2O3, ZnS, Si3N4, Bi2O3, CeO2, Cr2O3, MgO, Nd2O3, ZnO and Al2O3.

[0012] Furthermore, the material of the absorption layer is one of Ni, Ti, Cr, Fe2O3, Ge, single crystal silicon, polycrystalline silicon, Sb2S3, Sb2Se3, VO2, Ge2Sb2Te5, Ge2Sb2Se4Te1 and GeTe.

[0013] Furthermore, the material of the high refractive index medium layer H is one of Ta2O5, TiO2, HfO2, ZrO2, Nb2O5, La2Ti2O7, Y2O3, ZnS, Si3N4, Bi2O3, CeO2, Cr2O3, MgO, Nd2O3 and ZnO; the material of the low refractive index medium layer L is one of MgF2, SiO2, Al2O3, Al F3, CeF3, LaF3, Na3Al F6, NdF3, BaF2, CaF2 and LiF.

[0014] Furthermore, the thickness of the first metal layer M1 is above 100 nm;

[0015] The thickness of the second metal layer M2 is in the range of 5-35 nm;

[0016] The thickness of the first dielectric layer D is in the range of 5-1000 nm;

[0017] The thickness of the absorption layer A ranges from 1 to 30 nm;

[0018] The thickness of the low refractive index medium layer L is in the range of 5-1000 nm;

[0019] The thickness of the high refractive index medium layer H is in the range of 5-1000 nm.

[0020] Furthermore, the number of repeated stacking times s=1 or 2.

[0021] The present invention also provides a method for preparing a structural color film that realizes a cooling function based on Fano resonance. The method needs to provide a structural color film that realizes a cooling function based on Fano resonance as described above, and specifically comprises the following steps:

[0022] Step 1, the film to be plated is an asymmetric structure, and its structure is: M1DM2AL(HL)^s, the structure of the film is an asymmetric structure, wherein M1 represents the first metal layer, M2 represents the second metal layer, D represents the first dielectric layer, A represents the absorption layer, L represents the low refractive index dielectric layer, and H represents the high refractive index dielectric layer; s represents the number of repeated stacking, and s is a positive integer; the M1DM2 structure is used as a discrete state, M2A is used as a first continuous state, and L(HL)^s is used as a second continuous state;

[0023] Step 2: according to the functional requirements of the user, 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 are set, so that the film presents the required color and high near-infrared reflectivity;

[0024] The first layer is the first metal layer M1, the second layer is the first dielectric layer D, the third layer is the second metal layer M2, the fourth layer is the absorption layer A, and the fifth layer is the low refractive index dielectric layer L;

[0025] If s=1, the sixth layer is a high-refractive-index medium layer H, and the seventh layer is a low-refractive-index medium layer L;

[0026] If s≥2, the sixth layer is a high refractive index medium layer H, and the seventh layer is a low refractive index medium layer L; the structure of the sixth to seventh layers is repeated to set the eighth to last layers;

[0027] Step 3: placing an object with a flat surface as a substrate in a film forming equipment chamber; cleaning and pre-treating the substrate surface in a reaction chamber to remove surface contaminants;

[0028] Step 4, depositing 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;

[0029] Step 5: Separate the substrate from the first layer to obtain the prepared target film.

[0030] Furthermore, in step 3, the method for cleaning the substrate surface is one of ion bombardment or high-temperature baking; in step 4, the method for depositing the first metal layer M1, the first dielectric layer D, the second metal layer M2, the absorption layer A, the low refractive index dielectric layer L and the high refractive index dielectric layer H is one of physical vapor deposition and chemical vapor deposition.

[0031] 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;

[0032] 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.

[0033] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0034] 1. Improved color purity: Add a one-dimensional photonic crystal structure L(HL)^s as the second continuous state, and use the band gap characteristics of the photonic crystal. Through the one-dimensional photonic crystal structure, only light of a specific wavelength can be absorbed, while light of other wavelengths is reflected, thereby reducing overall heat absorption and more effectively regulating the propagation and scattering of light. The interaction of the double continuous states (the first continuous state and the second continuous state) makes the Fano resonance peak in the spectrum sharper, thereby improving color purity. In color science, a sharp resonance peak means that the intensity change of reflected or transmitted light is more significant within a specific wavelength range, which is crucial to achieving high-purity color.

[0035] 2. Improved brightness: The dual continuous state enhances the interaction between light and structure, so the light absorption and scattering efficiency at a specific wavelength is improved. The specific wavelength depends on the situation. For example, to achieve green, the wavelength range of this specific wavelength is 400-500nm and 570-800nm, that is, other visible light wavelength ranges except the green light wavelength range of 500-570nm. The dual continuous state enhances the overall interference effect, which can significantly change the transmission and reflection characteristics of light, thereby affecting the light absorption and scattering efficiency. This enhanced optical response significantly improves the brightness of the structure in reflected or transmitted light.

