Omnidirectional structural color microstructures comprising titanium dioxide

Abstract

A reflective omnidirectional structural color multilayer film having a reflective core layer; an amorphous phase TiO2 dielectric layer extending on the reflective core layer; a metal absorber layer extending over the dielectric layer; and a dielectric outer layer extending over the metal absorber layer. The multilayer film reflects a single narrowband visible light when exposed to broadband electromagnetic radiation, and a color shift of the single narrowband visible light measured in a Lab color space is less than 30 DEG when the multilayer film is exposed to broadband electromagnetic radiation and viewed from an angle between 0 DEG and 45 DEG with respect to a normal direction to an outer surface of the multilayer film.

Description

Related Applications

[0001] This international application claims priority to U.S. patent application No. 17 / 886,768, filed on August 12, 2022, which is incorporated herein by reference. Technical Field

[0002] The present application relates to multilayer thin film structures, and in particular to multilayer thin film structures comprising titanium dioxide, which exhibit minimal or unnoticeable color shifting when exposed to broadband electromagnetic radiation and viewed from different angles. Background Art

[0003] Pigments made from multilayer structures are known. In addition, pigments that exhibit or provide high chromaticity omnidirectional structural colors are also known. However, forming multilayer structures from certain materials can be difficult because the deposition techniques used to deposit the various materials can negatively affect previously deposited materials. In addition, certain deposition techniques can be costly and time consuming, making it difficult to achieve commercially viable multilayer structures.

[0004] It should be understood that the color produced by a multilayer film structure depends on the materials used as the individual layers, the position of the materials within the multilayer film structure, and the properties of the individual layers (e.g., thickness). Therefore, small changes in the design of the multilayer film structure can have a significant impact on the color produced by the multilayer film structure. However, conventional deposition techniques are not always effective in depositing the required layers within the multilayer film structure to achieve the optimal combination of omnidirectional multilayer films. Summary of the invention

[0005] According to an embodiment, a multilayer film that reflects omnidirectional structural color includes: a reflective core layer; an amorphous TiO2 dielectric layer extending on the reflective core layer; a metal absorption layer extending on the amorphous TiO2 dielectric layer; and a dielectric outer layer extending on the metal absorption layer, wherein the multilayer film reflects a single narrowband visible light when exposed to broadband electromagnetic radiation, and the single narrowband visible light includes: when the multilayer film is exposed to broadband electromagnetic radiation and observed from an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer film, the color shift of the single narrowband visible light measured in the Lab color space is less than 30°.

[0006] In some embodiments, a multilayer film that reflects omnidirectional structural color includes: a reflective core layer; a protective layer encapsulating the reflective core layer; an amorphous TiO2 dielectric layer extending on at least a portion of the protective layer; a metal absorption layer extending on the amorphous TiO2 dielectric layer; and a dielectric outer layer extending on the metal absorption layer, wherein the multilayer film reflects a single narrowband visible light when exposed to broadband electromagnetic radiation, and the single narrowband visible light includes: when the multilayer film is exposed to broadband electromagnetic radiation and observed at an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer film, the color shift of the single narrowband visible light measured in the Lab color space is less than 30°.

[0007] In some embodiments, a multilayer film that reflects omnidirectional structural color includes: a reflective core layer; a protective layer encapsulating the reflective core layer; an amorphous TiO2 dielectric layer extending on at least a portion of the protective layer; a barrier layer extending on the amorphous TiO2 layer, a metal absorption layer extending on the barrier layer; and a dielectric outer layer extending on the metal absorption layer, wherein the multilayer film reflects a single narrowband visible light when exposed to broadband electromagnetic radiation, and the single narrowband visible light includes: when the multilayer film is exposed to broadband electromagnetic radiation and observed at an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer film, the color shift of the single narrowband visible light measured in the Lab color space is less than 30°.

[0008] In some embodiments, a multilayer film that reflects omnidirectional structural color includes: a reflective core layer; an amorphous TiO2 dielectric layer extending on at least a portion of the reflective core layer; a barrier layer extending on the amorphous TiO2 dielectric layer; a metal absorption layer extending on the barrier layer; and a dielectric outer layer extending on the metal absorption layer, wherein the multilayer film reflects a single narrowband visible light when exposed to broadband electromagnetic radiation, and the single narrowband visible light includes: when the multilayer film is exposed to broadband electromagnetic radiation and observed at an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer film, the color shift of the single narrowband visible light measured in the Lab color space is less than 30°.

[0009] According to other embodiments, the method of forming a multilayer thin film includes: depositing an amorphous TiO2 dielectric layer on a reflective core layer by CVD or ALD; depositing a metal absorption layer on the amorphous TiO2 dielectric layer by ALD; and depositing a dielectric outer layer on the metal absorption layer by CVD or ALD.

[0010] In some embodiments, the method of forming a multilayer thin film includes: depositing a protective layer on a reflective core layer by a wet chemical process; depositing an amorphous TiO2 dielectric layer on the protective layer by CVD or ALD; depositing a metal absorption layer on the amorphous TiO2 dielectric layer by ALD; and depositing a dielectric outer layer on the metal absorption layer by CVD or ALD.

[0011] In some embodiments, the method of forming a multilayer thin film includes: depositing a protective layer on a reflective core layer by a wet chemical process; depositing an amorphous TiO2 dielectric layer on the protective layer by CVD or ALD; depositing a barrier layer on the amorphous TiO2 dielectric layer; depositing a metal absorption layer on the barrier layer by ALD; and depositing a dielectric outer layer on the metal absorption layer by CVD or ALD.

[0012] According to other embodiments, the method of forming a multilayer thin film includes: depositing an amorphous TiO2 dielectric layer on a reflective core layer by CVD or ALD; depositing a barrier layer on the amorphous TiO2 dielectric layer by ALD; depositing a metal absorption layer on the barrier layer by ALD; and depositing a dielectric outer layer on the metal absorption layer by CVD or ALD.

[0013] Additional features and advantages will be set forth in the detailed description that follows, and in part will be apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the following detailed description, claims, and accompanying drawings.

