An environmentally friendly structural color film with low angle dependence

Abstract

The utility model discloses an environmentally friendly structural color film with low angle dependence. The structure of the structural color film is shown in the following structural formula: G-M-A-silicon-based anti-reflection film stack; wherein G represents a substrate, M represents a metal reflective layer, and A represents a silicon thin film material layer. From bottom to top, it includes a substrate, a metal reflective layer, a silicon thin film material layer, and a silicon-based anti-reflection film stack. Among them, the metal reflective layer provides a high reflectivity value to ensure high brightness, and the silicon thin film material layer uses a silicon thin film loss medium as an absorption layer, which can achieve the same absorption effect as a traditional transparent medium absorption layer with a thinner thickness. The total thickness of the film layer is reduced, and the angle-insensitive performance is significantly improved, and a high-saturation thin film structural color is achieved with a minimum number of structural layers. As an anti-reflection film stack, the silicon-based anti-reflection film stack provides a larger high and low refractive index difference, increases the relative width of the anti-reflection spectral range, reduces the influence of light in other bands, and further improves the purity and saturation of the reflected color.

Description

Technical Field

[0001] The utility model relates to the technical field of structural color films, in particular to an environmentally friendly structural color film with low angle dependence. Background Art

[0002] The beautiful colors of insect shells, butterfly wings, bird feathers and fish scales in nature are the colors produced by the nanoscale microstructures through interference, diffraction and scattering of light, which produce different degrees of reflection of specific wavelengths of incident light. This gorgeous color comes from pigments or structures. The colors produced by pigments are called pigment colors, that is, chemical colors; the colors produced by structures are called structural colors, also known as physical colors. Since chemical colors have the disadvantages of easy fading, not environmentally friendly and poor angular tolerance, structural colors have more application prospects. At present, structural color films are mostly used in the fields of anti-counterfeiting and light display. It is known to form structural color films by stacking materials with different refractive indices, and it is also known to form omnidirectional high-chromaticity structural color films by changing the materials and adjusting the thickness of each layer of materials. However, the existing structural color films require multiple film layers to be stacked, and the thickness of the film layers themselves is also relatively large, resulting in a large overall optical thickness, so the angular tolerance and chromaticity performance are not satisfactory.

[0003] In order to achieve the above technical effects, the existing technology, such as Chinese patent CN109455944A, is usually white in the state of photonic crystal powder, and a photonic crystal film will be formed after orderly self-assembly. When the incident light passes through this photonic crystal film with a periodic structure, due to interference, diffraction and scattering effects, a gorgeous structural color is produced, but this method uses a sulfide film, which is less environmentally friendly. For example, Chinese patent CN 105137518A reports the use of metal / dielectric layer / metal to achieve a reflective color film with low angle dependence, but the inherent absorption of metal in the visible light band will inevitably cause a decrease in reflection efficiency, and it is difficult to achieve high brightness and high saturation colors. For example, Chinese patent CN107340556A reports the realization of an omnidirectional high-chromaticity red structural color film based on a multi-layer metal dielectric film, but heavy metal materials such as chromium and nickel are mostly used in the selection of the absorber layer. Utility Model Content

[0004] In view of this, the purpose of the utility model is to provide an environmentally friendly structural color film with low angle dependence, which can solve the problems of low color brightness, poor saturation, and environmentally unfriendly materials in the background technology.

[0005] According to one aspect of the utility model, an environmentally friendly structural color film with low angle dependence is provided, and the structure of the structural color film is shown in the following structural formula:

[0006] In the GMA-silicon-based anti-reflection film stack formula, G represents the substrate, M represents the metal reflective layer, and A represents the silicon thin film material layer.

[0007] In the above technical solution, a structural color film with low angle dependence is constructed based on silicon-based materials to achieve a structural color film with material safety and environmental protection. From bottom to top, it includes a substrate, a metal reflective layer, a silicon thin film material layer, and a silicon-based anti-reflection film stack. Among them, the metal reflective layer provides a high reflectivity value to ensure high brightness, and the silicon thin film material layer uses a silicon thin film loss medium as an absorption layer, which can achieve the same absorption effect as the traditional transparent medium absorption layer with a thinner thickness. The total thickness of the film layer is reduced, and the angle insensitivity performance is significantly improved. The high-saturation thin film structural color is achieved with the lowest possible number of structural layers, and its thickness is 5nm-20nm. As an anti-reflection film stack, the silicon-based anti-reflection film stack provides a larger high and low refractive index difference. SiO has both a high refractive index and a short-wave high extinction coefficient in the visible light band, which increases the relative width of the anti-reflection spectrum range, reduces the influence of light in other bands, and further improves the purity and saturation of the reflected color. At the same time, silicon is extremely abundant on the earth and is harmless to the human body. Compared with heavy metals such as chromium and nickel and sulfide materials used in other designs, silicon materials are safer, have lower costs, and simpler preparation processes.

