Structural color multilayer structure with barrier layer

Abstract

A color reflecting multilayer structure has a core layer and a conformal dielectric layer encapsulating the core layer. A conformal barrier layer encapsulates the conformal dielectric layer, and a conformal absorber layer encapsulates the conformal barrier layer.

Description

Cross - Reference to Related Applications

[0001] This application claims the benefit of priority of U.S. Patent Application No. 18 / 116,600, filed Mar. 2, 2023, which claims the benefit of priority of U.S. Provisional Application No. 63 / 404,413, filed Sep. 7, 2022, the content of which is hereby incorporated by reference in its entirety. Technical Field

[0002] This application relates to multi - layer structures and, in particular, to multi - layer structures including a multi - layer structure having a metal and a metal oxide above a substrate for optical applications. At least one of the metal and the metal oxide is deposited by atomic layer deposition (ALD), and a barrier layer is located between each adjacent metal and / or metal oxide layer. Background Art

[0003] Pigments made of multi - layer structures are known. In addition, pigments that exhibit or provide high - chroma structural color are also known. However, it may be difficult to form multi - layer structures from certain materials because the deposition techniques for depositing various materials may have a negative impact on previously deposited materials. In addition, certain deposition techniques may be expensive and time - consuming, making it difficult to achieve a commercially viable multi - layer structure.

[0004] It should be understood that the color produced by a multi - layer structure depends on the materials used for each layer, the position of the materials within the multi - layer structure, and the properties (e.g., thickness) of each layer. Thus, small changes in the multi - layer structure design can have a significant impact on the color produced by the multi - layer structure. However, conventional deposition techniques are not always effective for depositing the desired layers within the multi - layer structure to achieve an optimal combination of the multi - layer structure. Summary of the Invention

[0005] According to an embodiment, a multi - layer structure that reflects color includes: a core layer; a conformal dielectric layer encapsulating the core layer; a conformal barrier layer encapsulating the conformal dielectric layer; and a conformal absorber layer encapsulating the conformal barrier layer.

[0006] According to an embodiment, the multi - layer structure further includes: a second conformal barrier layer encapsulating the conformal absorber layer; and a second conformal dielectric layer encapsulating the second conformal barrier layer.

[0007] According to an embodiment, a method for manufacturing a multi - layer structure includes: depositing the conformal dielectric layer on the core layer by CVD or ALD; depositing the conformal barrier layer on the conformal dielectric layer by ALD; and depositing the conformal absorber layer on the conformal dielectric layer by ALD.

[0008] Additional features and advantages will be set forth in the following detailed description, and in part will be apparent to those of ordinary skill in the art from the description or may be learned by practice of the embodiments described herein, which include the following detailed description, the claims, and the drawings.

[0009] 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 characteristics of the claimed subject matter. The drawings are included to provide a further understanding of the various embodiments, and the drawings are incorporated in and constitute a part of this specification. The drawings illustrate the various embodiments described herein and, together with the description, serve to explain the principles and operations of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A multilayer structure in accordance with embodiments disclosed and described herein is depicted graphically;

[0011] Figure 2A A multilayer structure having a dielectric layer extending over a reflective core layer used in the design of a multilayer structure is depicted;

[0012] Figure 2B A multilayer structure having an absorber layer extending over a reflective core layer used in the design of a multilayer structure is depicted;

[0013] Figure 2C A multilayer structure having a dielectric layer extending over a reflective core layer used in the design of a multilayer structure in accordance with one or more embodiments shown and described herein is depicted;

[0014] Figure 3 Depicted is Figures 2A - 2C the reflectance characteristics of the depicted multilayer structure in the Lab color space;

[0015] Figure 4A Depicted graphically is Figure 2A the variation of the chromaticity and hue values of the depicted multilayer structure with the thickness of the dielectric layer;

[0016] Figure 4B Depicted graphically is Figure 2B the variation of the chromaticity and hue values of the depicted multilayer structure with the thickness of the semiconductor absorber layer;