[0014] It should be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate various embodiments described herein and, together with the description, serve to explain the principles and operation of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A and Figure 1B is a schematic cross-section of a multilayer film structure according to embodiments disclosed and described herein;

[0016] Figure 2A depicts a multilayer film having a dielectric layer extending over a reflective core layer used in a multilayer film design;

[0017] Figure 2B depicts a multilayer film having a semiconductor absorber layer extending over a reflective core layer used in a multilayer film design;

[0018] Figure 2C depicts a multilayer film having a dielectric absorber layer extending over a reflective core layer used in a multilayer film design according to one or more embodiments shown and described herein;

[0019] Figure 3 Depicted Figures 2A-2C Reflection characteristics of the multilayer film shown in the Lab color space;

[0020] Figure 4A Depicted in a graphical manner Figure 2A The relationship between the chromaticity and hue values ​​of the multilayer films shown in and the dielectric layer thickness;

[0021] Figure 4B Depicted in a graphical manner Figure 2B The relationship between the chromaticity and hue values ​​of the multilayer films shown in and the thickness of the semiconductor absorber layer;

[0022] Figure 4C Depicted in a graphical manner Figure 2C The relationship between the chromaticity and hue values ​​of the multilayer film shown in and the thickness of the dielectric absorber layer;

[0023] Figure 5 is a magnified image of a rutile phase TiO2 dielectric layer deposited on a protective layer;

[0024] Figure 6 A magnified image of a rutile phase TiO2 dielectric layer deposited on a protective layer, a metal absorber layer deposited on the rutile phase TiO2 dielectric layer, and a dielectric outer layer deposited on the metal absorber layer;

[0025] Figure 7 is a magnified image of an amorphous TiO2 dielectric layer deposited on a protective layer, a metal absorber layer deposited on the amorphous TiO2 dielectric layer, and a dielectric outer layer deposited on the metal absorber layer;

[0026] Figure 8 depicts a multilayer film having a dielectric layer extending over a substrate layer and exposed to electromagnetic radiation at an angle θ relative to a normal to an outer surface of the dielectric layer;

[0027] Figures 9A to 9E graphically depicting reflectance curves of embodiments provided herein; and

[0028] Figures 10A to 10F Reflectance curves for the examples provided herein are graphically depicted. DETAILED DESCRIPTION

[0029] The present disclosure provides a structure that produces omnidirectional structural colors. The structure that produces omnidirectional structural colors has the form of a multilayer film (also referred to herein as a multilayer stack) that reflects narrowband electromagnetic radiation in the visible spectrum and has a small or inconspicuous color shift when the multilayer film is observed from an angle between 0 and 45 degrees. The multilayer film can be used as a pigment in a composition (e.g., a paint composition), a continuous film on a structure, etc.

[0030] Preparing omnidirectional structural color multilayer films can be a complex and expensive process, in part because very tight control over layer thickness is required. Deposition methods used to deposit the layers can vary in complexity and cost, depending on the materials that make up a given layer and the desired thickness of said layer. Therefore, different materials that can be deposited by different deposition techniques are needed.

[0031] However, it can be challenging to deposit layers directly onto a reflective core layer (e.g., an aluminum (Al) reflective core layer) by less expensive wet chemical methods because these methods require highly acidic or alkaline conditions. Furthermore, depositing precisely controlled ultra-thin absorber layers is challenging in addition to vacuum coating methods. In the present disclosure, a combination of deposition methods is used to reduce costs and still achieve the desired multilayer thin film structure. Using TiO2 as a dielectric material allows manufacturers to use a combination of wet chemical methods, atomic layer deposition (ALD) (e.g., fluidized bed ALD), and chemical vapor deposition (CVD) (e.g., fluidized bed CVD). For example, ALD can accurately deposit thin layers, but ALD is costly and time consuming. CVD is less expensive and less time consuming than ALD, but is not as precise as ALD and is not well suited for depositing very thin layers. Wet chemical methods are relatively fast and inexpensive, but they are not suitable for depositing very thin layers and have the problems of using acidic or alkaline conditions discussed above. Thus, a combination of ALD, CVD, and wet chemical methods can be used in embodiments using TiO2 dielectric materials to form multilayer thin films at lower cost and higher efficiency than using ALD alone.

[0032] The multilayer film structures described herein can be used to omnidirectionally reflect wavelengths of visible light over a range of incident or viewing angles (e.g., hues between 0° and 120°). It should be understood that the terms "electromagnetic wave," "electromagnetic radiation," and "light" as used herein can interchangeably refer to light of various wavelengths incident on the multilayer film structures, and such light can have wavelengths in the ultraviolet (UV), infrared (IR), and visible portions of the electromagnetic spectrum.

[0033] Reference now Figure 1A The multilayer film 100 according to the embodiments disclosed and described herein includes a reflective core layer 110, at least one dielectric layer 120 extending on the reflective core layer 110, at least one metal absorption layer 130 extending on the at least one dielectric layer 120, and at least one dielectric outer layer 140 extending on the at least one metal absorption layer 130.

[0034] In some embodiments, reference Figure 1BThe multilayer film 100 includes a reflective core layer 110, a protective layer 150 encapsulating the reflective core layer 110, at least one dielectric layer 120 extending on at least a portion of the protective layer 150, at least one barrier layer 160 extending on the dielectric layer 120, at least one metal absorption layer 130 extending on the at least one barrier layer 160, and at least one dielectric outer layer 140 extending on the at least one metal absorption layer 130.

[0035] refer to Figures 2A-2C and 3 , depict the effectiveness of different types of layers extending over the reflective core layer 110 in achieving a desired hue level in the red region of the visible spectrum as plotted or displayed in Lab color space. Figure 2A A ZnS dielectric layer 120a extending over the reflective core layer 110 is depicted, Figure 2B Depicted is a Si semiconductor absorber layer 120b extending over the reflective core layer 110, Figure 2C A Fe2O3 dielectric absorption layer 120c extending over the reflective core layer 110 is depicted. Figures 2A-2C The reflectivity simulation of each multilayer film shown in FIG. 1 is performed as a function of the different thicknesses of the dielectric layer 120 a, the semiconductor absorption layer 120 b, and the dielectric absorption layer 120 c. The simulation results are plotted on the Lab color space (also called the a*b* color diagram), as shown in FIG. Figure 3 shown. Figure 3 Each data point shown in Figure 2A The dielectric layer of the multilayer film shown in Figure 2B The semiconductor absorption layer of the multilayer film shown in Figure 2C The specific thickness of the dielectric absorber layer of the multilayer film shown in FIG provides chromaticity and hue. Chromaticity can be defined as Hue can be defined as tan -1 (a* / b*). Hue can also be referred to as the angle relative to the positive a* axis for a given data point. Hue values ​​provide a measure of the color an object appears to be (e.g., red, green, blue, yellow, etc.), and chromaticity values ​​provide a measure of the "brightness" of the color. Figure 3 As shown, Figure 2B and 2C Compared with the multilayer films shown, Figure 2A The multilayer film shown has a lower chromaticity. Figures 2A-2C and Figure 3 It is shown that when a high chromaticity color is desired, an absorbing layer (eg, a dielectric absorbing layer) is more preferred than a dielectric layer as the first layer extending over the reflective core layer.

