Near-infrared high-reflectance structural color filter and its preparation method

Abstract

This invention provides a near-infrared high-reflectivity structural color filter and its fabrication method, relating to the field of optical technology. The near-infrared high-reflectivity structural color filter includes a substrate and, sequentially formed on the substrate, a reflective layer, a first dielectric layer, a first absorption layer, a second dielectric layer, a second absorption layer, and an anti-reflective layer. The reflective layer, the first dielectric layer, and the first absorption layer constitute a first optical resonant cavity, and the first absorption layer, the second dielectric layer, and the second absorption layer constitute a second optical resonant cavity. Both the first and second absorption layers exhibit lower absorption rates for visible light within the target color wavelength range than for visible light within the non-target color wavelength range, and their absorption rates for near-infrared light are lower than a preset absorption rate threshold. By employing two continuous asymmetric optical resonant cavities and a top anti-reflective layer, high-purity and high-brightness colors are achieved in the visible light range, and cooling functionality is achieved using the high reflectivity of the near-infrared band. Furthermore, the process is low-cost and simple.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a near-infrared high-reflectivity structural color filter and its preparation method. Background Technology

[0002] Structural color, also known as physical color or interference color, is a type of color produced by physical phenomena such as interference and diffraction of light within or on the micro- and nano-structures of an object. This color is not determined by pigments, but rather depends on the effect of the fine structure within or on the surface of the material on incident light. In recent years, structural color has attracted widespread attention as a powerful alternative to traditional pigments and dyes, and is suitable for various applications including color display / printing, information encryption, colorimetric sensors, and optical decoration.

[0003] The near-infrared region (i.e., the spectral region from 800 to 1600 nm), which is outside the visible light spectrum, accounts for most of the heat generated by sunlight. Therefore, materials / systems with high near-infrared reflectivity can be widely used in roof coatings, smart windows, and vehicle coatings to mitigate the negative effects of heat conduction. For aesthetic purposes, there is an urgent need to integrate high-performance structural color devices into near-infrared high-reflectivity materials / systems.

[0004] Currently, the main methods for integrating structural color devices into near-infrared high reflectivity materials / systems include:

[0005] 1. A radiation cooling coating is obtained by coating an organic solvent containing a mixture of nano-Al2O3 particles and ordinary glass particles;

[0006] 2. Cooling coating prepared using the 2D silica grating structure on top of ZnO / Ag / ZnO;

[0007] 3. Cooling coatings prepared using ceramic materials such as alumina (Al2O3) and silicon dioxide (SiO2);

[0008] 4. Cooling coating prepared using porous polyethylene (PE) film;

[0009] 5. Achieve a colored cooling coating by adding an FP (Fabry-Pérot cavity) structure to the existing white / silver solar cooler;

[0010] 6. The bottom layer is coated with a radiation cooling coating, and the top layer uses phosphor to obtain color and achieve a cooling effect.

[0011] However, the above methods are complex in process, and most of them have only one color and are not aesthetically pleasing. In addition, organic materials cause great environmental pollution, which is not conducive to environmental protection. Furthermore, materials such as PE may be affected by factors such as ultraviolet rays, temperature changes and humidity when exposed to the natural environment for a long time, which will lead to a decline in material performance and thus poor device stability. Although the colored cooling coating using the FP cavity structure is aesthetically pleasing, the structural color obtained by simply using layered thin films can only achieve absorption in a narrow wavelength range, which greatly limits the purity of the generated structural color. Summary of the Invention

[0012] The purpose of this invention is to provide a near-infrared high-reflectivity structural color filter and its preparation method, so as to achieve high-purity and high-brightness colors in the visible light range, and to achieve a cooling function by utilizing the high reflectivity of the near-infrared band. The process is low-cost and simple.