[0017] Figure 4C Depicted graphically is Figure 2C the variation of the chromaticity and hue values of the depicted multilayer structure with the thickness of the dielectric layer;

[0018] Figure 5depicts a multilayer structure having a dielectric layer extending over a base layer and exposed to electromagnetic radiation at an angle θ with respect to the normal direction of the outer surface of the dielectric layer;

[0019] Figure 6A is a transmission electron microscope (TEM) image of a multilayer structure having a protective layer and a barrier layer according to the embodiments disclosed and described herein;

[0020] Figure 6B is a further magnified TEM image of a multilayer structure having a protective layer and a barrier layer according to the embodiments disclosed and described herein;

[0021] Figure 6C is a TEM image of a multilayer structure having a protective layer and a barrier layer according to the embodiments disclosed and described herein, wherein the element aluminum is highlighted;

[0022] Figure 6D is a TEM image of a multilayer structure having a protective layer and a barrier layer according to the embodiments disclosed and described herein, wherein the element oxygen is highlighted;

[0023] Figure 6E is a TEM image of a multilayer structure having a protective layer and a barrier layer according to the embodiments disclosed and described herein, wherein the element tungsten is highlighted;

[0024] Figure 6F is a TEM image of a multilayer structure having a protective layer and a barrier layer according to the embodiments disclosed and described herein, wherein the element titanium is highlighted;

[0025] Figure 7A is a TEM image of a multilayer structure without a barrier layer;

[0026] Figure 7B is a further magnified TEM image of a multilayer structure without a barrier layer;

[0027] Figure 7C is a TEM image of a multilayer structure without a barrier layer, wherein the element aluminum is highlighted;

[0028] Figure 7D is a TEM image of a multilayer structure without a barrier layer, wherein the element oxygen is highlighted;

[0029] Figure 7E is a TEM image of a multilayer structure without a barrier layer, wherein the element tungsten is highlighted; and

[0030] Figure 7F is a TEM image of a multilayer structure without a barrier layer, wherein the element titanium is highlighted. Detailed Description

[0031] Fabricating a multi-layer structure can be a complex and expensive process, in part because of the very strict control required over layer thickness. The deposition methods used to deposit the layers can vary in complexity and cost depending on the material that makes up a given layer and the desired thickness of that layer.

[0032] In addition, depositing layers directly on a core layer such as an aluminum (Al) reflective core layer by cheaper wet chemical methods can be challenging because these methods require highly acidic or alkaline conditions. Additionally, there are challenges in depositing precisely controlled ultra-thin absorber layers other than by vacuum coating methods. For example, ALD can deposit thin layers precisely, but ALD is expensive and time-consuming. In particular, the conventionally used ALD methods are low-yield and too expensive for manufacturing on a commercial scale. Moreover, when attempting to increase the yield, it has been noted that various metal and / or metal oxide layers overlap each other and form mixed layers, which can have an impact on the optical properties of the multi-layer structure.

[0033] Embodiments of the multi-layer structures described herein can be used to reflect visible light wavelengths omnidirectionally within an incident angle or viewing angle range (such as a hue between 0° and 120°). It will be understood that the terms "electromagnetic wave", "electromagnetic radiation", and "light" as used herein can be interchangeably substituted to refer to light of various wavelengths incident on the multi-layer structure, and such light can have wavelengths in the ultraviolet (UV), infrared (IR), and visible portions of the electromagnetic spectrum.

[0034] As used herein, a "core layer" refers to both a reflective core layer and a non-reflective core layer, and the "core layer" can have any shape, including but not limited to a sheet, spherical, oval, etc. As used herein, an "absorber layer" includes both a metal absorber layer and a non-metal absorber layer.

[0035] Now referring to Figure 1 , a multi-layer structure 100 according to the embodiments disclosed and described herein includes a core layer 110, a first conformal protective layer 111 encapsulating the core layer 110, a conformal dielectric layer 120 encapsulating the first conformal protective layer 111, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, a conformal absorber layer 130 encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 encapsulating the conformal absorber layer 130, a second conformal dielectric layer 140 encapsulating the second conformal barrier layer 131, and a conformal outer layer 141 encapsulating the second conformal dielectric layer 140.