[0036] 3. Wider spectrum control: The structure of the present invention has a second continuous state, so it has higher flexibility in spectrum control. By adjusting the relative intensity and phase difference between the two continuous states, fine control of specific wavelengths of light can be achieved, which is difficult to achieve in traditional Fano structures. Different materials have different refractive indices and light absorption characteristics.

[0037] 4. Enhanced optical stability: Due to the introduction of the second continuous state, the optical performance of the structure of the present invention is more stable under environmental changes (humidity, temperature, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Figure 1 A schematic diagram of the structure of a structural color film based on Fano resonance to achieve a cooling function provided by the present invention.

[0040] Figure 2 The present invention provides an MDMA structure of a structural color film that realizes a cooling function based on Fano resonance.

[0041] Figure 3 The present invention provides a flowchart of a method for preparing a structural color film that realizes a cooling function based on Fano resonance.

[0042] Figure 4 A structural color thin film deposition flow chart for realizing a cooling function based on Fano resonance provided by the present invention.

[0043] Figure 5 This is a reflection spectrum diagram of a structural color thin film multilayer structure based on Fano resonance to achieve cooling function at vertical incidence in Example 1 provided by the present invention.

[0044] Figure 6 This is a chromaticity coordinate diagram of a structural color thin film multilayer structure based on Fano resonance to achieve a cooling function at vertical incidence in Example 1 provided by the present invention.

[0045] Figure 7 This is a reflection spectrum diagram of a structural color thin film multilayer structure based on Fano resonance to achieve cooling function at vertical incidence in Example 2 provided by the present invention.

[0046] Figure 8 A chromaticity coordinate diagram of a structural color thin film multilayer structure based on Fano resonance to achieve a cooling function at vertical incidence in Example 2 provided by the present invention.

[0047] Fig. 9 This is a reflection spectrum diagram of a structural color thin film multilayer structure based on Fano resonance to achieve cooling function at vertical incidence in Example 3 provided by the present invention.

[0048] Fig.10 This is a chromaticity coordinate diagram of a structural color thin film multilayer structure based on Fano resonance to achieve a cooling function at vertical incidence in Example 3 provided by the present invention.

[0049] Fig.11 This is a reflection spectrum diagram of a structural color thin film multilayer structure based on Fano resonance to achieve cooling function at vertical incidence in Example 4 provided by the present invention.

[0050] Fig.12 This is a chromaticity coordinate diagram of a structural color thin film multilayer structure based on Fano resonance to achieve a cooling function at vertical incidence in Example 4 provided by the present invention.

[0051] Fig.13 This is a reflection spectrum diagram of a structural color thin film multilayer structure based on Fano resonance to achieve cooling function at vertical incidence in Example 5 provided by the present invention.

[0052] Fig.14 This is a chromaticity coordinate diagram of a structural color thin film multilayer structure based on Fano resonance to achieve a cooling function at vertical incidence in Example 5 provided by the present invention.

[0053] Fig.15 This is a reflection spectrum diagram of a structural color thin film multilayer structure based on Fano resonance to achieve cooling function at vertical incidence in Example 6 provided by the present invention.

[0054] Fig.16 This is a chromaticity coordinate diagram of a structural color thin film multilayer structure based on Fano resonance to achieve a cooling function at vertical incidence in Example 6 provided by the present invention. DETAILED DESCRIPTION

[0055] 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.

[0056] The design ideas of the present invention are as follows:

[0057] In Fano resonance, the continuous state and the discrete state are coupled and influence each other. The continuous state provides a smoothly changing spectral background, and the drastic changes in the discrete state reflectivity will always revolve around the continuous state. The construction of discrete state structures can be achieved through single-layer dielectric films and metal-dielectric-metal (M1DM2) structures. The single-layer dielectric film is the simplest membrane structure. There is a refractive index difference or admittance mismatch at the interface between the film and the air, which brings Fresnel reflection. The effect is similar to the parallel plates in the basic structure of the FP cavity, and the gap between the plates is replaced by the film material. If the frequency matches the membrane structure parameters, the electromagnetic wave will be bound when passing through the single-layer film like in the FP cavity, forming a gathering area of ​​strong electric field. Dielectric materials with different refractive indices produce different discrete states. When the incident medium is air, the higher the refractive index of the dielectric material, the better.

