Structural color film with cooling function based on fano resonance and preparation method thereof

Abstract

The application discloses a structural color film achieving a cooling function based on Fano resonance, and the film comprises a structure which is sequentially and layerwisely arranged from bottom to top as M1DM2AL(HL)^s, and the film is of 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 a repeating stacking number, and s is a positive integer; the M1DM2 structure serves as a discrete state, the M2A serves as a first continuous state, and the L(HL)^s serves as a second continuous state. The application further discloses a preparation method of the structural color film achieving the cooling function based on the Fano resonance, and the structural color film with high brightness, high purity and a wide color gamut is achieved, and meanwhile, near-infrared reflection is ensured.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to a structural color thin film with cooling function based on Fano resonance and its preparation method. Background Technology

[0002] Structural color is a color phenomenon originating from the microscopic structure of an object. It utilizes the physical effects of interference, diffraction, and scattering of light at different frequencies through this microstructure, resulting in a specific spectral power distribution of the light ultimately reaching the human eye. Compared to traditional coloring methods such as organic dyes and chemical pigments, structural color offers significant advantages in purity, brightness, resolution, lifespan, and environmental safety, thus holding significant application value in optical imaging / display / detection devices, anti-counterfeiting, automotive films, colored decorations, and optical filters. To date, researchers have discussed various resonance mechanisms for generating structural color, such as guided-mode resonance (GMR), plasmon resonance (SPR), and Mie resonance. However, the fabrication of these structural colors often involves complex nanoscale patterns, which presents drawbacks such as high cost, complex processes, and long processing times for large-scale and large-area applications. In contrast, planar thin-film structural color generation based on photolithography-free methods offers a simple color generation solution, which is currently the preferred approach for realizing structural color in industrial applications.

[0003] In recent years, researchers in the field of color have proposed many excellent design and fabrication schemes, including (HL). n Examples of structural color designs include high- and low-refractive-index repetitive periodic structures, asymmetric Fabry-Perot (FP) cavities, and structures employing single or composite absorber layers. For instance, patent CN116540331A designs a thin-film structural color structure using stacked high- and low-refractive-index materials, employing all-dielectric materials for reflective structural color design. The number of film layers and the ratio of high to 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, achieving different saturations of red by finely adjusting the film layer thickness while maintaining the structure and materials.

[0004] However, researching layered thin-film structures that simultaneously possess high brightness, high purity, and a wide color gamut remains a challenging task. In 1865, Fano Hugo proposed the concept of Fano resonance to explain the quantum interference phenomenon between electrons in rare gas atoms. Unlike the Lorentz linearity formed by traditional resonant cavity structures, the linearity produced by Fano resonance exhibits antisymmetric or asymmetric characteristics, capable of simultaneously forming a peak and a valley within a shorter frequency range, resulting in a narrower spectral bandwidth. In color science, this translates to better saturation.

[0005] Heat transfer occurs in three forms: radiation, convection, and conduction. The sun's heat transfer to Earth is radiation; objects heated by radiation then undergo convection and conduction. Sunlight consists of 5% ultraviolet radiation (100nm-400nm), 51% infrared radiation (700nm-2400nm), and 44% visible light (380nm-800nm). Of the solar energy reaching the Earth's surface, over 50% is brought by infrared light. Although infrared light is invisible, it is a major source of heat. Therefore, cooling can be achieved through near-infrared high reflectivity.

[0006] Currently, few studies in the research and development of cooling films combine structural color technology with it. For example, patent CN109291776A designs a car cooling film that absorbs heat from the vehicle interior during phase change using a phase change material, thereby reducing the interior temperature. Patent CN115710780A designs a sunshade cooling film through electrospinning, achieving an average light reflectivity of over 80% in the wavelength range of 300nm to 2500nm. While these films achieve cooling effects, their applications have certain limitations. Therefore, a film structure that simultaneously possesses high brightness, high purity, wide color gamut structural color, and high reflectivity in the near-infrared region has become a crucial issue that urgently needs to be addressed. To achieve both structural color and cooling effects, it is necessary to employ new design and optimization methods to design high-brightness, high-purity, wide color gamut structural color films with cooling capabilities. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a structural color thin film with cooling function based on Fano resonance. The design of the structural color thin film with high near-infrared reflectivity is achieved by using Fano structure and optimizing it according to the chromaticity coordinates of the color standard. While achieving high brightness, high purity and wide color gamut structural color, it ensures high near-infrared reflectivity.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows:

[0009] This invention provides a structured color thin film with cooling function based on Fano resonance. The thin film includes a structure M1DM2AL(HL)^s stacked from bottom to top. The structure of the thin film is asymmetric, 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 times the layers are stacked, 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.