[0013] In a first aspect, the present invention provides a near-infrared high reflectance structural color filter, comprising a substrate and a reflective layer, a first dielectric layer, a first absorption layer, a second dielectric layer, a second absorption layer and an anti-reflection layer sequentially formed on the substrate;

[0014] The reflective layer, the first dielectric layer, and the first absorption layer constitute the first optical resonant cavity, and the first absorption layer, the second dielectric layer, and the second absorption layer constitute the second optical resonant cavity. The absorption rate of the first absorption layer and the second absorption layer for visible light in the target color wavelength range is less than the absorption rate for visible light in the non-target color wavelength range, and the absorption rate for near-infrared light is less than a preset absorption rate threshold.

[0015] Furthermore, the reflectivity of the reflective layer is greater than 90%.

[0016] Furthermore, the reflective layer can be made of materials such as aluminum, copper, gold, platinum, palladium, or silver.

[0017] Furthermore, the reflective layer is made of aluminum, and its thickness is greater than 70nm.

[0018] Furthermore, the materials of the first dielectric layer, the second dielectric layer, and the antireflective layer all include at least one of niobium titanium oxide, silicon dioxide, silicon oxynitride, aluminum oxide, titanium dioxide, niobium pentoxide, tantalum pentoxide, zirconium oxide, yttrium oxide, hafnium dioxide, silicon nitride, zinc selenide, tungsten oxide, and zinc sulfide.

[0019] Furthermore, both the first and second absorption layers have a higher reflectivity for visible light within the target color wavelength range than for visible light within the non-target color wavelength range.

[0020] Furthermore, both the first and second absorption layers are made of germanium or silicon.

[0021] Furthermore, the reflective layer is made of aluminum, while the first and second absorption layers are both made of germanium.

[0022] Furthermore, the materials of the first dielectric layer, the second dielectric layer, and the anti-reflective layer are all silicon nitride.

[0023] In a second aspect, the present invention also provides a method for preparing a near-infrared high-reflectance structural color filter as described in the first aspect, comprising:

[0024] A reflective layer is formed on the substrate;

[0025] A first dielectric layer is formed on the reflective layer;

[0026] A first absorption layer is formed on the first dielectric layer;

[0027] A second dielectric layer is formed on the first absorber layer;

[0028] A second absorption layer is formed on the second dielectric layer;

[0029] An anti-reflective layer is formed on the second absorption layer.

[0030] The near-infrared high-reflectance structural color filter and its preparation method provided by the present invention include a substrate and a reflective layer, a first dielectric layer, a first absorption layer, a second dielectric layer, a second absorption layer, and an anti-reflection layer sequentially formed on the substrate; the reflective layer, the first dielectric layer, and the first absorption layer constitute a first optical resonant cavity, and the first absorption layer, the second dielectric layer, and the second absorption layer constitute a second optical resonant cavity; the absorption rate of the first absorption layer and the second absorption layer for visible light in the target color wavelength range is less than the absorption rate for visible light in the non-target color wavelength range, and the absorption rate for near-infrared light is less than a preset absorption rate threshold. This design employs two continuous asymmetric optical resonant cavities and a top anti-reflection layer. The two continuous asymmetric optical resonant cavities generate constructive interference on visible light within the desired target color wavelength range, while optically absorbing visible light within the non-target color wavelength range. Through multi-cavity resonance enhancement, the reflection of visible light within the non-target color wavelength range is effectively suppressed. Furthermore, the first and second absorption layers have low absorption rates for near-infrared light, ensuring high reflectivity in the near-infrared region. Therefore, this near-infrared high-reflectivity structural color filter achieves high-purity and high-brightness colors within the visible light range, and utilizes the high reflectivity of the near-infrared band to achieve a cooling function. Simultaneously, this multilayer thin-film structure is easy to fabricate, inexpensive, and simple to process. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of a near-infrared high-reflectance structural color filter provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of another near-infrared high-reflectance structural color filter provided in an embodiment of the present invention;

[0034] Figure 3 A cross-sectional view of a near-infrared high-reflectance structural color filter provided in an embodiment of the present invention;