[0058] However, the single-layer dielectric film structure has the disadvantage of low interface reflection. Therefore, it is possible to consider adding a metal high-reflection layer on both sides of the single-layer dielectric film to form an M1DM2 structure, using metal materials to increase interface reflection so that electromagnetic waves can form better resonance in the cavity, thereby obtaining a discrete state with lower radiation loss and narrower bandwidth. In order to obtain a high-quality discrete state, the present invention adopts the M1DM2 structure to achieve this.

[0059] When constructing a continuous state, it is necessary to consider maintaining the low reflectivity of the continuous state trough as much as possible and ensuring that it can cover the visible light region. This can be achieved through a metal-absorber (M2A) structure and a dielectric one-dimensional photonic crystal structure. A dielectric one-dimensional photonic crystal structure usually has a wide reflection band. When constructing it, a high and low refractive index repeated periodic structure is mainly used. The reflectivity of the reflection area increases with the increase in the number of periods.

[0060] See also Figure 1 and Figure 2The present invention discloses a structural color film that realizes a cooling function based on Fano resonance. The film includes a structure stacked in sequence from bottom to top: M1DM2AL(HL)^s. The structure of the film is an asymmetric structure, wherein M1 represents the first metal layer, M2 represents the second metal layer, D represents the first dielectric layer, A represents the absorption layer, L represents the low refractive index dielectric layer, and H represents the high refractive index dielectric layer; s represents the number of repeated stacking times, and s is a positive integer; the M1DM2 structure serves as a discrete state, M2A serves as a first continuous state, and L(HL)^s serves as a second continuous state. Since the role of L(HL)^s is to serve as the second continuous state in the Fano structure, in the Fano resonance, the interference between the discrete state and the continuous state is the basis for generating an asymmetric resonance line shape. Adding a second continuous state means adding a new interference path. These additional paths can be superimposed on the original interference paths to enhance the overall interference effect. The interference effect is the result of the superposition of light waves. It can accurately control the phase, amplitude and propagation path of the light waves. Therefore, adding a second continuous state can effectively regulate the propagation and scattering of light and reduce the reflectivity of non-target bands. If only one first dielectric layer D is used, the effect of reducing the reflectivity of non-target bands cannot be achieved well.

[0061] By changing the material of the continuous state, the speed of light propagation and the degree of attenuation in it can be changed, thereby affecting the intensity and phase of the continuous state; changing the thickness of the material in the continuous state will change the optical path of light in it, thereby affecting the phase. An increase in thickness will cause a phase delay, while a decrease in thickness will cause a phase advance: when the thickness increases, the optical path of light propagation also increases. Since the phase is proportional to the optical path, an increase in the optical path will cause an increase in the phase, that is, a phase delay; when the thickness decreases, the optical path of light propagation decreases, which will cause a decrease in the phase, that is, a phase advance.

[0062] Preferably, the material of the first metal layer M1 and the second metal layer M2 is one of Ag (silver), Ti (titanium), Al (aluminum), Au (gold) and Cu (copper).

[0063] Preferably, the material of the first dielectric layer D is MgF2 (magnesium fluoride), SiO2 (silicon dioxide), TiO2 (titanium oxide), AlF3 (aluminum fluoride), CeF3 (cerium fluoride), LaF3 (lanthanum chloride), Na3AlF6 (sodium hexachloroaluminate), NdF3 (neodymium fluoride), BaF2 (barium fluoride), CaF2 (calcium fluoride), LiF (lithium fluoride), Ta2O5 (tantalum oxide), HfO2 (hafnium oxide), ZrO2 (zirconium oxide), Nb2O5 (niobium oxide), La2T One or a mixture of at least two of i2O7 (lanthanum titanate), Y2O3 (yttrium oxide), ZnS (zinc sulfide), Si3N4 (silicon nitride), Bi2O3 (bismuth oxide), CeO2 (cerium oxide), Cr2O3 (chromium oxide), MgO (magnesium oxide), Nd2O3 (neodymium oxide), ZnO (zinc oxide) and Al2O3 (aluminum oxide).

[0064] Preferably, the material of the absorption layer is one of Ni (nickel), Ti (titanium), Cr (chromium), Fe2O3 (iron oxide), Ge (germanium), single crystal silicon, polycrystalline silicon, Sb2S3 (antimony sulfide), Sb2Se3 (antimony selenide), VO2 (vanadium dioxide), Ge2Sb2Te5 (GST), Ge2Sb2Se4Te1 (GSST) and GeTe (GT).