[0036] In one or more embodiments, the multi-layer structure 100 can include more than Figure 1Layers with fewer layers as depicted. For example, in an embodiment, the multilayer structure 100 includes a core layer 110, a first conformal protective layer 111 encapsulating the core layer 110, a conformal dielectric layer 120 encapsulating the first conformal protective layer 111, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, a conformal absorber layer 130 encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 encapsulating the conformal absorber layer 130, and a second conformal dielectric layer 140 encapsulating the second conformal barrier layer 131.

[0037] In one or more embodiments, the multilayer structure 100 includes a core layer 110, a conformal dielectric layer 120 encapsulating the core layer 110, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, a conformal absorber layer 130 encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 encapsulating the conformal absorber layer 130, and a second conformal dielectric layer 140 encapsulating the second conformal barrier layer 131. An optional conformal outer layer 141 may encapsulate the second conformal dielectric layer 140.

[0038] In an embodiment, the multilayer structure 100 includes a core layer 110, a conformal dielectric layer 120 encapsulating the core layer 110, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, and a conformal absorber layer 130 encapsulating the conformal barrier layer 121. A protective layer may optionally encapsulate the conformal absorber layer.

[0039] In one or more embodiments, the multilayer structure 100 includes a core layer 110, a first conformal protective layer 111 encapsulating the core layer 110, a conformal dielectric layer 120 encapsulating the first conformal protective layer 111, a conformal barrier layer 121 encapsulating the conformal dielectric layer 120, and a conformal absorber layer 130 encapsulating the conformal barrier layer 121. A second conformal barrier layer 131 may optionally encapsulate the conformal absorber layer 130.

[0040] Referring to Figures 2A - 2C and Figure 3 , the effectiveness of different types of layers extending over the reflective core layer 110 in obtaining a desired hue level in the red region of the visible spectrum when plotted or shown in the Lab color space is depicted. Figure 2A A ZnS dielectric layer 120a extending over the reflective core layer 110 is depicted, Figure 2B a Si semiconductor absorber layer 120b extending over the reflective core layer 110 is depicted, and Figure 2C an Fe2O3 absorber layer 120c extending over the reflective core layer 110 is depicted. Depending on the different thicknesses of the dielectric layer 120a, the semiconductor absorber layer 120b, and the absorber layer 120c, Figures 2A - 2C simulations of the reflectivity of each of the multilayer structures shown are performed. The results of this simulation are plotted in the Lab color space, also known as the a*b* color chart, as Figure 3as shown Figure 3 Each data point shown in Figure 2A provides the chroma and hue for a specific thickness of the dielectric layer of the multilayer structure depicted in Figure 2B the semiconductor absorber layer of the multilayer structure depicted in Figure 2C or the absorber layer of the multilayer structure depicted in The chroma can be defined as -1 (a* / b*). The hue can also be defined as tan (a* / b*). The hue can also be referred to as the angle with respect to the positive a* axis for a given data point. The hue value provides a measure of the color (e.g., red, green, blue, yellow, etc.) exhibited by an object, while the chroma value provides a measure of the "brightness" of the color. As Figure 3 shown, compared to the multilayer structure shown in Figure 2B and 2C the multilayer structure shown in Figure 2A provides a low chroma. Thus Figures 2A - 2C and Figure 3 confirm that when a color with a high chroma is desired, the absorber layer (e.g., the absorber layer) is preferred over the dielectric layer as the first layer extending over the reflective core layer. It should be understood that Figure 3 the Lab color space analysis shown in

[0041] is for illustrative purposes, and the multilayer structures according to the embodiments disclosed and described herein can have different Lab color space values. For example, in an embodiment, the multilayer structure can exhibit blue, green, yellow, or other colors in the Lab color space.