[0035] Figure 4 The reflection spectrum corresponding to a blue near-infrared high-reflectance structural color filter provided in an embodiment of the present invention;

[0036] Figure 5 The reflection spectrum corresponding to a green near-infrared high-reflectance structural color filter provided in an embodiment of the present invention;

[0037] Figure 6 The reflection spectrum corresponding to a red near-infrared high-reflectance structural color filter provided in an embodiment of the present invention;

[0038] Figure 7 Three color samples observed from four different angles provided in embodiments of the present invention;

[0039] Figure 8 This is a schematic flowchart illustrating a method for preparing a near-infrared high-reflectance structural color filter according to an embodiment of the present invention.

[0040] Icons: 101-Substrate; 102-Reflective layer; 103-First dielectric layer; 104-First absorption layer; 105-Second dielectric layer; 106-Second absorption layer; 107-Anti-reflective layer. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] By constructing arrays of subwavelength nanostructures ranging from planar thin films to dielectrics or metals, unique colors with a wide color gamut have been achieved. Compared to colors obtained from nanostructures that require complex and expensive photolithography processes, structural colors generated by stacking multilayer thin films can be prepared using methods such as vacuum deposition or electrochemical deposition, which are low-cost and simple to process, thus possessing greater commercial value.

[0043] Structural colors obtained using layered thin films can only achieve absorption within a narrow wavelength range, thus greatly limiting the purity of the generated structural colors. To obtain high-purity reflected colors, some experimental solutions have been proposed, such as using high-loss metals or adding FP resonant cavities to broaden the absorption bandwidth. However, the color purity of these devices is still limited by the surrounding wavelengths; alternatively, ultrathin bilayer dielectrics can be used as effective ideal absorbers, and ultrathin organic dye layers can be incorporated into the FP cavity structure to enhance the purity of the reflected colors, but the color tuning process is cumbersome, and the use of organic dyes also reduces the cooling effect in the near-infrared band.

[0044] Based on this, the near-infrared high-reflectance structural color filter and its preparation method provided by the embodiments of the present invention can achieve high-purity and high-brightness colors in the visible light range, and achieve a cooling function in the near-infrared region, with low cost and simple process.

[0045] To facilitate understanding of this embodiment, a near-infrared high-reflectance structural color filter disclosed in this embodiment of the invention will first be described in detail.

[0046] like Figure 1 As shown, an embodiment of the present invention provides a near-infrared high reflectance structural color filter comprising: a substrate 101 and a reflective layer 102, a first dielectric layer 103, a first absorption layer 104, a second dielectric layer 105, a second absorption layer 106 and an anti-reflection layer 107 sequentially formed on the substrate 101.

[0047] The reflective layer 102, the first dielectric layer 103, and the first absorption layer 104 constitute a first optical resonant cavity, while the first absorption layer 104, the second dielectric layer 105, and the second absorption layer 106 constitute a second optical resonant cavity. Both the first absorption layer 104 and the second absorption layer 106 have lower absorption rates for visible light within the target color wavelength range than for visible light within the non-target color wavelength range, and their absorption rates for near-infrared light are lower than a preset absorption rate threshold.

[0048] Specifically, the substrate 101 forms the basis of the near-infrared high-reflectivity structural color filter, providing physical support. A reflective layer 102 on top of the substrate 101 provides high reflectivity. A first dielectric layer 103 and a second dielectric layer 105 serve as spacers. A first absorption layer 104 and a second absorption layer 106 absorb wavelengths outside the target color band, i.e., absorb visible light outside the target color wavelength range, improving color purity; simultaneously, they have low absorption rates for near-infrared light to ensure high near-infrared reflectivity. An anti-reflective layer 107 is the outermost layer (i.e., the top) of the near-infrared high-reflectivity structural color filter. By sequentially combining these layers, the near-infrared high-reflectivity structural color filter achieves high-purity and high-brightness colors, as well as cooling in the near-infrared region, while maintaining good optical performance and environmental adaptability. Different colors can be achieved by changing the thickness of each film (including the first dielectric layer 103, the first absorption layer 104, the second dielectric layer 105, the second absorption layer 106, and the anti-reflective layer 107).