[0065] Preferably, the material of the high refractive index dielectric layer H is one of Ta2O5 (tantalum oxide), TiO2 (titanium oxide), HfO2 (hafnium oxide), ZrO2 (zirconium oxide), Nb2O5 (niobium oxide), La2T i2O7 (lanthanum titanate), Y2O3 (yttrium oxide), ZnS (zinc sulfide), Si3N4 (silicon nitride), Bi2O3 (bismuth oxide), CeO2 (cerium oxide), Cr2O3 (chromium oxide), MgO (magnesium oxide), Nd2O3 (neodymium oxide) and ZnO (zinc oxide);

[0066] The material of the low refractive index medium layer L is one of MgF2 (magnesium fluoride), SiO2 (silicon dioxide), Al2O3 (aluminum oxide), Al F3 (aluminum fluoride), CeF3 (cerium fluoride), LaF3 (lanthanum chloride), Na3Al F6 (sodium hexachloroaluminate), NdF3 (neodymium fluoride), BaF2 (barium fluoride), CaF2 (calcium fluoride) and LiF (lithium fluoride).

[0067] Preferably, the thickness of the first metal layer M1 is above 100 nm to provide high reflectivity;

[0068] The thickness of the second metal layer M2 is in the range of 5-35 nm, and as a coupling layer between the discrete state and the first continuous state, if it is too thin, the reflectivity will be significantly reduced, and if it is too thick, the discrete state and the continuous state will be decoupled, and the Fano resonance will disappear;

[0069] The thickness of the first dielectric layer D is in the range of 5-1000 nm, and thin film structural colors of different colors can be obtained by adjusting the material and thickness of the dielectric layer in the discrete state;

[0070] The thickness of the absorption layer A is in the range of 1-30 nm, and the absorption efficiency of the corresponding band can be changed by adjusting the thickness of the absorption layer;

[0071] The thickness of the low refractive index medium layer L is in the range of 5-1000 nm;

[0072] The thickness of the high refractive index medium layer H is in the range of 5-1000 nm. Fine control of light of a specific wavelength can be achieved by adjusting the thickness and material of the high and low refractive index medium materials.

[0073] Preferably, the number of repeated stacking times s=1 or 2.

[0074] The four layers below this film structure constitute Fano, a commonly used metal-dielectric-metal-absorber (M1DM2A) structure, such as Figure 2 As shown. The M2A structure is used as resonant cavity 1, and the total electric field in the cavity is E1. The M1DM2 structure is used as resonant cavity 2, and the total electric field in the cavity is E2. Let the thickness of the DM2A layer be L d , L m and L a The complex refractive index is n d 、n m and n a , define the intensity ratio (A k ) is the electric field in the kth resonant cavity (E k ) and the electric field injected into the kth resonant cavity The ratio of in:

[0075]

[0076] Among them, r a0 and r am Represents the reflection coefficient of the absorption layer. Resonator phase φ i (ω) by A i (ω)=

[0077] |A i (ω)|exp[iφ i (ω)] definition, when the two resonant cavities are coupled, resonant cavity 1 is incident on the upper layer E iWhen driven by a field, the total field injected into resonant cavity 1 can be expressed as:

[0078]

[0079] The field in resonator 2 is generated by resonator 1 propagating downward through the gap, so the total field injected into resonator 2 is expressed as:

[0080]

[0081] in, and represents the transmission coefficient of the metal spacer layer. The above relationship can be expressed as the matrix equation of E1 and E2:

[0082]

[0083] The coupling between E1 and E2 occurs through the off-diagonal terms in the matrix. The above formula can be used to obtain the reflectivity of the coupled resonator. The reflectivity has a narrow reflection band and presents an asymmetric Fano line shape with a peak at the resonant frequency. When the top is an optically opaque metal film, that is, the cavity is decoupled (L m →∞), the off-diagonal terms vanish and the Fano resonance disappears.

[0084] When achieving high near-infrared reflection, materials with low absorption coefficients in the near-infrared band should be selected first. The absorption coefficient is a parameter that measures the material's ability to absorb light energy. In the near-infrared band, materials with low absorption coefficients can reduce the absorption of light energy, thereby increasing the reflectivity. That is, the material has a weak absorption capacity for near-infrared light and can effectively reflect the light back. Commonly used materials are metal films and dielectric materials. Metal films include silver (Ag), aluminum (Al), gold (Au), copper (Cu), etc., which have high reflectivity and low absorption coefficients. Dielectric materials include SiO2 (silicon dioxide), TiO2 (titanium dioxide), Al2O3 (aluminum oxide), etc.

[0085] Traditional thin film structural color structures (such as interference color films, photonic crystal films, etc.) produce colors through light interference, diffraction or photonic bandgap effects. These structures are widely used in display technology, decorative materials and anti-counterfeiting, but these films tend to accumulate heat under sunlight, causing the surface temperature to rise, which is disadvantageous in some application scenarios.