[0008] In some embodiments, the silicon-based anti-reflection film stack structure is as follows:

[0009] aL

[0010] In the formula, L represents a low-refractive-index silicon dioxide material layer, H represents a high-refractive-index silicon monoxide material layer, and a and b represent thickness coefficients in units of quarter-wavelength thickness.

[0011] In the above technical solution, an absorption anti-reflection layer is constructed by stacking three layers of silicon dioxide (SiO2), silicon monoxide (SiO) and silicon dioxide (SiO2) to suppress the residual reflection of the sideband and improve the color saturation of the structural color film. SiO has both a high refractive index and a high extinction coefficient in the visible light band. It can be combined with the low refractive index material SiO2 to achieve an interference anti-reflection effect in the short-wave 400-600nm band. The silicon element is extremely abundant on the earth and is harmless to the human body. Compared with heavy metals such as chromium and nickel and sulfide materials used in other designs, silicon materials are safer to use, have lower costs, and have simpler preparation processes.

[0012] In some embodiments, the metal layer is made of a high-reflectivity metal material with a peak reflectivity greater than 90%, and the stacking thickness of the layer ranges from 50 to 200 nm.

[0013] In the above technical solution, one or a combination of gold (Au), silver (Ag), aluminum (Al), copper (Cu) can be selected. This layer is used for brightness control to ensure that the peak reflectivity of the entire multilayer film stack is greater than 90% to achieve higher color brightness.

[0014] In some embodiments, the silicon thin film material layer is a combination of one or both of silicon and amorphous silicon, and the thickness of the layer ranges from 5nm to 20nm. It can achieve the same absorption effect as a traditional transparent medium absorption layer with a thinner thickness, reduce the total thickness of the film layer, and significantly improve the angle insensitivity performance.

[0015] In the above technical solution, silicon is extremely abundant on earth and is harmless to the human body. Compared with heavy metals such as chromium and nickel and sulfide materials used in other designs, silicon materials are safer to use, have lower costs, and are simpler to prepare. The refractive index and extinction coefficient conditions of the silicon material itself are also the reasons for selecting silicon in this technical solution. The refractive index is greater than 4 in the visible light band, which can meet the requirements of color tone control under very thin physical thickness conditions and achieve low-angle effects. The extinction coefficient has higher absorption in short-wave visible light and lower absorption in long-wave visible light, which is suitable for the invention to achieve color control of red, yellow, and purple.

[0016] In some embodiments, the difference in refractive index between the low refractive index silicon dioxide material layer and the high refractive index silicon monoxide material layer is 1.15.

[0017] In the above technical solution, the thickness of the silicon monoxide high refractive index layer is in the range of 60nm-90nm, and the thickness of the silicon dioxide low refractive index layer is in the range of 50-100nm.

[0018] In some embodiments, the refractive index of the outermost low-refractive-index silica material layer is L=1.45, and the thickness of the layer is in the range of 50-100 nm.

[0019] In the above technical solution, the refractive index of the outermost low-refractive-index silicon dioxide material layer is L=1.45, and the thickness of the layer is in the range of 50-100 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the utility model 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 utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1This is a schematic diagram of the film structure of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model;

[0022] Figure 2 Comparison chart of optical constants of several common silicon-based materials;

[0023] Figure 3 A reflection spectrum diagram of a specific example of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model at an incident angle of 0-50°;

[0024] Figure 4 A chromaticity coordinate diagram of a specific example of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model at an incident angle of 0-50°;

[0025] Figure 5 This is a reflection spectrum diagram of a specific example 2 of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model at an incident angle of 0-50°;

[0026] Figure 6 This is a chromaticity coordinate diagram of a specific example 2 of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model at an incident angle of 0-50°;