[0041] Referring to Figures 4A - 4C chroma and hue are depicted as varying with layer thickness. Specifically Figure 4A graphically depicts the variation of chroma and hue with Figure 2A the thickness of the ZnS dielectric layer extending over the Al reflective core layer shown in Figure 4B depicts the variation of chroma and hue with Figure 2B the thickness of the Si semiconductor absorber layer extending over the Al reflective core layer shown in Figure 4C depicts the variation of chroma and hue with Figure 2C the thickness of the Fe2O3 absorber layer extending over the Al reflective core layer shown in Figures 4A - 4C The dashed line in Figures 4A - 4C corresponds to the desired hue values between 10° and 30° on the Lab color space. Figure 4A shows that for a multilayer structure having an absorber layer extending over the reflective core layer, higher chroma values are achieved within the hue range between 10° and 30°. Again, it should be understood that Figure 4AThe hues and chromaticities shown in –4C are for illustrative purposes, and the multilayer structures according to the embodiments disclosed and described herein may have different hue and chromaticity values.

[0042] Referring again to Figure 1 , the multilayer structure 100 includes a core layer 110, a first conformal protective layer 111 that encapsulates the core layer 110, a conformal dielectric layer 120 that encapsulates the first conformal protective layer 111, a first conformal barrier layer 121 that encapsulates the conformal dielectric layer 120, a conformal absorber layer 130 that encapsulates the first conformal barrier layer 121, a second conformal barrier layer 131 that encapsulates the conformal absorber layer 130, a second conformal dielectric layer 140 that encapsulates the second conformal barrier layer 131, and an optional conformal outer layer 141 that encapsulates the second conformal dielectric layer 140. In an embodiment, the “outer layer” has an external free surface (i.e., an outer surface that does not contact an absorber layer or another dielectric layer that is not part of the protective coating). As Figure 1 shown, embodiments of the multilayer structures disclosed and described herein include a conformal dielectric layer 120 and a conformal absorber layer 130. As used herein, “conformal” is used to indicate that the layer conforms to the size and shape of the layer onto which it is deposited and encapsulates (i.e., is present on all sides) the layer onto which it is deposited and conforms to the contour of the layer onto which it is deposited. Although Figure 1 a rectangular structure is shown, this is for illustrative purposes only, and the multilayer structure will generally have an asymmetric and non-uniform shape. In an embodiment, the multilayer structure may be spherical or oval. It should be understood that the embodiments may also include a multilayer structure having a conformal absorber that encapsulates the core layer and a conformal dielectric layer that encapsulates the conformal absorber layer.

[0043] In an embodiment, the core layer 110 may have a thickness greater than or equal to 20 nm and less than or equal to 100 μm, such as greater than or equal to 50 nm and less than or equal to 80 μm, greater than or equal to 75 nm and less than or equal to 60 μm, greater than or equal to 100 nm and less than or equal to 40 μm, greater than or equal to 125 nm and less than or equal to 20 μm, or greater than or equal to 150 nm and less than or equal to 1 μm. In one or more embodiments, the core layer 110 may have a thickness between 50 nm and 10 μm, such as between 100 nm and 10 μm, between 250 nm and 10 μm, between 500 nm and 10 μm, between 750 nm and 10 μm, between 1 μm and 10 μm, between 2 μm and 10 μm, between 5 μm and 10 μm, between 8 μm and 10 μm, between 50 nm and 8 μm, between 100 nm and 8 μm, between 250 nm and 8 μm, between 500 nm and 8 μm, between 750 nm and 8 μm, between 1 μm and 8 μm, between 2 μm and 8 μm, between 5 μm and 8 μm, between 50 nm and 5 μm, between 100 nm and 5 μm, between 250 nm and 5 μm, between 500 nm and 5 μm, between 750 nm and 5 μm, between 1 μm and 5 μm, between 2 μm and 5 μm, between 50 nm and 2 μm, between 100 nm and 2 μm, between 250 nm and 2 μm, between 500 nm and 2 μm, between 750 nm and 2 μm, between 1 μm and 2 μm, between 50 nm and 1 μm, between 100 nm and 1 μm, between 250 nm and 1 μm, between 500 nm and 1 μm, between 750 nm and 1 μm, between 50 nm and 750 nm, between 100 nm and 750 nm, between 250 nm and 750 nm, between 500 nm and 750 nm, between 50 nm and 500 nm, between 100 nm and 500 nm, between 250 nm and 500 nm, between 50 nm and 250 nm, between 100 nm and 250 nm, or between 50 nm and 100 nm.