[0086] The structure of the present invention retains the advantages of traditional thin film structural color and increases the cooling effect. The reflectivity in the near-infrared band reaches more than 85%. Near-infrared light carries a lot of heat. By reflecting near-infrared light, the heat absorbed by the surface of the object can be reduced, thereby reducing the temperature of the surface of the object. The present invention uses metal and dielectric materials with low absorption coefficients in the near-infrared band, and adds a one-dimensional photonic crystal structure as a continuous state. By utilizing the band gap characteristics of the photonic crystal and designing a specific photonic crystal structure, only light of a specific wavelength can be absorbed, while light of other wavelengths is reflected, thereby reducing the overall heat absorption.

[0087] The structure of the present invention can not only provide rich visual effects, but also has a significant cooling function, which makes it have greater advantages in the following application scenarios:

[0088] 1. Outdoor billboards: Under direct sunlight, they can maintain a lower temperature, extend service life and reduce energy consumption.

[0089] 2. Building materials: used on the exterior surface of buildings, they can not only beautify the buildings but also reduce the heat island effect of the buildings.

[0090] 3. Electronic equipment: heat dissipation components used in electronic equipment to improve the heat dissipation efficiency of the equipment and ensure stable operation of the equipment.

[0091] In this specific embodiment, the preparation of the thin film can be achieved by physical vapor deposition (PVD) or chemical vapor deposition (CVD) methods, wherein the physical vapor deposition method includes a combination of different technologies such as ion beam sputtering deposition (IBS), magnetron sputtering deposition (MS), electron beam evaporation (EB) or electron beam evaporation ion assisted deposition (EBD-IAD).

[0092] The present invention also provides a method for preparing a structural color film that realizes a cooling function based on Fano resonance. The method needs to provide a structural color film that realizes a cooling function based on Fano resonance as described above, and specifically comprises the following steps:

[0093] Step 1, the film to be plated is an asymmetric structure, and its structure is: M1DM2AL(HL)^s, the structure of the film is an asymmetric structure, wherein M1 represents the first metal layer, M2 represents the second metal layer, D represents the first dielectric layer, A represents the absorption layer, L represents the low refractive index dielectric layer, and H represents the high refractive index dielectric layer; s represents the number of repeated stacking, and s is a positive integer; the M1DM2 structure is used as a discrete state, M2A is used as a first continuous state, and L(HL)^s is used as a second continuous state;

[0094] Step 2, according to the user's functional requirements, 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; by adjusting the thickness and material of each layer in the film structure, the film can present the desired color and high near-infrared reflectivity; when adjusting the material used in the film structure, select materials with low absorption coefficients in the near-infrared band to achieve high near-infrared reflectivity; when adjusting the thickness, because the Fano structure forms a resonance peak through the coupling of discrete and continuous states, the discrete state determines the position of the resonance peak, so if you want to adjust the thickness to achieve the desired color, you only need to adjust the thickness of D in the discrete state M1DM2 structure, and the thickness of the continuous state will also change accordingly, which can better reduce the reflectivity of non-target bands and improve color indicators.

[0095] The first layer is the first metal layer M1, the second layer is the first dielectric layer D, the third layer is the second metal layer M2, the fourth layer is the absorption layer A, and the fifth layer is the low refractive index dielectric layer L;

[0096] If s=1, the sixth layer is a high-refractive-index medium layer H, and the seventh layer is a low-refractive-index medium layer L;

[0097] If s≥2, the sixth layer is a high refractive index medium layer H, and the seventh layer is a low refractive index medium layer L; the structure of the sixth to seventh layers is repeated to set the eighth to last layers;

[0098] Step 3, placing a flat surface object as a substrate SUB in a film forming equipment cavity; cleaning and pre-treating the surface of the substrate SUB in a reaction chamber to remove surface pollutants; the material of the substrate SUB is polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate (PET), cellulose triacetate (TAC), polymethyl methacrylate (PMMA), polycarbonate / polymethyl methacrylate composite material (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 polyvinylidene fluoride (PVDF); the method for cleaning the surface of the substrate SUB is one of ion bombardment or high temperature baking;

[0099] Step 4, depositing a first layer on the upper surface of the substrate SUB, and after the first layer is completely deposited, depositing a second layer on the upper surface of the first layer, and after the second layer is completely deposited, depositing the next layer on the upper surface of the second layer, and depositing them in sequence until the last layer is deposited to complete the coating; the method of depositing the first metal layer M1, the first dielectric layer D, the second metal layer M2, the absorption layer A, the low refractive index dielectric layer L and the high refractive index dielectric layer H in step 4 adopts one of physical vapor deposition and chemical vapor deposition.