[0027] Figure 7 This is a reflection spectrum diagram of a specific example 3 of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model at an incident angle of 0-50°;

[0028] Figure 8 This is a chromaticity coordinate diagram of a third specific example of an embodiment of an environmentally friendly structural color film with low angle dependence of the utility model at an incident angle of 0-50°. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is particularly noted that the following embodiments are only used to illustrate the present invention, but do not limit the scope of the present invention. Similarly, the following embodiments are only partial embodiments of the present invention rather than all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The utility model provides an environmentally friendly structural color film with low angle dependence, which can solve the problems of low color brightness, poor saturation, and environmentally unfriendly materials in the background technology.

[0031] Embodiment 1

[0032] See also Figure 1, a structural color thin film multilayer structure with low angle dependence, characterized in that it includes a substrate, a metal reflective layer, an ultra-thin silicon absorption layer, and a silicon-based anti-reflection film stack from bottom to top.

[0033] The substrate of the structural color film described in this embodiment can be selected from one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), stainless steel, K9 glass, calcium fluoride glass, fluoroethylpropylene (FEP), polypropylene (PP), polyvinyl chloride (PVC), and polycarbonate (PC).

[0034] The metal reflective layer of the structural color film described in this embodiment is used for brightness control and can be made of one or a combination of gold (Au), silver (Ag), aluminum (Al), and copper (Cu). It is first deposited on a substrate using a physical vapor deposition method.

[0035] In the structural color film described in this embodiment, the ultra-thin silicon film layer is used for color tone control, wherein the ultra-thin silicon film can be selected from silicon (Si), amorphous silicon (α-Si) or a combination thereof, and is deposited on the metal reflective layer by physical vapor deposition.

[0036] The structural color film described in this embodiment uses a silicon-based anti-reflection film stack for saturation control, and silicon monoxide (SiO) and silicon dioxide (SiO2) are selected. The absorption anti-reflection layer is constructed by stacking three layers of silicon dioxide (SiO2), silicon monoxide (SiO) and silicon dioxide (SiO2) to suppress the sideband residual reflection and improve the color saturation of the structural color film. And physical vapor deposition is used to deposit it on the color tone control unit. Among them, silicon dioxide (SiO2) is first deposited on the ultra-thin silicon film of the color tone control unit, silicon monoxide (SiO) is deposited on silicon dioxide (SiO2) in turn, and finally silicon dioxide (SiO2) is deposited on silicon monoxide (SiO).

[0037] The structural color film described in this embodiment adopts a film layer structure of MA-aLbHaL, where M represents a metal reflective layer, A represents an ultra-thin silicon film material layer, L represents a low-refractive-index silicon dioxide material layer, H represents a high-refractive-index silicon monoxide material layer, and a and b represent thickness coefficients in units of quarter-wavelength thickness. Based on this initial film system structure, a combination of thickness and sequence is optimized according to given color target values ​​or chromaticity and other indicators.

[0038] Among them, quarter wavelength optical thickness (QWOT) is an optical parameter, that is, λ0 / 4 optical thickness, defined as nd, where λ0 represents the reference wavelength, n represents the refractive index of the film layer, and d represents the physical thickness of the film layer. In a regular film system, H or L represents a high refractive index film layer or a low refractive index film layer of QWOT. The above a and b are the proportional coefficients of QWOT. When a and b are both 1, it is a regular film system, otherwise it is an irregular film system. The multilayer film with λ0 / 4 optical thickness alternating between H and L will reduce the reflectivity due to the destructive interference of the reflections of the substrate, film layer, and air, thereby achieving the purpose of anti-reflection.

[0039] The absorption of MA is single-point absorption with a narrow absorption bandwidth. Therefore, it is necessary to add an additional high and low refractive index film pair on the basis of the MA structure to achieve anti-reflection function to further enhance color purity. The residual reflection in the broadband anti-reflection spectral range is mainly determined by the following aspects: 1) the relative width of the anti-reflection spectral range; 2) the refractive index ratio of the high and low refractive index materials; 3) the total optical thickness; 4) the refractive index of the outermost layer. According to Willey's empirical formula:

[0040]

[0041] Wherein, the anti-reflection bandwidth is B = λ max / λ min Indicates; max and λ min They represent the maximum and minimum values ​​of the anti-reflection zone respectively; L is the refractive index of the outermost layer; T is the total thickness of the film system,