[0010] Furthermore, the first metal layer M1 and the second metal layer M2 are made of 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 the following: 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.

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

[0013] Furthermore, the material of the high refractive index dielectric 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 dielectric layer L is one of MgF2, SiO2, Al2O3, AlF3, CeF3, LaF3, Na3AlF6, NdF3, BaF2, CaF2, and LiF.

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

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

[0016] The thickness of the first dielectric layer D is between 5 and 1000 nm.

[0017] The thickness of the absorption layer A is between 1 and 30 nm;

[0018] The thickness of the low refractive index dielectric layer L ranges from 5 to 1000 nm;

[0019] The thickness of the high refractive index dielectric layer H ranges from 5 to 1000 nm.

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

[0021] This invention also provides a method for preparing a structural color thin film with cooling function based on Fano resonance. This method requires providing a structural color thin film with cooling function based on Fano resonance as described above, and specifically includes the following steps:

[0022] Step 1: The thin film to be deposited has an asymmetric structure, which is: M1DM2AL(HL)^s. The structure of this thin film is asymmetric, where 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.

[0023] Step 2: Set the total number of layers, the material used in each layer, the thickness of each layer, and the distribution between each layer according to the user's functional requirements, so that the film can present 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, then 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, then the sixth layer is a high refractive index medium layer H, and the seventh layer is a low refractive index medium layer L; repeat the structure of the sixth to seventh layers to set the eighth to the last layer;

[0027] Step 3: Place a flat object as a substrate into the cavity of the film forming equipment; perform a pre-cleaning treatment on the substrate surface in the reaction chamber to remove surface contaminants;

[0028] Step 4: Deposit the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating.

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

[0030] Furthermore, the method for cleaning the substrate surface in step 3 is either ion bombardment or high-temperature baking; 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 in step 4 is either physical vapor deposition or chemical vapor deposition.

[0031] Furthermore, the substrate material may be polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate, cellulose triacetate, polymethyl methacrylate, polycarbonate / polymethyl methacrylate composite material, polyimide, polypropylene, polyvinyl chloride, polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane elastomer, polytetrafluoroethylene, fluoroethyl propylene, or polydifluoroethylene.

[0032] The substrate has a release layer material on its upper surface, which separates the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

[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: Adding a one-dimensional photonic crystal structure L(HL)^s as a second continuous state utilizes the bandgap characteristics of photonic crystals. This one-dimensional structure allows only specific wavelengths of light to be absorbed, while other wavelengths are reflected, thus reducing overall heat absorption and more effectively controlling light propagation and scattering. The interaction between the two continuous states (the first and second continuous states) makes the Fano resonance peak in the spectrum sharper, thereby improving color purity. In color science, a sharp resonance peak signifies a more significant change in the intensity of reflected or transmitted light within a specific wavelength range, which is crucial for achieving high-purity colors.

[0035] 2. Enhanced Brightness: The dual continuum enhances the interaction between light and the structure, thus improving light absorption and scattering efficiency at specific wavelengths. These specific wavelengths depend on the specific requirements; for example, to achieve green light, the specific wavelength range is 400-500nm and 570-800nm, encompassing all visible light wavelengths except for the green light range of 500-570nm. The dual continuum enhances the overall interference effect, which can significantly alter the transmission and reflection characteristics of light, thereby affecting light absorption and scattering efficiency. This enhanced optical response significantly improves the brightness of the structure in reflected or transmitted light.