[0049] The target color wavelength range mentioned above refers to the visible light wavelength range corresponding to the colors that the near-infrared high-reflectance structural color filter needs to present. For example, the target color wavelength range for red is 600 to 750 nm, for green it is 495 to 570 nm, and for blue it is 450 to 495 nm. It should be noted that the target color wavelength range here is only an example; in actual implementation, the target color wavelength range will vary depending on the material and / or thickness of each thin film. The preset absorption rate threshold mentioned above can be set according to actual needs and is not limited here.

[0050] The aforementioned near-infrared high-reflectivity structural color filter employs two continuous asymmetric optical resonant cavities (i.e., the first optical resonant cavity and the second optical resonant cavity) and a top anti-reflection layer 107. The two continuous asymmetric optical resonant cavities generate constructive interference on visible light within the desired target color wavelength range and optically absorb visible light within the non-target color wavelength range. Through multi-cavity resonance enhancement absorption, the reflection of visible light within the non-target color wavelength range is effectively suppressed. Furthermore, the first absorption layer 104 and the second absorption layer 106 have low absorption rates for near-infrared light, ensuring high reflectivity of near-infrared light. Therefore, this near-infrared high-reflectivity structural color filter achieves high-purity and high-brightness colors within the visible light range and utilizes the high reflectivity of the near-infrared band to achieve a cooling function. Simultaneously, this multilayer thin-film structure is easy to fabricate, inexpensive, and simple to process.

[0051] Optionally, the substrate 101 can be made of materials such as quartz, silicon, or glass. It has good mechanical strength and flatness, which can ensure the uniformity of the reflective layer 102.

[0052] Optionally, in order to ensure high color brightness, the reflectivity of the aforementioned reflective layer 102 is greater than 90%.

[0053] Optionally, the reflective layer 102 can be a metal layer, and the material of the reflective layer 102 can include aluminum, copper, gold, platinum, palladium, or silver, etc. These materials all have high reflectivity in the visible and near-infrared spectral ranges.

[0054] Furthermore, the reflective layer 102 is made of aluminum, and its thickness is greater than 70 nm, for example, 100 nm. This ensures that the reflective layer 102 has a reflectivity of over 90%, thereby guaranteeing high color brightness; at the same time, the reflective layer 102 has stable chemical properties and low cost.

[0055] Optionally, the materials of the first dielectric layer 103, the second dielectric layer 105, and the antireflective layer 107 all include at least one of niobium titanium oxide, silicon dioxide, silicon oxynitride, aluminum oxide, titanium dioxide, niobium pentoxide, tantalum pentoxide, zirconium oxide, yttrium oxide, hafnium dioxide, silicon nitride, zinc selenide, tungsten oxide, and zinc sulfide. Aluminum oxide, silicon nitride, and silicon dioxide are easy to prepare; titanium dioxide, zirconium oxide, zinc selenide, and zinc sulfide have high refractive indices and are angle-insensitive (here, the angle refers to the angle between the line of sight and the normal to the filter surface). It should be noted that the materials of the first dielectric layer 103, the second dielectric layer 105, and the antireflective layer 107 can be the same or different, and are not limited to the materials mentioned above.

[0056] Optionally, in order to further improve the purity of the color, both the first absorption layer 104 and the second absorption layer 106 have a higher reflectivity for visible light in the target color wavelength range than for visible light in the non-target color wavelength range.

[0057] Optionally, the materials of the first absorption layer 104 and the second absorption layer 106 can both include germanium or silicon. Germanium's optical loss in the visible light range helps absorb unwanted reflections, thereby generating high-purity colors; and it ensures high NIR (Near-Infrared) reflectivity because germanium has a low absorption rate in the long-wavelength range above 800 nanometers, meaning it has high transparency relative to the near-infrared band.