[0042] express;

[0043] D represents the difference between the high and low refractive indexes of the film layers other than the outermost layer; in the technical solution of the present invention, in order to achieve the specified broadband anti-reflection effect with the least number of layers, we selected the LHL three-layer thin film structure to construct the broadband anti-reflection film stack to achieve broadband residual reduction reflection in a given band, and the high refractive index material H selected is SiO, with a refractive index of H = 2.6, and the low refractive index material L is SiO2, with a refractive index of L = 1.45. The outermost layer also uses SiO2 as the outer layer material, with a refractive index of L = 1.45, and the high and low refractive index difference D = 1.15. At the same time, SiO is selected as the high refractive index material, and the distribution of the extinction coefficient of SiO in the visible light band of 400-700nm is also considered, and its extinction coefficient is as follows Figure 2 As shown, it has a higher extinction coefficient of 0.6-0.2 at shortwave 400-500nm and a lower extinction coefficient of 0.1-0.01 at longwave 600-700nm, which provides the necessary absorption conditions for achieving shortwave broadband absorption and anti-reflection. According to the anti-reflection bandwidth B required by the design, the stacked LHL thickness is optimized to achieve broadband anti-reflection effect.

[0044] The utility model has the advantages of low cost, environmental friendliness, no need for complex processes, and color that does not change with angle of observation. It has good application scenarios in the fields of light display, color decoration, and anti-counterfeiting. It is expected to replace traditional chemical dyes as a green new coloring strategy, providing a novel implementation solution for green printing technology. The following will explain it with three specific examples.

[0045] One of the specific examples

[0046] like Figure 1 As shown, a red structural color film with low angle dependence is composed of a substrate Sub, a metal reflective layer M silver (Ag), an ultra-thin absorption silicon film material A (a-Si), a high refractive index medium material H (SiO), and a low refractive index medium material L (SiO2). The substrate is made of K9 glass with a thickness of 2 mm and a diameter of 80 mm; the metal layer is made of Ag, which provides a higher reflectivity while also absorbing short waves that have a greater impact on the color purity of red, thereby improving the color purity of red; the absorption layer is made of amorphous silicon, which also has short-wave absorption characteristics. The use of amorphous silicon can further reduce residual reflection and improve color purity; the top absorption layer is made of a three-layer thin film structure SiO2 / SiO X / SiO2 constructs a "W" type anti-reflection film to achieve broadband absorption performance. The specific thickness of each layer is given in the table below. According to the given thickness values, a red structural color film with low angle dependence can be prepared.

[0047] Number of layers Material Physical thickness (nm) 5 <![CDATA[SiO2]]> 80.5 4 SiO 84.5 3 <![CDATA[SiO2]]> 80.5 2 α-Si 13.8 1 Ag 100

[0048] Figure 3 , 4 The following is a reflection spectrum and chromaticity coordinate diagram of a specific example at an incident angle of 0-50°. The red band reflection peak reaches about 97%, the average residual reflectivity of the blue-green band reaches about 2.5%, and the 50% peak transmittance point has a spectrum drift of only 18nm at 0-50°. The visual appearance is still red. At a vertical incident angle, its chromaticity coordinate values ​​are x=0.5499, y=0.3109, and at a 50° incident angle, its chromaticity coordinate values ​​are x=0.5545, y=0.3242. It has a small coordinate change, and the reflected color does not change significantly with the angle change, showing good low-angle dependence.

[0049] Specific example two

[0050] like Figure 1As shown, a golden structural color film with low angle dependence is composed of a substrate Sub, a metal reflective layer M aluminum (Al), an ultra-thin absorption silicon film material A (a-Si), a high refractive index medium material H (SiO), and a low refractive index medium material L (SiO2). The substrate is made of K9 glass with a thickness of 2 mm and a diameter of 80 mm; the metal layer is made of Al, which has a wide reflection band and provides a high reflectivity. At the same time, the metal aluminum material has abundant production and low cost. The absorption layer is made of amorphous silicon, which also has short-wave absorption characteristics. The use of amorphous silicon can further reduce residual reflection and improve color purity; the top absorption layer is made of a three-layer thin film structure SiO2 / SiO X / SiO2 constructs a "W" type anti-reflection film to achieve broadband absorption performance. The specific thickness of each layer is given in the table below. According to the given thickness values, a gold structural color film with low angle dependence can be prepared.