[0100] Step 5: Separate the substrate SUB from the first layer to obtain the prepared target film. The substrate SUB has a release layer material on its upper surface, 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.

[0101] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions in the implementation modes of the present invention are clearly and completely described below in combination with the accompanying drawings and embodiments.

[0102] Example 1

[0103] This embodiment provides a structural color film that realizes a cooling function based on Fano resonance. The structural color device is composed of a substrate SUB, a first metal layer M1 (Ag), a first dielectric layer D (MgF2), a second metal layer M2 (Ag), an absorption layer A (GSST), and a low refractive index dielectric layer L (SiO2) and a high refractive index dielectric layer H (TiO2) that construct a one-dimensional photonic crystal structure. The one-dimensional photonic crystal structure of this embodiment adopts a three-layer structure, and the specific thickness of each layer is given in Table 1. Figure 5 is the reflection spectrum of Example 1 at vertical incidence, Figure 6 is the chromaticity coordinate diagram of Example 1 at a vertical incident angle. Figure 5 It can be seen from the reflectivity spectrum that compared with the traditional Fano structure, the addition of the additional continuous state obviously makes the Fano resonance peak in the spectrum sharper, and the reflectivity of the non-target band is also significantly reduced, which shows that the structural design can obtain high saturation and high purity colors. The average reflectivity in the wavelength range of 800-2000nm is calculated to be 96.686%, the red brightness value L'=34.7, and the chromaticity coordinates of red are (0.6399, 0.3300). The red color of this design is very close to the standard red chromaticity coordinates (0.6400, 0.3300) used in liquid crystal display. This embodiment not only achieves a better red effect, but also achieves high reflection in the near-infrared band, achieving a cooling effect.

[0104] Table 1

[0105] Material Ag <![CDATA[MgF2]]> Ag GSST <![CDATA[SiO2]]> <![CDATA[TiO2]]> <![CDATA[SiO2]]> Physical thickness (nm) 100 184.43 30.13 15.26 149.17 187.12 76.80

[0106] Example 2

[0107] This embodiment provides a structural color film that realizes a cooling function based on Fano resonance. The structural color device is composed of a substrate SUB, a first metal layer M1 (Ag), a first dielectric layer D (Ta2O5), a second metal layer M2 (Ag), an absorption layer A (GSST), and a low refractive index dielectric layer L (SiO2) and a high refractive index dielectric layer H (TiO2) that construct a one-dimensional photonic crystal structure. The one-dimensional photonic crystal structure of this embodiment adopts a five-layer structure, and the specific thickness of each layer is given in Table 2. Figure 7 is the reflection spectrum of Example 2 at vertical incidence, Figure 8 The chromaticity coordinate diagram of Example 2 at a vertical incident angle. The average reflectivity in the wavelength range of 800-2000nm is calculated to be 96.358%, the green brightness value L'=72.9, and the green chromaticity coordinates are (0.3002, 0.5998). The green color of this design is very close to the standard green chromaticity coordinates (0.3000, 0.6000) used in liquid crystal display. This embodiment not only achieves a better green effect, but also achieves high reflection in the near-infrared band, achieving a cooling effect.

[0108] Table 2

[0109]

[0110] Example 3

[0111] This embodiment provides a structural color film that realizes a cooling function based on Fano resonance. The structural color device is composed of a substrate Sub, a first metal layer M1 (Ag), a first dielectric layer D (Al2O3), a second metal layer M2 (Ag), an absorption layer A (GSST), and a low refractive index dielectric layer L (SiO2) and a high refractive index dielectric material H (TiO2) that construct a one-dimensional photonic crystal structure. The one-dimensional photonic crystal structure of this embodiment adopts a three-layer structure, and the specific thickness of each layer is given in Table 3. Fig. 9 is the reflection spectrum of Example 3 at vertical incidence, Fig.10 The chromaticity coordinate diagram of Example 3 at a vertical incident angle. The average reflectivity in the wavelength range of 800-2000nm is calculated to be 96.602%, and the blue brightness value L'=27.7. The chromaticity coordinates of blue are (0.1725, 0.0621), and the blue color of this design is very close to the standard blue chromaticity coordinates (0.1500, 0.0600) used in liquid crystal display. This embodiment not only achieves a better blue effect, but also achieves high reflection in the near-infrared band, achieving a cooling effect.