[0036] refer to Figures 4A-4C , which depicts the relationship between chroma and hue and layer thickness. Specifically, Figure 4A Depicted in a graphical manner as Figure 2A Chromaticity and hue as a function of thickness of a ZnS dielectric layer extending on an Al reflective core layer are shown in FIG. Figure 4B Depicted as Figure 2B Chromaticity and hue as a function of thickness of a Si semiconductor absorber layer extending on an Al reflective core layer are shown in FIG. Figure 4C Depicted as Figure 2C Chromaticity and hue as a function of thickness of a Fe2O3 dielectric absorber layer extending on an Al reflective core layer are shown in FIG. Figures 4A-4C The dashed line in corresponds to the desired hue value between 10° and 30° on the Lab color space. Figures 4A-4C It is shown that multilayer films having a dielectric absorber layer extending over a reflective core layer achieve higher chromaticity values ​​in the hue range between 10° and 30°.

[0037] Reference again Figure 1A , a multilayer film 100 reflecting omnidirectional high chromaticity structural color according to an embodiment is shown. The multilayer film 100 includes a reflective core layer 110, a dielectric absorption layer 120 extending on the reflective core layer 110, a metal absorption layer 130 extending on the dielectric absorption layer 120, and a dielectric outer layer 140 extending on the at least one metal absorption layer 130. In an embodiment, the "outer layer" has a free outer surface (i.e., an outer surface that is not in contact with an absorption layer or another dielectric layer that is not part of a protective coating). It should be understood that in an embodiment, two dielectric absorption layers 120, two metal absorption layers 130, and two dielectric outer layers 140 can be located on opposite sides of the reflective core layer 110, so that the reflective core layer 110 is a core layer sandwiched between a pair of dielectric absorption layers 120, a pair of metal absorption layers 130, and a pair of dielectric outer layers 140. Such a multilayer film having a reflective core layer 110 sandwiched between a pair of dielectric absorbing layers 120, a pair of metallic absorbing layers 130, and a pair of dielectric outer layers may be referred to as a seven-layer multilayer film.

[0038] In an embodiment, the reflective core layer 110 may have a thickness between 50 nm and 500 nm, such as between 100 nm and 500 nm, between 150 nm and 500 nm, between 200 nm and 500 nm, between 250 nm and 500 nm, between 300 nm and 500 nm, between 350 nm and 500 nm, between 400 nm and 500 nm, between 450 nm and 500 nm, between 50 nm and 450 nm, such as 10 between 100nm and 400nm, between 150nm and 450nm, between 200nm and 450nm, between 250nm and 450nm, between 300nm and 450nm, between 350nm and 450nm, between 400nm and 450nm, between 50nm and 400nm, for example, between 100nm and 400nm, between 150nm and 400nm, between 200nm and 400nm, between 250nm and 40 ...500nm and 400nm, between 500nm and 400nm, between 500nm and 400nm, between 500nm and 400nm, between 500nm and 400nm, between 50 between 300nm and 400nm, between 350nm and 400nm, between 50nm and 350nm, for example, between 100nm and 350nm, between 150nm and 350nm, between 200nm and 350nm, between 250nm and 350nm, between 300nm and 350nm, between 50nm and 300nm, for example, between 100nm and 300nm, between 150nm and 300nm, between 200nm and Between 300nm, between 250nm and 300nm, between 50nm and 250nm, for example between 100nm and 250nm, between 150nm and 250nm, between 200nm and 250nm, between 50nm and 200nm, for example between 100nm and 200nm, between 150nm and 200nm, between 50nm and 150nm, for example between 100nm and 150nm, or between 50nm and 100nm.

[0039] In an embodiment, the reflective core layer 110 can be made of at least one "gray metal" material, such as Al, Ag, Pt, Sn; at least one "colored metal" material, such as Au, Cu, brass, bronze, TiN, Cr, or a combination thereof.

[0040] According to an embodiment, the at least one dielectric layer 120 may have a thickness between 10 and 150 nm, for example, between 25 nm and 150 nm, between 50 nm and 150 nm, between 75 nm and 150 nm, between 100 nm and 150 nm, between 125 nm and 150 nm, between 10 and 125 nm, between 25 nm and 125 nm, between 50 nm and 125 nm, between 75 nm and 125 nm, between 100 nm and 125 nm, between 10 and 100 nm, between 25 nm and 100 nm, between 50 nm and 100 nm, between 75 nm and 100 nm, between 10 and 75 nm, between 25 nm and 75 nm, between 50 nm and 75 nm, between 10 and 50 nm, between 25 nm and 50 nm, or between 10 and 25 nm.

[0041] The at least one dielectric layer 120 is TiO2 and may be deposited by CVD or atomic layer deposition ALD on the reflective core layer 110. It has been unexpectedly discovered that certain phases of TiO2 provide a dielectric layer 120 that allows for uniform deposition of subsequent layers.

[0042] It has been found that crystalline phase TiO2, such as rutile phase TiO2 and anatase phase TiO2, is deposited as an uneven, jagged layer on a substrate (e.g., a reflective core layer 110 or a protective layer, which is disclosed in more detail below). This uneven, jagged layer of crystalline phase TiO2 makes it difficult to deposit subsequent layers and makes it extremely difficult to subsequently deposit uniform layers. Without being bound by any particular theory, it is believed that the crystal structure of TiO2 makes it difficult or even impossible to deposit a nanometer-scale smooth crystalline phase TiO2 layer, which is required for the multilayer thin film structure of the embodiment. For example Figure 5 5 shows a magnified image of a rutile phase TiO2 dielectric layer 501 deposited on a silicon dioxide protective layer 502 located on a reflective core 503. In an embodiment, the TiO2 layer can be deposited by a wet chemical process. Figure 5 As can be seen, when deposited at the nanoscale (about 200 nm), the rutile phase TiO2 501 has a very uneven, jagged surface. This results in a dielectric layer with a large surface area and makes the deposition of subsequent layers very difficult and time consuming. In addition, as Figure 6As shown, the metal absorber layer 601 deposited by ALD on the rutile phase TiO2 dielectric layer 501 has a non-uniform thickness and surface that exhibits the topography of the rutile phase TiO2 dielectric layer 501. It should be understood that the varying thickness and undulating surface of the metal absorber layer 601 may have a significant effect on the electromagnetic radiation reflected from the multilayer thin film. In addition, the non-uniformity originating from the rutile phase TiO2 dielectric layer 501 propagates to the undulations in the dielectric outer layer 602. Likewise, these undulations in the dielectric outer layer 602 can affect the electromagnetic radiation reflected by the multilayer thin film structure.