[0036] 3. Wider Spectral Control: The structure of this invention, due to the addition of a second continuous state, offers greater flexibility in spectral control. By adjusting the relative intensity and phase difference between the two continuous states, precise control of specific wavelengths of light can be achieved, which is difficult to realize 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.). Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a structured color thin film that achieves cooling function based on Fano resonance, as provided by the present invention.

[0040] Figure 2 This invention provides an MDMA structure for a structural color thin film that achieves cooling function based on Fano resonance.

[0041] Figure 3 The flowchart illustrates the preparation method of a structural color thin film with cooling function based on Fano resonance, as provided by this invention.

[0042] Figure 4 This invention provides a flow chart for the deposition of structural color thin films based on Fano resonance to achieve cooling function.

[0043] Figure 5 The reflection spectrum of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 1 of the present invention under vertical incidence.

[0044] Figure 6 Chromaticity coordinates of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 1 of the present invention under vertical incidence.

[0045] Figure 7 The reflection spectrum of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 2 of the present invention under vertical incidence.

[0046] Figure 8 Chromaticity coordinates of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 2 of the present invention under vertical incidence.

[0047] Figure 9 The reflection spectrum of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 3 of the present invention under vertical incidence.

[0048] Figure 10 Chromaticity coordinates of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 3 of the present invention under vertical incidence.

[0049] Figure 11 The reflection spectrum of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 4 of the present invention under vertical incidence.

[0050] Figure 12 Chromaticity coordinates of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 4 of the present invention under vertical incidence.

[0051] Figure 13 The reflection spectrum of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 5 of the present invention under vertical incidence.

[0052] Figure 14 Chromaticity coordinates of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 5 of the present invention under vertical incidence.

[0053] Figure 15 The reflection spectrum of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 6 of the present invention under vertical incidence.

[0054] Figure 16 Chromaticity coordinates of a multilayer structured color thin film with cooling function based on Fano resonance in Embodiment 6 of the present invention under vertical incidence. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The design concept of this invention is as follows:

[0057] In Fano resonance, the continuous and discrete states are coupled and influence each other. The continuous state provides a gently changing spectral background, while the drastic changes in reflectivity of the discrete state always revolve around the continuous state. The discrete state structure can be constructed using a single-layer dielectric film and a metal-dielectric-metal (M1DM2) structure. The single-layer dielectric film is the simplest film structure. The interface between the film and air has a refractive index difference or admittance mismatch, resulting in Fresnel reflection, similar to the parallel plates in the basic structure of a Fano cavity, with the gaps between the plates replaced by the thin film material. If the frequency matches the film structure parameters, electromagnetic waves passing through the single-layer film will be confined as in a Fano cavity, forming a region of concentrated strong electric fields. Different refractive indices of the dielectric material produce different discrete states; when the incident medium is air, generally, the higher the refractive index of the dielectric material, the better.

[0058] However, single-layer dielectric film structures suffer from low interfacial reflection. Therefore, it is advisable to add high-reflectivity metal layers to both sides of the single-layer dielectric film to form an M1DM2 structure. The metal material increases interfacial reflection, allowing electromagnetic waves to resonate better within the cavity, resulting in lower radiation loss and a narrower bandwidth discrete state. To achieve high-quality discrete states, this invention employs an M1DM2 structure.

[0059] When constructing a continuous state, it is necessary to consider maintaining the low reflectivity of the continuous state trough as much as possible while ensuring that it can cover the visible light region. This can be achieved through metal-absorbing (M2A) structures and dielectric one-dimensional photonic crystal structures. Dielectric one-dimensional photonic crystal structures typically have a wide reflection band. In their construction, high and low refractive index repeating periodic structures are mainly used, and the reflectivity of the reflection region increases with the increase of the number of periods.

[0060] Please see Figure 1 and Figure 2This invention discloses a structured color thin film that achieves cooling functionality based on Fano resonance. The film comprises a structure M1DM2AL(HL)^s stacked sequentially from bottom to top. This film has an asymmetric structure, where M1 represents a first metal layer, M2 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 stacking repetitions, and s is a positive integer. The M1DM2 structure serves as a discrete state, M2A as a first continuous state, and L(HL)^s as a second continuous state. Since L(HL)^s acts as the second continuous state in the Fano structure, interference between the discrete and continuous states in Fano resonance is the basis for generating the 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, thereby enhancing the overall interference effect. The interference effect is the result of the superposition of light waves. It can precisely control the phase, amplitude and propagation path of light waves. Therefore, adding a second continuous state can effectively regulate the propagation and scattering of light and reduce the reflectivity of non-target wavebands. Using only one first dielectric layer D cannot effectively reduce the reflectivity of non-target wavebands.