[0112] Table 3

[0113] Material Ag <![CDATA[Al2O3]]> Ag GSST <![CDATA[SiO2]]> <![CDATA[TiO2]]> <![CDATA[SiO2]]> Physical thickness (nm) 100 105 24.21 15.96 41 121.10 54.13

[0114] Example 4

[0115] This embodiment provides a structural color film that realizes a cooling function based on Fano resonance. The structural color device is composed of a substrate SUB, a first metal layer M1 (Ag), a first dielectric layer D (Ta2O5), a second metal layer M2 (Ag), an absorption layer A (GST), and a low refractive index dielectric layer L (SiO2) and a high refractive index dielectric layer H (TiO2) that construct a one-dimensional photonic crystal structure. The one-dimensional photonic crystal structure of this embodiment adopts a three-layer structure, and the specific thickness of each layer is given in Table 4. Fig.11 is the reflection spectrum of Example 4 at vertical incidence, Fig.12 This is the chromaticity coordinate diagram of Example 4 at a vertical incident angle. The average reflectivity in the wavelength range of 800-2000nm is calculated to be 86.863%, the three stimulus values ​​of cyan are (47.0886, 69.2878, 95.6001), the converted RGB values ​​are (52, 241, 243), the chromaticity coordinates of cyan are (0.2221, 0.3269), and the cyan brightness value L'=86.6. This embodiment not only achieves a better cyan effect, but also achieves high reflection in the near-infrared band, achieving a cooling effect.

[0116] Table 4

[0117] Material Ag <![CDATA[Ta2O5]]> Ag GST <![CDATA[SiO2]]> <![CDATA[TiO2]]> <![CDATA[SiO2]]> Physical thickness (nm) 100 83.28 15 5 76.18 50.56 10

[0118] Example 5

[0119] This embodiment provides a structural color film that realizes a cooling function based on Fano resonance. The structural color device is composed of a substrate SUB, a first metal layer M1 (Ag), a first dielectric layer D (Ta2O5), a second metal layer M2 (Al), an absorption layer A (GST), and a low refractive index dielectric layer L (SiO2) and a high refractive index dielectric layer H (TiO2) that construct a one-dimensional photonic crystal structure. The one-dimensional photonic crystal structure of this embodiment adopts a three-layer structure, and the specific thickness of each layer is given in Table 5. Fig.13 is the reflection spectrum of Example 5 at vertical incidence, Fig.14 This is the chromaticity coordinate diagram of Example 5 at a vertical incident angle. The average reflectivity in the wavelength range of 800-2000nm is calculated to be 85.526%, the three stimulus values ​​of magenta are (48.4559, 27.5331, 81.1829), the converted RGB values ​​are (224, 80, 235), the chromaticity coordinates of magenta are (0.3083, 0.1752), and the magenta brightness value L'=59.5. This embodiment not only achieves a good magenta effect, but also achieves high reflection in the near-infrared band, achieving a cooling effect.

[0120] Table 5

[0121] Material Ag <![CDATA[Ta2O5]]> Al GST <![CDATA[SiO2]]> <![CDATA[TiO2]]> <![CDATA[SiO2]]> Physical thickness (nm) 100 80 17.67 5 147 65 30

[0122] Example 6

[0123] This embodiment provides a structural color film that realizes a cooling function based on Fano resonance. The structural color device is composed of a substrate SUB, a first metal layer M1 (Ag), a first dielectric layer D (La2Ti2O7), a second metal layer M2 (Al), an absorption layer A (Sb2S3), and a low refractive index dielectric layer L (SiO2) and a high refractive index dielectric layer H (TiO2) that construct a one-dimensional photonic crystal structure. The one-dimensional photonic crystal structure of this embodiment adopts a five-layer structure, and the specific thickness of each layer is given in Table 6. Fig.15 is the reflection spectrum of Example 6 at vertical incidence, Fig.16 This is the chromaticity coordinate diagram of Example 6 at a vertical incident angle. The average reflectivity in the wavelength range of 800-2000nm is calculated to be 93.23%, the tristimulus values ​​of yellow are (69.1297, 80.4566, 7.8377), the converted RGB values ​​are (251, 236, 141), the chromaticity coordinates of yellow are (0.4391, 0.5111), and the yellow brightness value L'=91.9. This embodiment not only achieves a better yellow effect, but also achieves high reflection in the near-infrared band, achieving a cooling effect.

[0124] Table 6

[0125]

[0126] 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 structural color film for realizing cooling function based on Fano resonance, characterized in that: The film includes a structure stacked in sequence from bottom to top: M1DM2AL(HL)^s. The structure of the film is an asymmetric structure, wherein M1 represents the first metal layer, M2 represents the second metal layer, D represents the first dielectric layer, A represents the absorption layer, L represents the low refractive index dielectric layer, and H represents the high refractive index dielectric layer; s represents the number of repeated stacking, and s is a positive integer; the M1DM2 structure is a discrete state, M2A is a first continuous state, and L(HL)^s is a second continuous state.