[0043] Reference now Figure 7 , a multilayer thin film structure 700 made of an amorphous TiO2 dielectric layer will be described. Figure 7 In the embodiment, SiO2 protective layer 702 is located on Al reflective layer 701. On the protective layer is an amorphous TiO2 dielectric layer 703. Figure 5 and Figure 6 Compared with the rutile phase TiO2 dielectric layer shown in Figure 7 The amorphous TiO2 dielectric layer 703 shown in FIG. 7 has a smooth surface, allowing subsequent layers to be easily and uniformly deposited (i.e., without varying thickness and undulations). However, in embodiments, the amorphous TiO2 dielectric layer can have a relatively high porosity, which can allow some material from the layer to be deposited onto the amorphous TiO2 to penetrate into the amorphous TiO2 dielectric layer. When an optical layer (e.g., a metal absorption layer) is deposited onto the amorphous TiO2 dielectric layer, this penetration can change the optical properties of the multilayer thin film structure. Therefore, in embodiments, as shown in FIG. Figure 7 As shown, before depositing the metal absorption layer 705 on the multilayer thin film structure, a barrier layer 704 having no significant optical properties can be deposited on the amorphous TiO2 dielectric layer to fill the holes. In an embodiment, the barrier layer 704 is made of aluminum oxide (Al2O3) and has a thickness of less than or equal to 10 nm, for example, less than or equal to 8 nm, less than or equal to 6 nm, less than or equal to 4 nm, or less than or equal to 2 nm, and can be deposited on the amorphous TiO2 dielectric layer by ALD. Figure 7 As shown, a uniform and smooth tungsten metal absorption layer 705 is deposited on the Al2O3 barrier layer 704, and a uniform and smooth TiO2 dielectric outer layer 706 is deposited on the metal absorption layer 705. Figure 7 The illustrated multilayer thin film structure 700 has layers with uniform thickness and minimal undulations, which provides uniform reflection of electromagnetic radiation.

[0044] In order to obtain an amorphous TiO2 dielectric layer, the ALD or CVD method used to deposit the TiO2 dielectric layer should be carried out at a temperature and pressure that does not allow TiO2 to crystallize and form a rutile or anatase phase. Without being bound by any particular theory, it is believed that the deposition temperature can help apply the TiO2 amorphous phase. For example, in an embodiment where the TiO2 layer is deposited by CVD, the deposition temperature is less than 500°C, such as less than 475°C, less than 450°C, less than 425°C, or less than 400°C. In an embodiment where the TiO2 layer is deposited by ALD, the deposition temperature is less than 180°C, such as less than 160°C, less than 140°C, or less than 120°C. This application process can provide a dense layer with very little porosity. The surface of these layers is smooth, there is no rough grain formation and the porosity is very small.

[0045] The metallic absorber layer 130 extends between the dielectric layer 120 and the dielectric outer layer 140. The location of the metallic absorber layer 130 is selected to increase absorption of the target wavelength of light. For example, if the multilayer film is configured to absorb electromagnetic radiation having a wavelength less than or equal to 550 nm, but reflect electromagnetic radiation having a wavelength of approximately 650 nm, such as visible light outside the hue between 10° and 30°, the absorber layer is placed at a thickness such that the electric field (|E| 2 ) at 550nm is smaller than at 650nm. Mathematically, this can be expressed as:

[0046] |E 550 | 2 << |E 650 | 2 (1)

[0047] And preferably:

[0048] |E 650 | 2 ≈0(2)

[0049] Figure 8 and the following discussion provides methods for calculating the thickness of a zero or near-zero electric field point at a given wavelength of light according to an embodiment. For the purposes of this specification, the term "near-zero" is defined as |E| 2 ≤10. Figure 8 It shows that in the case of a s " is a multilayer film having a dielectric layer 4 on a substrate layer 2, the dielectric layer 4 having a total thickness "D", an incremental thickness "d" and a refractive index "n". The substrate layer 2 can be a core layer or a reflective core layer of the multilayer film. The incident light strikes the outer surface 5 of the dielectric layer 4 at an angle θ relative to a line 6 perpendicular to the outer surface 5 and is reflected from the outer surface 5 at the same angle θ. The incident light strikes the outer surface 5 of the dielectric layer 4 at an angle θ relative to the line 6 F Transmitted through the outer surface 5 and into the dielectric layer 4, and at an angle θ sThe surface 3 of the substrate layer 2 is illuminated. For a single dielectric layer, θ s＝ θ F , when z = d, energy / electric field (E) can be expressed as E(z). According to Maxwell's equations, the electric field of s polarization can be expressed as: For p polarization: in λ is the desired wavelength to be reflected, α = n s sinθ s , where "s" corresponds to Figure 8 The substrate in is the dielectric constant of the layer as a function of z. Like this: |E(d)| 2 =|u(z) 2 exp(2ikαy)| z＝d (5) For s-polarization, and For p-polarization.

[0050] It should be understood that the electric field variation along the Z direction of the dielectric layer 4 can be estimated by calculating the unknown parameters u(z) and v(z), where it can be shown that: where 'i' is the square root of -1. Using boundary conditions u| z＝0 =1,v| z＝0 =q s , and have the following relationship: q s =n s cosθ s (for s-polarization) (8) q s =n s / cosθ s (for p-polarization) (9) q=n cosθ F (for s-polarization) (10) q=n / cosθ F (for p-polarization) (11) u(z) and v(z) can be expressed as: as well as therefore: For s-polarization and: For p-polarization, where: α=n s sinθ s =nsinθ F (17) as well as

[0051] Therefore, for θ F = 0 or the simple case of normal incidence, And α=0:

[0052] This allows solving for the thickness "d" (i.e., the position or location within the dielectric layer where the electric field is zero). It should be understood that the thickness "d" can be the thickness of the dielectric layer 120 extending over the reflective core layer 110, which provides a zero or near-zero electric field at the interface between the dielectric layer 120 and the metal absorbing layer 130. It should also be understood that the thickness "d" can also be the thickness of the dielectric outer layer 140 extending over the metal absorbing layer 130, which provides a zero or near-zero electric field at the interface between the dielectric outer layer and the metal absorbing layer 130, depending on the thickness "d" at which the electric field is zero or near-zero.

[0053] In an embodiment, at least one metal absorption layer 130 may have a thickness between 5 nm and 20 nm, for example, between 8 nm and 20 nm, between 10 nm and 20 nm, between 12 nm and 20 nm, between 15 nm and 20 nm, between 18 nm and 20 nm, between 5 nm and 18 nm, between 8 nm and 18 nm, between 10 nm and 18 nm, between 12 nm and 18 nm, between 15 nm and 18 nm, between 5 nm and 15 nm, between 8 nm and 15 nm, between 10 nm and 15 nm, between 12 nm and 15 nm, between 5 nm and 12 nm, between 8 nm and 12 nm, between 10 nm and 12 nm, between 5 nm and 10 nm, between 8 nm and 10 nm, or between 5 nm and 8 nm. In an embodiment, the metal absorption layer 130 may be made of at least one material selected from W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide, or a combination thereof. In one or more embodiments, the metal absorber layer 130 is composed of W. In embodiments, ALD is used to deposit the metal absorber layer 130 because ALD allows the material to be uniformly deposited at a desired thickness. Other deposition methods have difficulty depositing uniform layers with a thickness of 20 nm and below.