[0061] By altering the material within a continuous state, the propagation speed and attenuation of light can be changed, thus affecting the intensity and phase of the continuous state. Changing the thickness of the material within the continuous state alters the optical path length of light, thereby affecting the phase. Increased thickness leads to phase delay, while decreased thickness leads to phase advance: as thickness increases, the optical path length also increases. Since phase is proportional to optical path length, an increase in optical path length leads to an increase in phase, i.e., phase delay; conversely, a decrease in thickness reduces the optical path length, which leads to a decrease in phase, i.e., phase advance.

[0062] Preferably, the first metal layer M1 and the second metal layer M2 are made of 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 (zirconia), Nb2O5 (niobium oxide), or La2T A mixture of one or more of the following: 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 absorber layer is one of Ni (nickel), Ti (titanium), Cr (chromium), Fe2O3 (iron oxide), Ge (germanium), monocrystalline 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 (zirconia oxide), Nb2O5 (niobium oxide), La2Ti2O7 (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 dielectric layer L is one of MgF2 (magnesium fluoride), SiO2 (silicon dioxide), Al2O3 (aluminum oxide), AlF3 (aluminum fluoride), CeF3 (cerium fluoride), LaF3 (lanthanum chloride), Na3AlF6 (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 greater than 100 nm to provide high reflectivity;

[0068] The thickness of the second metal layer M2 is between 5-35nm. 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 ranges from 5 to 1000 nm. Different colors of thin film structure color 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 ranges from 1 to 30 nm, and the absorption efficiency of the corresponding wavelength band can be changed by adjusting the thickness of the absorption layer.

[0071] The thickness of the low refractive index dielectric layer L ranges from 5 to 1000 nm;

[0072] The thickness of the high refractive index medium layer H ranges from 5 to 1000 nm; by adjusting the thickness and material of the high and low refractive index medium materials, precise control of light at a specific wavelength can be achieved.

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

[0074] The four layers beneath this thin film structure constitute Fano, which commonly uses a metal-dielectric-metal-absorbing (M1DM2A) structure, such as... Figure 2 As shown. The M2A structure is used as resonant cavity 1, with a total electric field E1 inside. The M1DM2 structure is used as resonant cavity 2, with a total electric field E2 inside. Let the thickness of the DM2A layer be L. d L m and L a The complex refractive indices are n d n m and n a Define the strength ratio (A) k ) is the electric field (E) inside the k-th resonant cavity. k ) and the electric field injected into the k-th resonant cavity The ratio, that is in:

[0075]

[0076] Where, r a0 and r am This represents the reflection coefficient of the absorption layer. The resonator phase φ i (ω) by A i (ω)=

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

[0078]

[0079] The field in resonator 2 exists because it propagates downwards from resonator 1 through the gap. Therefore, the total field injected into resonant cavity 2 can be expressed as:

[0080]

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

[0082]

[0083] The coupling between E1 and E2 occurs through the off-diagonal terms in the matrix. The reflectivity of the coupled resonator can be obtained from the above equation. The reflectivity exhibits a narrow reflection band, displaying an asymmetric Fano line shape, with a peak at the resonant frequency. When the top is an optically opaque metal film, i.e., cavity decoupling (L... m →∞), off-diagonal terms disappear, and Fano resonance disappears.

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

[0085] Traditional thin-film color structures (such as interference-type color thin films and photonic crystal thin films) generate color through light interference, diffraction, or photonic bandgap effects. These structures have wide applications in display technology, decorative materials, and anti-counterfeiting. However, under sunlight, these thin films often accumulate heat, leading to an increase in surface temperature, which is detrimental in certain applications.