[0058] Each layer of the aforementioned near-infrared high-reflectivity structural color filter can be prepared using electron beam evaporation, inductively coupled plasma-enhanced vapor deposition, thermal evaporation, or magnetron sputtering, or a combination of these methods. It should be noted that the embodiments of this invention do not limit the preparation equipment for each layer; in other embodiments, chemical vapor deposition may also be used.

[0059] Optionally, the material of the reflective layer 102 is aluminum, and the material of the first absorption layer 104 and the second absorption layer 106 is germanium. The reflective layer 102, the first absorption layer 104 and the second absorption layer 106 are all prepared using an electron beam evaporation device or a thermal evaporation device.

[0060] Furthermore, the materials of the first dielectric layer 103, the second dielectric layer 105, and the antireflective layer 107 are all silicon nitride, and all three layers are prepared using inductively coupled plasma-enhanced vapor deposition (ICP-CVD). This preparation process is simple, low-cost, and produces good cleanliness and smoothness.

[0061] In one possible implementation, such as Figure 2 and Figure 3 As shown, the aforementioned near-infrared high-reflectivity structural color filter can be obtained as follows: using an electron beam evaporation device and an inductively coupled plasma-enhanced vapor deposition device, a dielectric-absorbent layer-dielectric-absorbent layer-dielectric-metal (DADADM) thin film structure is prepared on a quartz substrate in the following order from top to bottom: the metal layer is a 100nm thick aluminum (Al) layer deposited on the quartz substrate, which serves as the reflective layer. Al is chosen as the bottom layer because it has high reflectivity in the visible and near-infrared spectral ranges. Silicon nitride (Si3N4) is chosen as the dielectric layer because of its high refractive index and is used as the spacer layer and the top anti-reflection (AR) layer. Germanium (Ge) is used as the absorbent layer. Ge is chosen because: (1) its optical loss in the visible light range helps to absorb unwanted reflections, thereby generating high-purity colors; (2) it ensures high NIR reflectivity because it has high transparency in the long-wavelength range above 800nm. Al and Ge were prepared using electron beam evaporation, and Si3N4 was prepared using inductively coupled plasma-enhanced vapor deposition (ICP-VEDS). This process is simple, low-cost, and produces good cleanliness and smoothness. Constructive interference is generated for the desired wavelength in two continuous asymmetric FP cavities, while non-target color wavelengths are optically absorbed through an absorption layer.

[0062] In this embodiment of the invention, a high-purity and high-brightness near-infrared high-reflectivity structural color filter is achieved by using two consecutive asymmetric FP cavities and a top anti-reflection layer. Different colors are obtained by adjusting the film thickness. The semiconductor material (Ge) within the filter acts as an absorption layer with different functions in different wavelength regions: in the visible light range, absorption is enhanced through multi-cavity resonance, effectively suppressing unwanted reflections and producing high-purity RGB colors with a peak reflectivity exceeding 70%; the intrinsic low-loss characteristics in the wavelength >800nm ​​region ensure broadband reflection throughout the near-infrared range, with an average efficiency greater than 80%. Furthermore, this near-infrared high-reflectivity structural color filter maintains color consistency and high NIR reflectivity within an angular range of ±50° (blue and red) and ±40° (green), thus achieving both aesthetic appeal and near-infrared cooling functionality.

[0063] Furthermore, this near-infrared high-reflectivity structural color filter is inexpensive, simple to manufacture, and easier to apply widely, especially in decoration and solar coolers where it has great application potential.

[0064] For example, the film thicknesses corresponding to the three colors are shown in Table 1 below.

[0065] Table 1

[0066]

[0067] Different colors require different film thicknesses, and the film thickness value can be adjusted within ±2nm to ensure color purity.