[0051] Number of layers Material Physical thickness (nm) 5 <![CDATA[SiO2]]> 55 4 SiO 70 3 <![CDATA[SiO2]]> 55 2 α-Si 8 1 Al 150

[0052] Figure 5 , 6 The reflection spectrum and chromaticity coordinate diagram of the second specific example at an incident angle of 0-50° are shown. The reflection peak value of the yellow band reaches about 83%, the average residual reflectivity of the blue band 400-480nm reaches about 5%, and the spectral drift of the 50% peak transmittance point at 0-50° is only 16nm, and the visual appearance is still golden yellow. At a vertical incident angle, its chromaticity coordinate values ​​are x=0.4482, y=0.466, and at an incident angle of 50°, its chromaticity coordinate values ​​are x=0.4202, y=0.4521, with a small coordinate change, and the reflected color does not change significantly with the angle change, showing good low-angle dependence.

[0053] Specific example three

[0054] like Figure 1 As shown, a purple-red structural color film with low angle dependence is composed of a substrate Sub, a metal reflective layer M silver (Ag), an ultra-thin absorption silicon film material A (a-Si), a high refractive index medium material H (SiO), and a low refractive index medium material L (SiO2). The substrate is made of K9 glass with a thickness of 2 mm and a diameter of 80 mm; the metal layer is made of Ag, which provides a higher reflectivity while also absorbing short waves that have a greater impact on the color purity of purple, thereby improving the color purity of purple; the absorption layer is made of amorphous silicon, which also has short-wave absorption characteristics. The use of amorphous silicon can further reduce residual reflection and improve color purity; the top absorption layer is made of a three-layer thin film structure SiO2 / SiO X / SiO2 constructs a "W" type anti-reflection film to achieve broadband absorption performance. The specific thickness of each layer is given in the table below. According to the given thickness values, a purple-red structural color film with low angle dependence can be prepared.

[0055] Number of layers Material Physical thickness (nm) 5 SiO2 83 4 SiO 69 3 SiO2 83 2 α-Si 14.3 1 Al 120

[0056] Figure 7 , 8 This is the reflection spectrum and chromaticity coordinate diagram of the third specific example at an incident angle of 0-50°. The reflection peak reaches about 80%, the reflectivity of the blue band reaches about 20%, and the 50% peak transmittance point has a spectrum drift of only 17nm at 0-50°, which is visually purple-red. At a vertical incident angle, its chromaticity coordinate values ​​are x=0.32, y=0.166, and at a 50° incident angle, its chromaticity coordinate values ​​are x=0.38, y=0.195, with a small coordinate change, and the reflected color does not change significantly with the angle change, showing good low-angle dependence.

[0057] The above descriptions are only some embodiments of the present invention, and do not 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 used in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An environmentally friendly structural color film with low angle dependence, characterized in that: The structure of the structural color film is shown in the following structural formula: GMA-Silicon-based anti-reflection film stack In the formula, G represents the substrate, M represents the metal reflective layer, and A represents the silicon thin film material layer.

2. The environmentally friendly structural color film with low angle dependence according to claim 1, characterized in that: The silicon-based anti-reflection film stack structure is as follows: aL In the formula, L represents a low-refractive-index silicon dioxide material layer, H represents a high-refractive-index silicon monoxide material layer, and a and b represent thickness coefficients in units of quarter-wavelength thickness.

3. The environmentally friendly structural color film with low angle dependence according to claim 1, characterized in that: The metal layer is made of a high-reflectivity metal material with a peak reflectivity greater than 90%, and the stacking thickness is 50-200nm.

4. The environmentally friendly structural color film with low angle dependence according to claim 1, characterized in that: The silicon thin film material layer is made of one of silicon and amorphous silicon.

5. The environmentally friendly structural color film with low angle dependence according to claim 2, characterized in that: The difference in refractive index between the low-refractive-index silicon dioxide material layer and the high-refractive-index silicon monoxide material layer is 1.

15.

6. The environmentally friendly structural color film with low angle dependence according to claim 2, characterized in that: The refractive index of the outermost low-refractive-index silica material layer is L=1.45.

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