[0086] This invention retains the advantages of traditional thin-film structures while enhancing cooling performance, achieving a reflectivity of over 85% in the near-infrared band. Near-infrared light carries a significant amount of heat; reflecting it reduces heat absorption by the object's surface, thus lowering its temperature. This invention utilizes metal and dielectric materials with low absorption coefficients in the near-infrared band and incorporates a one-dimensional photonic crystal structure as a continuous state. By leveraging the bandgap characteristics of the photonic crystal and designing a specific structure, only light of specific wavelengths is absorbed, while other wavelengths are reflected, thereby reducing overall heat absorption.

[0087] The structure of this invention not only provides rich visual effects but also has a significant cooling function, which makes it more advantageous in the following application scenarios:

[0088] 1. Outdoor billboards: They can maintain a lower temperature under direct sunlight, extending their service life and reducing energy consumption.

[0089] 2. Building materials: Used on the exterior surface of buildings, they can both beautify the buildings and 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 and ensure stable operation of the equipment.

[0091] In this specific embodiment, the thin film can be prepared 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] This invention also provides a method for preparing a structural color thin film with cooling function based on Fano resonance. This method requires providing a structural color thin film with cooling function based on Fano resonance as described above, and specifically includes the following steps:

[0093] Step 1: The thin film to be deposited has an asymmetric structure, which is: M1DM2AL(HL)^s. The structure of this thin film is asymmetric, where 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.

[0094] Step 2: Set the total number of layers, the material used in each layer, the thickness of each layer, and the distribution between layers according to the user's functional requirements. By adjusting the thickness and material of each layer in the thin film structure, the film can present the desired color and high near-infrared reflectivity. When adjusting the material used in the thin film structure, materials with low absorption coefficients in the near-infrared band are selected to achieve high near-infrared reflectivity. When adjusting the thickness, since the Fano structure forms resonance peaks through the coupling of discrete and continuous states, and the discrete state determines the position of the resonance peak, to adjust the thickness to achieve the desired color, the thickness of D in the discrete state M1DM2 structure can be adjusted, and the thickness of the continuous state is also changed accordingly. This can better reduce the reflectivity of non-target bands and improve the color performance.

[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, then 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, then the sixth layer is a high refractive index medium layer H, and the seventh layer is a low refractive index medium layer L; repeat the structure of the sixth to seventh layers to set the eighth to the last layer;

[0098] Step 3: Place a flat object as the substrate SUB in the cavity of the film-forming equipment; perform a pre-cleaning treatment on the surface of the substrate SUB in the reaction chamber to remove surface contaminants; 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 (PC / PMMA), polyimide (PI), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), polyurethane elastomer (TPU), polytetrafluoroethylene (PTFE), fluoroethyl propylene (FEP), or polyvinyl difluoroethylene (PVDF); the cleaning method for the surface of the substrate SUB is either ion bombardment or high-temperature baking;

[0099] Step 4: Deposit the first layer on the upper surface of the substrate SUB. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating. 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 in step 4 is 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 upper surface of the substrate SUB has a release layer material, which is used to separate the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

[0101] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings and examples.

[0102] Example 1

[0103] This embodiment provides a structured color thin film that achieves cooling function based on Fano resonance. The structured color device consists 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) to construct a one-dimensional photonic crystal structure. In this embodiment, the one-dimensional photonic crystal structure adopts a three-layer structure, and the specific thickness of each layer is given in Table 1. Figure 5 This is the reflectance spectrum of Example 1 under vertical incidence. Figure 6 This is a chromaticity coordinate diagram of Example 1 at a vertical incident angle. From... Figure 5 The reflectance spectrum shows that, compared to the traditional Fano structure, the addition of extra continuous states significantly makes the Fano resonance peak in the spectrum sharper, and the reflectance in non-target wavelengths is also significantly reduced. This indicates that this structural design can achieve high saturation and high purity colors. Calculations show an average reflectance of 96.686% in the 800-2000nm wavelength range, a red luminance value L' = 34.7, and red chromaticity coordinates of (0.6399, 0.3300). The red color in this design is very close to the standard red chromaticity coordinates (0.6400, 0.3300) used in liquid crystal displays. This embodiment achieves good red color performance while also achieving high reflectance in the near-infrared band, resulting in 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 structured color thin film that achieves cooling function based on Fano resonance. The structured color device consists 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) to construct a one-dimensional photonic crystal structure. In this embodiment, the one-dimensional photonic crystal structure adopts a five-layer structure, and the specific thickness of each layer is given in Table 2. Figure 7 This is the reflection spectrum of Example 2 under vertical incidence. Figure 8 This is the chromaticity coordinate diagram of Example 2 at the vertical incident angle. Calculations show an average reflectance of 96.358% in the 800-2000nm wavelength range, a green luminance value L' = 72.9, and chromaticity coordinates for green (0.3002, 0.5998). The designed green is very close to the standard green chromaticity coordinates (0.3000, 0.6000) used in liquid crystal displays. This embodiment achieves a good green effect while also achieving high reflectivity in the near-infrared band, resulting in a cooling effect.