[0054] In an embodiment, at least one dielectric outer layer 140 may have a thickness greater than 0.1 quarter wavelength (QW) to less than or equal to 4.0 QW, wherein the control wavelength is determined by a target wavelength at peak reflection in the visible wavelengths, for example, between 0.5 QW and 4.0 QW, between 1.0 QW and 4.0 QW, between 1.5 QW and 4.0 QW, between 2.0 QW and 4.0 QW, between 2.5 QW and 4.0 QW, between 3.0 QW and 4.0 QW, or between 3.5 QW and 4.0 QW. In an embodiment, at least one dielectric outer layer 140 may have a thickness from greater than 0.1QW to less than 3.5QW, such as from greater than 0.1QW to less than 3.0QW, from greater than 0.1QW to less than 2.5QW, from greater than 0.1QW to less than 2.0QW, from greater than 0.1QW to less than 1.5QW, from greater than 0.1QW to less than 1.0QW, or from greater than 0.1QW to less than 0.5QW. In some embodiments, at least one dielectric outer layer 140 may have a thickness of 0.5QW to 3.5QW, such as 1.0QW to 3.0QW, or 1.5QW to 2.5QW. In an embodiment, the target wavelength may be about 1050nm. The outer dielectric layer may be made of a dielectric material having a refractive index greater than 1.6, such as ZnS and TiO2 or a combination thereof. In an embodiment, the outer layer may be deposited by CVD or ALD.

[0055] In embodiments, the dielectric outer layer 140 may have a thickness between 5 and 500 nm, such as between 50 nm and 500 nm, between 100 nm and 500 nm, between 150 nm and 500 nm, between 200 nm and 500 nm, between 250 nm and 500 nm, between 300 nm and 500 nm, between 350 nm and 500 nm, between 400 nm and 500 nm, or between 450 nm and 500 nm. In some embodiments, at least one dielectric layer 120 may have a thickness between 5 nm and 450 nm, such as between 5 nm and 400 nm, between 5 nm and 350 nm, between 5 nm and 300 nm, between 5 nm and 250 nm, between 5 nm and 200 nm, between 5 nm and 150 nm, between 5 nm and 100 nm, or between 5 nm and 50 nm. In embodiments, the dielectric outer layer may have a thickness between 50 nm and 450 nm, such as between 100 nm and 400 nm, between 150 nm and 350 nm, or between 200 nm and 300 nm.

[0056] When viewed at an angle of 0° to 45°, embodiments of the multilayer film 100 described above have a color shift in the Lab color space of less than 30°, such as less than 25°, less than 20°, less than 15°, or less than 10°.

[0057] In one or more embodiments, the multilayer film 100 includes a reflective core layer 110 made of Al, a dielectric layer 120 extending on the reflective core layer 110 and deposited by ALD or CVD and made of TiO2, a metal absorption layer 130 extending on the dielectric layer 120 and deposited by ALD and made of W, and a dielectric outer layer 140 extending on the metal absorption layer 130 and deposited by ALD or CVD and made of TiO2.

[0058] In one or more embodiments, the multilayer film 100 includes a reflective core layer 110 made of Al, a dielectric layer 120 made of TiO2 deposited by ALD or CVD and extending on the reflective core layer 110, a metal absorption layer 130 made of W deposited by ALD and extending on the dielectric layer 120, and a dielectric outer layer 140 made of ZnS deposited by ALD or CVD and extending on the metal absorption layer 130.

[0059] Reference again Figure 1B, shows a multilayer film 100 that reflects omnidirectional high chromaticity structural colors according to an embodiment. The multilayer film 100 includes a reflective core layer 110, a protective layer 150 encapsulating the reflective core layer 110, a dielectric layer 120 extending on at least a portion of the protective layer 150, a barrier layer 160 extending on the dielectric layer, a metal absorption layer 130 extending on the barrier layer 160, and a dielectric outer layer 140 extending on at least one metal absorption layer 130. In an embodiment, the "outer layer" has an outer free surface (i.e., an outer surface that is not in contact with an absorption layer or another dielectric layer that is not part of the protective coating). It should be understood that in an embodiment, two dielectric layers 120, two metal absorption layers 130, and two dielectric outer layers 140 can be positioned on opposite sides of the reflective core layer 110, so that the reflective core layer 110 is a core layer encapsulated by the protective layer 150 and sandwiched between a pair of dielectric layers 120, a pair of metal absorption layers 130, and a pair of dielectric outer layers 140. Such a multilayer film having a reflective core layer 110 encapsulated by a protective layer 150 and sandwiched between a pair of dielectric layers 120, a pair of metallic absorbing layers 130, and a pair of dielectric outer layers 140 may be referred to as a nine-layer multilayer film.

[0060] In an embodiment, the reflective core layer 110 may have a thickness between 50 nm and 500 nm, such as between 100 nm and 500 nm, between 150 nm and 500 nm, between 200 nm and 500 nm, between 250 nm and 500 nm, between 300 nm and 500 nm, between 350 nm and 500 nm, between 400 nm and 500 nm, between 450 nm and 500 nm, between 50 nm and 450 nm, such as 10 between 0nm and 450nm, between 150nm and 450nm, between 200nm and 450nm, between 250nm and 450nm, between 300nm and 450nm, between 350nm and 450nm, between 400nm and 450nm, between 50nm and 400nm, for example, between 100nm and 400nm, between 150nm and 400nm, between 200nm and 400nm, between 250nm and 40 ...50nm and 400nm, between 50nm and 400nm, between 50nm and 400nm, between 50nm and 400nm, between 50nm and 400nm, between 50nm and 400nm between 300nm and 400nm, between 350nm and 400nm, between 50nm and 350nm, for example, between 100nm and 350nm, between 150nm and 350nm, between 200nm and 350nm, between 250nm and 350nm, between 300nm and 350nm, between 50nm and 300nm, for example, between 100nm and 300nm, between 150nm and 300nm, between 200nm and Between 300nm, between 250nm and 300nm, between 50nm and 250nm, for example between 100nm and 250nm, between 150nm and 250nm, between 200nm and 250nm, between 50nm and 200nm, for example between 100nm and 200nm, between 150nm and 200nm, between 50nm and 150nm, for example between 100nm and 150nm, or between 50nm and 100nm.

[0061] In an embodiment, the reflective core layer 110 can be made of at least one of "gray metal" materials, such as Al, Ag, Pt, Sn; at least one of "colored metal" materials, such as Au, Cu, brass, bronze, TiN, Cr or a combination thereof.