2. The structural color film for realizing cooling function based on Fano resonance according to claim 1, characterized in that: The material of the first metal layer M1 and the second metal layer M2 is one of Ag, Ti, Al, Au and Cu.

3. The structural color film for realizing cooling function based on Fano resonance according to claim 1, characterized in that: The material of the first dielectric layer D is one or a mixture of at least two of MgF2, SiO2, TiO2, AlF3, CeF3, LaF3, Na3AlF6, NdF3, BaF2, CaF2, LiF, Ta2O5, HfO2, ZrO2, Nb2O5, La2Ti2O7, Y2O3, ZnS, Si3N4, Bi2O3, CeO2, Cr2O3, MgO, Nd2O3, ZnO and Al2O3.

4. The structural color film for realizing cooling function based on Fano resonance according to claim 1, characterized in that: The material of the absorption layer is one of Ni, Ti, Cr, Fe2O3, Ge, single crystal silicon, polycrystalline silicon, Sb2S3, Sb2Se3, VO2, Ge2Sb2Te5, Ge2Sb2Se4Te1 and GeTe.

5. The structural color film for realizing cooling function based on Fano resonance according to claim 1, characterized in that: The material of the high refractive index medium layer H is one of Ta2O5, TiO2, HfO2, ZrO2, Nb2O5, La2Ti2O7, Y2O3, ZnS, Si3N4, Bi2O3, CeO2, Cr2O3, MgO, Nd2O3 and ZnO; the material of the low refractive index medium layer L is one of MgF2, SiO2, Al2O3, AlF3, CeF3, LaF3, Na3AlF6, NdF3, BaF2, CaF2 and LiF.

6. The structural color film for realizing cooling function based on Fano resonance according to claim 1, characterized in that: The thickness of the first metal layer M1 is above 100 nm; The thickness of the second metal layer M2 is in the range of 5-35 nm; The thickness of the first dielectric layer D is in the range of 5-1000 nm; The thickness of the absorption layer A ranges from 1 to 30 nm; The thickness of the low refractive index medium layer L is in the range of 5-1000 nm; The thickness of the high refractive index medium layer H is in the range of 5-1000 nm.

7. The structural color film for realizing cooling function based on Fano resonance according to claim 1, characterized in that: The number of repeated stacking is s=1 or 2.

8. A method for preparing a structural color film based on Fano resonance to achieve a cooling function, characterized in that: The method needs to provide a structural color film based on Fano resonance to achieve a cooling function as described in any one of claims 1 to 7, and specifically comprises the following steps: Step 1, the film to be plated is an asymmetric structure, and its structure is: M1DM2AL(HL)^s, the structure of the film is an asymmetric structure, wherein M1 represents the first metal layer, M2 represents the second metal layer, D represents the first dielectric layer, A represents the absorption layer, L represents the low refractive index dielectric layer, and H represents the high refractive index dielectric layer; s represents the number of repeated stacking, and s is a positive integer; the M1DM2 structure is used as a discrete state, M2A is used as a first continuous state, and L(HL)^s is used as a second continuous state; Step 2: according to the functional requirements of the user, 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 are set, so that the film presents the required color and high near-infrared reflectivity; The first layer is the first metal layer M1, the second layer is the first dielectric layer D, the third layer is the second metal layer M2, the fourth layer is the absorption layer A, and the fifth layer is the low refractive index dielectric layer L; If s=1, the sixth layer is a high-refractive-index medium layer H, and the seventh layer is a low-refractive-index medium layer L; If s≥2, the sixth layer is a high refractive index medium layer H, and the seventh layer is a low refractive index medium layer L; the structure of the sixth to seventh layers is repeated to set the eighth to last layers; Step 3: placing an object with a flat surface as a substrate in a film forming equipment chamber; cleaning and pre-treating the substrate surface in a reaction chamber to remove surface contaminants; Step 4, depositing 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.

9. The method for preparing a structural color film based on Fano resonance to achieve a cooling function as claimed in claim 8, characterized in that: In step 3, the method for cleaning the substrate surface is one of ion bombardment or high-temperature baking; in step 4, the method for depositing the first metal layer M1, the first dielectric layer D, the second metal layer M2, the absorption layer A, the low refractive index dielectric layer L and the high refractive index dielectric layer H is one of physical vapor deposition and chemical vapor deposition.

10. The method for preparing a structural color film for realizing a cooling function based on Fano resonance according to claim 8, 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.

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