[0108] Table 2

[0109]

[0110] Example 3

[0111] This embodiment provides a structured color thin film that achieves cooling function based on Fano resonance. The structured color device consists 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) to construct a one-dimensional photonic crystal structure. In this embodiment, the one-dimensional photonic crystal structure adopts a three-layer structure, and the specific thickness of each layer is given in Table 3. Figure 9 This is the reflection spectrum of Example 3 under vertical incidence. Figure 10 This is the chromaticity coordinate diagram of Example 3 at the vertical incident angle. The calculated average reflectance in the 800-2000nm wavelength range is 96.602%, and the blue luminance value L' = 27.7. The chromaticity coordinates of blue are (0.1725, 0.0621), which is very close to the standard blue chromaticity coordinates (0.1500, 0.0600) used in liquid crystal displays. This embodiment achieves good blue effect while also achieving high reflectivity in the near-infrared band, resulting in 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 structured color thin film that achieves cooling functionality based on Fano resonance. The structured color device consists 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 in this embodiment employs a three-layer structure, and the specific thickness of each layer is given in Table 4. Figure 11 This is the reflection spectrum of Example 4 under vertical incidence. Figure 12 This is the chromaticity coordinate diagram of Example 4 at the vertical incident angle. The calculated average reflectance in the 800-2000nm wavelength range is 86.863%, the tristimulus values ​​for cyan are (47.0886, 69.2878, 95.6001), the converted RGB values ​​are (52, 241, 243), the chromaticity coordinates for cyan are (0.2221, 0.3269), and the cyan luminance value L' = 86.6. This example achieves good cyan effect while also achieving high reflectivity in the near-infrared band, resulting in 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 structured color thin film that achieves cooling functionality based on Fano resonance. The structured color device consists 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 in this embodiment employs a three-layer structure, and the specific thickness of each layer is given in Table 5. Figure 13 This is the reflectance spectrum of Example 5 under vertical incidence. Figure 14 This is the chromaticity coordinate diagram of Example 5 at the vertical incident angle. The calculated average reflectance in the 800-2000nm wavelength range is 85.526%, the tristimulus values ​​for magenta are (48.4559, 27.5331, 81.1829), the converted RGB values ​​are (224, 80, 235), the chromaticity coordinates for magenta are (0.3083, 0.1752), and the luminance value L' = 59.5. This embodiment achieves good magenta effect while also achieving high reflectivity in the near-infrared band, thus 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 structured color thin film that achieves cooling function based on Fano resonance. The structured color device consists 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) to construct a one-dimensional photonic crystal structure. In this embodiment, the one-dimensional photonic crystal structure adopts a five-layer structure, and the specific thickness of each layer is given in Table 6. Figure 15 This is the reflection spectrum of Example 6 under vertical incidence. Figure 16 This is the chromaticity coordinate diagram of Example 6 at the vertical incident angle. The calculated average reflectance in the 800-2000nm wavelength range is 93.23%, the tristimulus values ​​for yellow are (69.1297, 80.4566, 7.8377), the converted RGB values ​​are (251, 236, 141), the chromaticity coordinates for yellow are (0.4391, 0.5111), and the yellow luminance value L' = 91.9. This example achieves a good yellow effect while also realizing high reflectivity in the near-infrared band, thus achieving a cooling effect.