[0062] In an embodiment, at least one protective layer 150 may have a thickness between 2 nm and 70 nm, for example, between 5 nm and 70 nm, between 10 nm and 70 nm, between 20 nm and 70 nm, between 30 nm and 70 nm, between 40 nm and 70 nm, between 50 nm and 70 nm, between 60 nm and 70 nm, between 2 nm and 60 nm, between 5 nm and 60 nm, between 10 nm and 60 nm, between 20 nm and 60 nm, between 30 nm and 60 nm, between 40 nm and 60 nm, between 50 nm and 60 nm, between 2 nm and 50 nm, between 5 nm and 50 nm, between , 10nm to 50nm, 20nm to 50nm, 30nm to 50nm, 40nm to 50nm, 2nm to 40nm, 5nm to 40nm, 10nm to 40nm, 20nm to 40nm, 30nm to 40nm, 2nm to 30nm, 5nm to 30nm, 10nm to 30nm, 20nm to 30nm, 2nm to 20nm, 5nm to 20nm, 10nm to 20nm, 2nm to 10nm, 5nm to 10nm, or 2nm to 5nm. In an embodiment, the protective layer can be made of SiO2, SnO2, Al2O3, or a combination thereof. In an embodiment, the protective layer 150 can be deposited on the reflective core layer 110 by a wet chemical deposition technique (e.g., a sol-gel deposition technique).

[0063] Without being bound by any particular theory, it is believed that the protective layer 150 is advantageous in embodiments where the dielectric layer 120 extends over the reflective core layer 110 because the process used to deposit the dielectric layer 120 can damage the reflective core layer 110, for example by oxidizing or deforming the reflective core layer 110. The protective layer 150 protects the reflective core layer 110 from damage caused by, for example, strong alkaline / acidic conditions of wet chemical deposition. However, the addition of the protective layer 150 can change the reflectivity of the reflective core layer 110. Therefore, a thin protective layer 150 having a thickness as described above is desired because a thicker protective layer may have an undesirable effect on the reflectivity of the multilayer film. In embodiments, the change in reflectivity caused by the protective layer 150 can be compensated by adding a corresponding metal absorbing layer 130 and an outer layer made of a dielectric material.

[0064] According to an embodiment, the at least one dielectric layer 120 may have a thickness between 10 and 150 nm, for example, between 25 nm and 150 nm, between 50 nm and 150 nm, between 75 nm and 150 nm, between 100 nm and 150 nm, between 125 nm and 150 nm, between 10 and 125 nm, between 25 nm and 125 nm, between 50 nm and 125 nm, between 75 nm and 125 nm, between 100 nm and 125 nm, between 10 and 100 nm, between 25 nm and 100 nm, between 50 nm and 100 nm, between 75 nm and 100 nm, between 10 nm and 75 nm, between 25 nm and 75 nm, between 50 nm and 75 nm, between 10 nm and 50 nm, between 25 nm and 50 nm, or between 10 nm and 25 nm.

[0065] At least one dielectric layer 120 is TiO2 and can be deposited on the reflective core layer 110 by chemical vapor deposition (CVD), atomic layer deposition (ALD), or wet chemical processes. As described above, in embodiments, the TiO2 dielectric layer is amorphous TiO2.

[0066] In embodiments including at least one barrier layer 160, the at least one barrier layer 160 may be made of, for example, Al2O3 and SiO2, and have a thickness of 1 nm to 15 nm, for example, 1 nm to 12 nm, 1 nm to 10 nm, 1 nm to 8 nm, 1 nm to 6 nm, 1 nm to 4 nm, 1 nm to 2 nm, 2 nm to 15 nm, 2 nm to 12 nm, 2 nm to 10 nm, 2 nm to 8 nm, 2 nm to 6 nm, 2 nm to 4 nm, 4 nm to 15 nm, 4 nm to 12 nm, 4 nm to 10 nm, 4 nm to 8 nm, 4 nm to 6 nm, 6 nm to 15 nm, 6 nm to 12 nm, 6 nm to 10 nm, 6 nm to 8 nm, 8 nm to 15 nm, 8 nm to 12 nm, 8 nm to 10 nm, 10 nm to 15 nm, 10 nm to 12 nm, or 12 nm to 15 nm. According to one or more embodiments, the at least one barrier layer 160 is deposited by ALD. In an embodiment, at least one barrier layer 160 is SiO2 and is deposited by a wet chemical process. In an embodiment, at least one barrier layer 160 is Al2O3 and is deposited by CVD.

[0067] In an embodiment, the at least one metallic absorption layer 130 can be positioned so that the electric field of the target wavelength to be reflected is zero or close to zero, as described above. In an embodiment, the at least one metallic absorption layer 130 has a thickness between 5nm and 20nm, for example, between 8nm and 20nm, between 10nm and 20nm, between 12nm and 20nm, between 15nm and 20nm, between 18nm and 20nm, between 5nm and 18nm, between 8nm and 18nm, between 10nm and 18nm, between 12nm and 18nm, between 15nm and 18nm, between 5nm and 15nm, between 8nm and 15nm, between 10nm and 15nm, between 12nm and 15nm, between 5nm and 12nm, between 8nm and 12nm, between 10nm and 12nm, between 5nm and 10nm, between 8nm and 10nm, or between 5nm and 8nm. In an embodiment, the metal absorption layer 130 can be made of at least one material selected from W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide, or a combination thereof. In one or more embodiments, the metal absorption layer 130 is composed of W. In an embodiment, ALD is used to deposit the metal absorption layer 130 because ALD allows the material to be uniformly deposited at a desired thickness. Other deposition methods have difficulty in depositing uniform layers with a thickness of 20 nm and below.

[0068] In an embodiment, at least one dielectric outer layer 140 may have a thickness greater than 0.1 quarter wavelength (QW) to less than or equal to 4.0 QW, wherein the control wavelength is determined by a target wavelength at peak reflection in the visible wavelengths, for example, between 0.5 QW and 4.0 QW, between 1.0 QW and 4.0 QW, between 1.5 QW and 4.0 QW, between 2.0 QW and 4.0 QW, between 2.5 QW and 4.0 QW, between 3.0 QW and 4.0 QW, or between 3.5 QW and 4.0 QW. In an embodiment, at least one dielectric outer layer 140 may have a thickness from greater than 0.1QW to less than 3.5QW, such as from greater than 0.1QW to less than 3.0QW, from greater than 0.1QW to less than 2.5QW, from greater than 0.1QW to less than 2.0QW, from greater than 0.1QW to less than 1.5QW, from greater than 0.1QW to less than 1.0QW, or from greater than 0.1QW to less than 0.5QW. In some embodiments, at least one dielectric outer layer 140 may have a thickness of 0.5QW to 3.5QW, such as 1.0QW to 3.0QW, or 1.5QW to 2.5QW. In an embodiment, the target wavelength may be about 1050nm. The outer dielectric layer may be made of a dielectric material having a refractive index greater than 1.6, such as ZnS and TiO2 or a combination thereof. In an embodiment, the outer layer may be deposited by CVD or ALD.