[0044] In an embodiment, the core layer 110 may be made of at least one of the following: at least one of "grey metal" materials, such as Al, Ag, Pt, Sn; at least one of "coloured metal" materials, such as Au, Cu, brass, bronze, TiN, Cr, stainless steel, or a combination thereof. In one or more embodiments, the core layer 110 may be made of an oxide, such as aluminium oxide (Al2O3), silicon dioxide (SiO2), bismuth oxychloride, or a glass material. As described above, the core layer 110 may have a plate-like shape, or may be spherical or oval.

[0045] In one or more embodiments, the first conformal protective layer 111 has a thickness less than or equal to 50 nm and greater than or equal to 5 nm, such as less than or equal to 40 nm and greater than or equal to 5 nm, less than or equal to 30 nm and greater than or equal to 5 nm, less than or equal to 20 nm and greater than or equal to 5 nm, less than or equal to 10 nm and greater than or equal to 5 nm, less than or equal to 50 nm and greater than or equal to 10 nm, less than or equal to 40 nm and greater than or equal to 10 nm, less than or equal to 30 nm and greater than or equal to 10 nm, less than or equal to 20 nm and greater than or equal to 10 nm, less than or equal to 50 nm and greater than or equal to 20 nm, less than or equal to 40 nm and greater than or equal to 20 nm, less than or equal to 30 nm and greater than or equal to 20 nm, less than or equal to 50 nm and greater than or equal to 30 nm, less than or equal to 40 nm and greater than or equal to 30 nm, or less than or equal to 50 nm and greater than or equal to 40 nm.

[0046] In an embodiment, the first conformal protective layer 111 can be formed from a chromate coating, a phosphate coating, an oxide coating (such as SiO2), and can be applied to the core layer 110 by chemical vapor deposition (CVD), physical vapor deposition (PVD), wet chemical methods, or ALD.

[0047] According to one or more embodiments, the conformal dielectric layer 120 has a thickness greater than or equal to 5 nm and less than or equal to 500 nm, such as greater than or equal to 10 nm and less than or equal to 475 nm, greater than or equal to 10 nm and less than or equal to 450 nm, greater than or equal to 10 nm and less than or equal to 425 nm, greater than or equal to 10 nm and less than or equal to 400 nm, greater than or equal to 10 nm and less than or equal to 375 nm, greater than or equal to 10 nm and less than or equal to 350 nm, greater than or equal to 10 nm and less than or equal to 325 nm, or greater than or equal to 10 nm and less than or equal to 300 nm. According to an embodiment, the conformal dielectric layer 120 may have a thickness between 5 nm and 300 nm, such as between 10 nm and 300 nm, between 15 nm and 300 nm, between 25 nm and 300 nm, between 50 nm and 300 nm, between 75 nm and 300 nm, between 100 nm and 300 nm, between 125 nm and 300 nm, between 150 nm and 300 nm, between 175 nm and 300 nm, between 200 nm and 300 nm, between 225 nm and 300 nm, between 250 nm and 300 nm, between 275 nm and 300 nm, between 5 nm and 275 nm, between 10 nm and 275 nm, between 15 nm and 275 nm, between 25 nm and 275 nm, between 50 nm and 275 nm, between 75 nm and 275 nm, between 100 nm and 275 nm, between 125 nm and 275 nm, between 150 nm and 275 nm, between 175 nm and 275 nm, between 200 nm and 275 nm, between 225 nm and 275 nm, between 250 nm and 275 nm, between 5 nm and 250 nm, between 10 nm and 250 nm, between 15 nm and 250 nm, between 25 nm and 250 nm, between 50 nm and 250 nm, between 75 nm and 250 nm, between 100 nm and 250 nm, between 125 nm and 250 nm, between 150 nm and 250 nm, between 175 nm and 250 nm, between 200 nm and 250 nm, between 225 nm and 250 nm, between 5 nm and 225 nm, between 10 nm and 225 nm, between 15 nm and 225 nm, between 25 nm and 225 nm, between 50 nm and 225 nm, between 75 nm and 225 nm, between 100 nm and 225 nm, between 125 nm and 225 nm, between 150 nm and 225 nm, between 175 nm and 225 nm, between 200 nm and 225 nm, between 5 nm and 200 nm, between 10 nm and 200 nm,Between 15 nm and 200 nm, between 25 nm and 200 nm, between 50 nm and 200 nm, between 75 nm and 200 nm, between 100 nm and 200 nm, between 125 nm and 200 nm, between 150 nm and 200 nm, between 175 nm and 200 nm, between 5 nm and 175 nm, between 10 nm and 175 nm, between 15 nm and 175 nm, between 25 nm and 175 nm, between 50 nm and 175 nm, between 75 nm and 175 nm, between 100 nm and 175 nm, between 125 nm and 175 nm, between 150 nm and 175 nm, between 5 nm and 150 nm, between 10 nm and 150 nm, between 15 nm and 150 nm, 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 5 nm and 100 nm, between 10 nm and 100 nm, between 15 nm and 100 nm, between 25 nm and 100 nm, between 50 nm and 100 nm, between 75 nm and 100 nm, between 5 nm and 75 nm, between 10 nm and 75 nm, between 15 nm and 75 nm, between 25 nm and 75 nm, between 50 nm and 75 nm, between 5 nm and 50 nm, between 10 nm and 50 nm, between 15 nm and 50 nm, between 25 nm and 50 nm, between 5 nm and 25 nm, between 10 nm and 25 nm, between 15 nm and 25 nm, between 5 nm and 15 nm, between 10 nm and 15 nm, or between 5 nm and 10 nm.,