[0124] Table 6

[0125]

[0126] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A structural color thin film with cooling function based on Fano resonance, characterized in that, The thin film comprises a structure stacked sequentially from bottom to top: M1DM2AL(HL)^s. The structure of the thin film is asymmetric, where 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 times the layers are stacked, 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. The first metal layer M1 and the second metal layer M2 are made of one of Ag, Ti, Al, Au and Cu. The material of the first dielectric layer D is one or a mixture of at least two of the following: 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. The absorber layer is made of one of the following materials: Ni, Ti, Cr, Fe2O3, Ge, monocrystalline silicon, polycrystalline silicon, Sb2S3, Sb2Se3, VO2, Ge2Sb2Te5, Ge2Sb2Se4Te1, and GeTe. The high refractive index dielectric layer H is made of one of the following materials: Ta2O5, TiO2, HfO2, ZrO2, Nb2O5, La2Ti2O7, Y2O3, ZnS, Si3N4, Bi2O3, CeO2, Cr2O3, MgO, Nd2O3, and ZnO; the low refractive index dielectric layer L is made of one of the following materials: MgF2, SiO2, Al2O3, AlF3, CeF3, LaF3, Na3AlF6, NdF3, BaF2, CaF2, and LiF. The thickness of the first metal layer M1 is greater than 100 nm; The thickness of the second metal layer M2 is between 5-35 nm; The thickness of the first dielectric layer D is between 5 and 1000 nm. The thickness of the absorption layer A is between 1 and 30 nm; The thickness of the low refractive index dielectric layer L ranges from 5 to 1000 nm; The thickness of the high refractive index dielectric layer H ranges from 5 to 1000 nm.

2. The structural color thin film with cooling function based on Fano resonance as described in claim 1, characterized in that, The number of repeated stacking times s = 1 or 2.

3. A method for preparing a structural color thin film with cooling function based on Fano resonance, characterized in that, This method requires providing a structural color thin film with cooling function based on Fano resonance as described in any one of claims 1 to 2, specifically including the following steps: Step 1: The thin film to be deposited has an asymmetric structure, which is: M1DM2AL(HL)^s. The structure of this thin film is asymmetric, where 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. Step 2: Set the total number of layers, the material used in each layer, the thickness of each layer, and the distribution between each layer according to the user's functional requirements, so that the film can present 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, then 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, then the sixth layer is a high refractive index medium layer H, and the seventh layer is a low refractive index medium layer L; repeat the structure of the sixth to seventh layers to set the eighth to the last layer; Step 3: Place a flat object as a substrate into the cavity of the film forming equipment; perform a pre-cleaning treatment on the substrate surface in the reaction chamber to remove surface contaminants; Step 4: Deposit the first layer on the upper surface of the substrate. After the first layer is completely deposited, deposit the second layer on the upper surface of the first layer. After the second layer is completely deposited, deposit the next layer on the upper surface of the second layer. Deposit the layers in sequence until the last layer is deposited to complete the coating. Step 5: Separate the substrate from the first layer to obtain the prepared target film.

4. The method for preparing a structural color thin film with cooling function based on Fano resonance as described in claim 3, characterized in that, The method for cleaning the substrate surface in step 3 is either ion bombardment or high-temperature baking; 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 in step 4 is either physical vapor deposition or chemical vapor deposition.

5. The method for preparing a structural color thin film with cooling function based on Fano resonance as described in claim 3, characterized in that, The substrate material is made of polished glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate, cellulose triacetate, polymethyl methacrylate, polycarbonate / polymethyl methacrylate composite material, polyimide, polypropylene, polyvinyl chloride, polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane elastomer, polytetrafluoroethylene, fluoroethyl propylene, or polydifluoroethylene. The substrate has a release layer material on its upper surface, which separates the substrate from the first layer. The release layer material is a water-soluble fluoride, chloride, or a water-soluble organic material and organic solvent, such as polyvinyl alcohol, acrylic resin, polyvinyl acetate, chloride, or fluoride.

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