[0069] In embodiments, the dielectric outer layer 140 may have a thickness between 5 and 500 nm, such as between 50 nm and 500 nm, between 100 nm and 500 nm, between 150 nm and 500 nm, between 200 nm and 500 nm, between 250 nm and 500 nm, between 300 nm and 500 nm, between 350 nm and 500 nm, between 400 nm and 500 nm, or between 450 nm and 500 nm. In some embodiments, at least one dielectric layer 120 may have a thickness between 5 nm and 450 nm, such as between 5 nm and 400 nm, between 5 nm and 350 nm, between 5 nm and 300 nm, between 5 nm and 250 nm, between 5 nm and 200 nm, between 5 nm and 150 nm, between 5 nm and 100 nm, or between 5 nm and 50 nm. In embodiments, the dielectric outer layer may have a thickness between 50 nm and 450 nm, such as between 100 nm and 400 nm, between 150 nm and 350 nm, or between 200 nm and 300 nm.

[0070] When viewed at an angle of 0° to 45°, embodiments of the multilayer film 100 described above have a color shift in the Lab color space of less than 30°, such as less than 25°, less than 20°, less than 15°, or less than 10°.

[0071] In one or more embodiments, the multilayer film 100 includes a reflective core layer 110 made of Al, a protective layer 150 deposited by a wet chemical process and made of SiO2 that encapsulates the reflective core layer 110, a dielectric layer 120 deposited by CVD, ALD or a wet chemical process and made of TiO2 that extends on at least a portion of the protective layer 150, a metal absorption layer 130 deposited by ALD and made of W that extends on the dielectric layer 120, and a dielectric outer layer 140 deposited by CVD or ALD and made of TiO2 that extends on the metal absorption layer 130.

[0072] In one or more embodiments, the multilayer film 100 includes a reflective core layer 110 made of Al, a protective layer 150 deposited by a wet chemical process and made of SiO2 that encapsulates the reflective core layer 110, a dielectric layer 120 deposited by CVD or ALD or a wet chemical process and made of TiO2 that extends on at least a portion of the protective layer 150, a metal absorption layer 130 deposited by ALD and made of W that extends on the dielectric layer 120, and a dielectric outer layer 140 deposited by CVD or ALD and made of ZnS that extends on the metal absorption layer 130.

[0073] In one or more embodiments, the multilayer film 100 includes a reflective core layer 110 made of Al, a protective layer 150 deposited by a wet chemical process and made of SiO2 that encapsulates the reflective core layer 110, a dielectric layer 120 deposited by CVD, ALD or a wet chemical process and made of TiO2 that extends on at least a portion of the protective layer 150, a barrier layer 160 deposited by ALD and made of Al2O3 that extends on the dielectric layer 120, a metal absorption layer 130 deposited by ALD and made of W that extends on the barrier layer 160, and a dielectric outer layer 140 deposited by CVD or ALD and made of TiO2 that extends on the metal absorption layer 130.

[0074] In one or more embodiments, the multilayer film 100 includes a reflective core layer 110 made of Al, a protective layer 150 deposited by a wet chemical process and made of SiO2 that encapsulates the reflective core layer 110, a dielectric layer 120 deposited by CVD, ALD or a wet chemical process and made of TiO2 that extends on at least a portion of the protective layer 150, a barrier layer 160 deposited by ALD and made of Al2O3 that extends on the dielectric layer 120, a metal absorption layer 130 deposited by ALD and made of W that extends on the barrier layer 160, and a dielectric outer layer 140 deposited by CVD or ALD and made of ZnS that extends on the metal absorption layer 130.

[0075] The multilayer film in the embodiments disclosed herein can be used as a pigment (e.g., a paint pigment for a paint for painting an object), or a continuous film applied to an object. When used as a pigment, at least one of a paint binder and a filler can be used and mixed with the pigment to provide a paint showing an omnidirectional high chromaticity red structural color. In addition, other additives can be added to the multilayer film to contribute to the compatibility of the multilayer film in the paint system. Exemplary compatibility enhancing additives include silane surface treatment agents, which coat the outside of the multilayer film and improve the compatibility of the multilayer film in the paint system. Such paint systems or films can be used for any article, including motor vehicles.

[0076] It should be noted that the terms "substantially" and "approximately" may be used herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. Example

[0077] Embodiments will be further illustrated by the following examples. Example 1

[0078] Five simulations were performed using an amorphous TiO2 dielectric layer with a refractive index ranging from 2.2 to 2.3. The thickness of the TiO2 dielectric layer varied in the simulations. Each simulation included an aluminum core, an amorphous TiO2 dielectric layer deposited on the aluminum core, and a 10nm thick tungsten absorber layer deposited on the amorphous TiO2.

[0079] Fig.9A The simulated reflection curve of the amorphous TiO2 layer with a thickness of 30nm is depicted. The target reflection curve is coarse and has a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig.9A As shown, the simulated reflectance curve does not match the target reflectance curve.

[0080] Fig. 9B The simulated reflection curve of the amorphous TiO2 layer with a thickness of 50nm is depicted. The target reflection curve is coarse and has a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig. 9B As shown, the simulated reflectance curve is close to but does not match the target reflectance curve.

[0081] Fig. 9C The simulated reflection curve of the amorphous TiO2 layer with a thickness of 70nm is depicted. The target reflection curve is coarse with a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig. 9C As shown, the simulated reflectance curve matches the target reflectance curve very well.

[0082] Fig.9D The simulated reflection curve when the thickness of the amorphous TiO2 layer is 90nm is depicted. The target reflection curve is coarse and has a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig.9D As shown, the simulated reflectance curve is wider than the target reflectance curve.

[0083] Fig.9E The simulated reflection curves are depicted, where the amorphous TiO2 layer has a thickness of 70 nm and an additional amorphous TiO2 layer with a thickness of 70 nm is deposited on a 10 nm thick tungsten absorption layer. The target reflection curve is coarse with a single peak around 400 nm wavelength, while the simulated curve is thinner. Fig.9E As shown, the simulated reflectance curve matches the target reflectance curve very well. Example 2

[0084] Six simulations were performed using an amorphous TiO2 dielectric layer with a refractive index ranging from 1.8 to 2.0. The thickness of the TiO2 dielectric layer varied in the simulations. Each simulation included an aluminum core, an amorphous TiO2 dielectric layer deposited on the aluminum core, and a 10nm thick tungsten absorber layer deposited on the amorphous TiO2.

[0085] Fig. 10AThe simulated reflection curve of the amorphous TiO2 layer with a thickness of 30nm is depicted. The target reflection curve is coarse and has a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig. 10A As shown, the simulated reflectance curve does not match the target reflectance curve.

[0086] Fig. 10B The simulated reflection curve of the amorphous TiO2 layer with a thickness of 50nm is depicted. The target reflection curve is coarse and has a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig. 10B As shown, the simulated reflectance curve does not match the target reflectance curve.

[0087] Fig. 10C The simulated reflection curve of the amorphous TiO2 layer with a thickness of 70nm is depicted. The target reflection curve is coarse with a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig. 10C As shown, the simulated reflectance curve is close to but does not match the target reflectance curve.