[0048] In an embodiment, the first conformal dielectric layer 120 is a high refractive index material such as TiO2 (including anatase, rutile or amorphous TiO2 and mixtures thereof), ZnS, ZrO2, HfO2, Fe3O4 or AlAs. In one or more embodiments, the conformal dielectric layer 120 may be made of a high refractive index absorptive dielectric material such as Fe2O3, PbS, GaAs or InAs. In an embodiment, the conformal dielectric layer may be made of a low refractive index material such as SiO2, MgF2, KBr, ZnO or Al2O3. In an embodiment, the conformal dielectric layer 120 may be deposited by CVD, PVD, wet chemical methods or ALD to encapsulate the core layer 110.

[0049] In an embodiment, the first conformal barrier layer 121 has a thickness less than or equal to 50 nm, such as less than or equal to 45 nm, less than or equal to 40 nm, less than or equal to 35 nm, less than or equal to 30 nm, less than or equal to 25 nm, less than or equal to 20 nm, less than or equal to 15 nm, less than or equal to 10 nm, less than or equal to 5 nm, or less than or equal to 2 nm. According to an embodiment, the barrier layer has a thickness greater than or equal to 1 nm and less than or equal to 50 nm, such as greater than or equal to 1 nm and less than or equal to 45 nm, greater than or equal to 1 nm and less than or equal to 40 nm, greater than or equal to 1 nm and less than or equal to 35 nm, greater than or equal to 1 nm and less than or equal to 30 nm, or greater than or equal to 1 nm and less than or equal to 25 nm. In one or more embodiments, the barrier layer has a thickness greater than or equal to 1 nm and less than or equal to 20 nm, such as greater than or equal to 1 nm and less than or equal to 15 nm, greater than or equal to 1 nm and less than or equal to 10 nm, greater than or equal to 1 nm and less than or equal to 5 nm, greater than or equal to 1 nm and less than or equal to 2 nm, greater than or equal to 2 nm and less than or equal to 20 nm, greater than or equal to 2 nm and less than or equal to 15 nm, greater than or equal to 2 nm and less than or equal to 10 nm, greater than or equal to 2 nm and less than or equal to 5 nm, greater than or equal to 5 nm and less than or equal to 20 nm, greater than or equal to 5 nm and less than or equal to 15 nm, greater than or equal to 5 nm and less than or equal to 10 nm, greater than or equal to 10 nm and less than or equal to 20 nm, greater than or equal to 10 nm and less than or equal to 20 nm, greater than or equal to 15 nm and less than or equal to 20 nm, or greater than or equal to 15 nm and less than or equal to 20 nm.