[0068] Figure 4 The reflectance spectrum corresponding to a blue near-infrared high-reflectance structural color filter is shown. Figure 5 The reflectance spectrum of a green near-infrared high-reflectance structural color filter is shown. Figure 6 The reflection spectrum corresponding to a red near-infrared high-reflectance structural color filter is shown, such as... Figures 4 to 6 As shown, the experimental results are in good agreement with the simulation results. The peak corresponding to blue light is around 450nm, the peak corresponding to green light is around 500nm, and the peak corresponding to red light is 600nm and above (but near-infrared light is not perceptible to the human eye).

[0069] like Figure 7 As shown, among the three color samples observed at four different angles, blue and red maintained their color within an angle range of ±50°, while green maintained its color within an angle range of ±40°.

[0070] This invention also provides a method for preparing the above-mentioned near-infrared high-reflectance structural color filter, see [link to relevant documentation]. Figure 8The diagram shows a process for preparing a near-infrared high-reflectance structural color filter. The preparation method mainly includes the following steps S801 to S806:

[0071] Step S801: Form a reflective layer on the substrate;

[0072] Step S802: A first dielectric layer is formed on the reflective layer;

[0073] Step S803: A first absorption layer is formed on the first dielectric layer;

[0074] Step S804: A second dielectric layer is formed on the first absorber layer;

[0075] Step S805: A second absorption layer is formed on the second dielectric layer;

[0076] Step S806: An anti-reflective layer is formed on the second absorption layer.

[0077] The preparation method provided in this embodiment has the same implementation principle and technical effect as the aforementioned near-infrared high reflectance structural color filter embodiment. For the sake of brevity, any parts of the preparation method not mentioned in the embodiment can be referred to the corresponding content in the aforementioned near-infrared high reflectance structural color filter embodiment.

[0078] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0079] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A near-infrared high-reflectance structural color filter, characterized in that, It includes a substrate and a reflective layer, a first dielectric layer, a first absorption layer, a second dielectric layer, a second absorption layer, and an anti-reflective layer sequentially formed on the substrate; The reflective layer, the first dielectric layer, and the first absorption layer constitute a first optical resonant cavity, and the first absorption layer, the second dielectric layer, and the second absorption layer constitute a second optical resonant cavity; the absorption rate of the first absorption layer and the second absorption layer for visible light in the target color wavelength range is less than the absorption rate for visible light in the non-target color wavelength range, and the absorption rate for near-infrared light is less than a preset absorption rate threshold. Both the first absorption layer and the second absorption layer have a higher reflectivity for visible light within the target color wavelength range than for visible light within the non-target color wavelength range. The reflective layer is made of aluminum, and both the first and second absorption layers are made of germanium.

2. The near-infrared high-reflectance structural color filter according to claim 1, characterized in that, The reflective layer has a reflectivity greater than 90%.

3. The near-infrared high-reflectance structural color filter according to claim 2, characterized in that, The reflective layer may be made of aluminum, copper, gold, platinum, palladium, or silver.

4. The near-infrared high-reflectance structural color filter according to claim 3, characterized in that, The reflective layer is made of aluminum and has a thickness greater than 70 nm.

5. The near-infrared high-reflectance structural color filter according to claim 1, characterized in that, The materials of the first dielectric layer, the second dielectric layer, and the antireflective layer all include at least one of niobium titanium oxide, silicon dioxide, silicon oxynitride, aluminum oxide, titanium dioxide, niobium pentoxide, tantalum pentoxide, zirconium oxide, yttrium oxide, hafnium dioxide, silicon nitride, zinc selenide, tungsten oxide, and zinc sulfide.

6. The near-infrared high-reflectance structural color filter according to claim 1, characterized in that, The materials of the first dielectric layer, the second dielectric layer, and the anti-reflective layer are all silicon nitride.

7. A method for preparing a near-infrared high-reflectance structural color filter as described in any one of claims 1-6, characterized in that, include: The reflective layer is formed on the substrate; The first dielectric layer is formed on the reflective layer; The first absorption layer is formed on the first dielectric layer; The second dielectric layer is formed on the first absorption layer; The second absorption layer is formed on the second dielectric layer; The anti-reflective layer is formed on the second absorption layer.

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