[0088] Fig. 10D The simulated reflection curve when the thickness of the amorphous TiO2 layer is 90nm is depicted. The target reflection curve is coarse and has a single peak near the wavelength of 400nm, while the simulated curve is thinner. Fig. 10D As shown, the simulated reflectance curve matches the target reflectance curve.

[0089] Fig. 10E The simulated reflection curves are depicted, where the amorphous TiO2 layer has a thickness of 70 nm and an additional amorphous TiO2 layer with a thickness of 70 nm is deposited on a 10 nm thick tungsten absorption layer. The target reflection curve is coarse with a single peak around 400 nm wavelength, while the simulated curve is thinner. Fig. 10E As shown, the simulated reflectance curve is close to but does not match the target reflectance curve.

[0090] Fig.10F The simulated reflection curves are depicted, where the amorphous TiO2 layer has a thickness of 90 nm and an additional amorphous TiO2 layer with a thickness of 90 nm is deposited on a 10 nm thick tungsten absorption layer. The target reflection curve is coarse with a single peak around the 400 nm wavelength, while the simulated curve is thinner. Fig.10F As shown, the simulated reflectance curve matches the target reflectance curve very well.

[0091] It will be apparent to those skilled in the art that various modifications and variations may be made to the embodiments described herein without departing from the spirit and scope of the subject matter claimed. Therefore, this specification is intended to cover modifications and variations of the various embodiments described herein, as long as these modifications and variations fall within the scope of the appended claims and their equivalents.

Claims

1. A multilayer film reflecting omnidirectional structural color, comprising: Reflective core; An amorphous TiO2 dielectric layer extending over the reflective core layer; A metal absorber layer extending on the amorphous TiO2 dielectric layer; as well as A dielectric outer layer extending over the metallic absorbing layer, wherein the multilayer film reflects a single narrowband of visible light when exposed to broadband electromagnetic radiation, the single narrowband of visible light comprising: When the multilayer film is exposed to broadband electromagnetic radiation and viewed at an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer film, the color shift of a single narrow band of visible light measured in Lab color space is less than 30°.

2. The multilayer film of claim 1, wherein the reflective core layer is formed of Al, Ag, Pt, Sn, Au, Cu, brass, bronze, TiN, Cr, or a combination thereof.

3. The multilayer film of claim 1, wherein the thickness of the reflective core layer is between 50 nm and 500 nm.

4. The multilayer film of claim 1, wherein the thickness of the amorphous TiO2 dielectric layer is between 10 nm and 150 nm.

5. The multilayer film of claim 1, wherein the metal absorption layer is formed of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide or a combination thereof.

6. The multilayer film of claim 1, wherein the thickness of the metal absorption layer is between 5 nm and 20 nm.

7. The multilayer film of claim 1, wherein the dielectric outer layer is formed of ZnS, TiO2, and combinations thereof.

8. The multilayer film of claim 1, wherein the dielectric outer layer has a thickness greater than 0.1 quarter wavelength (QW) to less than or equal to 4.0 QW, wherein the control wavelength is determined by a target wavelength at peak reflection in the visible wavelength.

9. The multilayer film of claim 1, wherein the thickness of the dielectric outer layer is between 5 nm and 500 nm.

10. The multilayer film according to claim 1, wherein The reflective core layer is formed of Al, The metal absorption layer is formed of W, and The dielectric outer layer is formed of ZnS or TiO2.

11. A multilayer film reflecting omnidirectional structural color, comprising: Reflective core; A protective layer encapsulating a reflective core layer; an amorphous TiO2 dielectric layer extending over at least a portion of the protective layer; A barrier layer extending over the amorphous TiO2 dielectric layer; a metallic absorber layer extending over the barrier layer; as well as A dielectric outer layer extends over the metallic absorbing layer, wherein When exposed to broadband electromagnetic radiation, the multilayer film reflects a single narrow band of visible light comprising: When the multilayer film is exposed to broadband electromagnetic radiation and viewed at an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer film, the color shift of a single narrow band of visible light measured in Lab color space is less than 30°.

12. The multilayer film of claim 11, wherein the reflective core layer is formed of Al, Ag, Pt, Sn, Au, Cu, brass, bronze, TiN, Cr, or a combination thereof.

13. The multilayer film of claim 11, wherein the thickness of the reflective core layer is between 50 nm and 500 nm.

14. The multilayer thin film according to claim 11, wherein the protective layer is formed of SiO2, SnO2, Al2O3, or a combination thereof.

15. The multilayer film of claim 11, wherein the protective layer has a thickness between 2 nm and 70 nm.

16. The multilayer film of claim 11, wherein the thickness of the amorphous TiO2 dielectric layer is between 10 nm and 150 nm.

17. The multilayer film of claim 11, wherein the metal absorption layer is formed of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide, amorphous silicon or a combination thereof.

18. The multilayer film of claim 11, wherein the metal absorption layer has a thickness of 5 nm to 20 nm.

19. The multilayer film of claim 11, wherein the dielectric outer layer is formed of ZnS, TiO2, and combinations thereof.

20. The multilayer film of claim 11, wherein the dielectric outer layer has a thickness greater than 0.1 quarter wavelength (QW) to less than or equal to 4.0 QW, wherein the control wavelength is determined by a target wavelength at peak reflection in the visible wavelengths.

21. The multilayer film of claim 11, wherein the thickness of the dielectric outer layer is between 5 nm and 500 nm.

22. The multilayer film of claim 11, wherein the barrier layer is formed of Al2O3.

23. The multilayer film of claim 11, wherein the barrier layer has a thickness between 1 nm and 15 nm.

24. The multilayer film of claim 11, wherein The reflective core layer is formed of Al, The protective layer is formed of SiO2. The metal absorption layer is formed by W, The barrier layer is formed of Al2O3, and The dielectric outer layer is formed of ZnS or TiO2.

25. A method of forming the multilayer film of claim 1, the method comprising: Depositing an amorphous TiO2 dielectric layer onto the reflective core layer by CVD or ALD; Depositing a metal absorber layer onto the amorphous TiO2 dielectric layer by ALD; and The dielectric outer layer is deposited onto the metallic absorber layer by CVD or ALD.

26. A method of forming the multilayer film of claim 11, the method comprising: depositing a protective layer onto the reflective core layer by a wet chemical process; Depositing an amorphous TiO2 dielectric layer onto the protective layer by CVD, ALD or wet chemical process; Depositing a barrier layer onto the amorphous TiO2 dielectric layer by ALD; depositing a metal absorber layer onto the barrier layer by ALD; as well as The dielectric outer layer is deposited onto the metallic absorber layer by CVD or ALD.

27. A paint system comprising: Adhesives; as well as The multilayer film of claim 1.

28. A motor vehicle comprising the paint system of claim 27.

29. A paint system comprising: Adhesives; as well as The multilayer film of claim 11.

30. A motor vehicle comprising the paint system of claim 29.

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