[0050] In an embodiment, the first conformal barrier layer 121 may be formed of A l2 O3, SiO2, MgF2, KBr, or ZnO and may be applied to the first conformal dielectric layer 120 by ALD.

[0051] The conformal absorber layer 130 encapsulates the first conformal barrier layer 121. The position of the conformal absorber layer 130 is selected to increase the absorption of the target optical wavelength. For example, if the multilayer structure is configured to absorb electromagnetic radiation having a wavelength less than or equal to 550 nm but reflect electromagnetic radiation having a wavelength of about 650 nm, such as visible light outside the hue of 10° to 30°, then the absorber layer is placed at a thickness where the electric field (|E| 2 ) at a wavelength of 550 nm is less than that at a wavelength of 650 nm. Mathematically, this can be expressed as: E 550 | 2 <<|E 650 |2 (1) And preferably: |E 650 | 2 ≈0 (2)

[0052] Figure 5 And the following discussion provides a method for calculating the thickness of a zero or near-zero electric field point at a given optical wavelength according to an embodiment. For the purposes of this specification, the term "near zero" is defined as |E| 2 ≤10. Figure 5 A multilayer structure having a dielectric layer 4 on a base layer 2 is shown, the dielectric layer 4 having a total thickness "D", an incremental thickness "d", and a refractive index "n", and the base layer 2 having a refractive index of "n s ". The base layer 2 can be the core layer or the reflective core layer of the multilayer structure. Incident light strikes the outer surface 5 of the dielectric layer 4 at an angle θ with respect to line 6 (which is perpendicular to the outer surface 5) and is reflected from the outer surface 5 at the same angle θ. The incident light transmits through the outer surface 5 at an angle θ F and enters the dielectric layer 4, and strikes the surface 3 of the base layer 2 at an angle θ s . For a single dielectric layer, θ s = θ F , and when z = d, the energy / electric field (E) can be expressed as E(z). From Maxwell's equations, for s polarization, the electric field can be expressed as: And for p polarization, it can be expressed as: Where λ is the desired wavelength to be reflected, α = n s sinθ s , where "s" corresponds to the substrate in FIG. 7, and is the permittivity of the layer as a function of z. Therefore: |E(d)| 2 = |u(z)| 2 exp(2ikαy)| z＝d (5) For s polarization, and For p polarization.

[0053] It should be understood that the variation of the electric field 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 the boundary conditions u| z＝0 = 1, v|z＝0 = q s , and the following relationship: q s = n s cos θ 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: And Therefore: For s-polarization, there is And: For p-polarization, where: α = n s sinθ s = n sinθ F (17) And Therefore, for θ F = 0 or normal incidence, and the simple case where α = 0: This allows the thickness "d" to be solved (i.e., the position or site where the electric field in the dielectric layer is zero). It should be understood that the thickness "d" can be the thickness of the first conformal dielectric layer 120, the first conformal barrier layer 121, and the first conformal protective layer 111 that encapsulate the core layer 110 and provide zero or near-zero electric field at the interface between the first conformal dielectric layer 120 and the conformal absorber layer 130. It should also be understood that the thickness "d" can also be the thickness of the second conformal dielectric layer 140 of the encapsulating second conformal barrier layer 131 that provides zero or near-zero electric field at the interface between the dielectric outer layer and the conformal absorber layer 130, depending on the thickness "d" where the electric field is zero or near-zero.

[0054] In an embodiment, the conformal absorber layer has a thickness greater than or equal to 2 nm and less than or equal to 50 nm, such as greater than or equal to 2 nm and less than or equal to 45 nm, greater than or equal to 2 nm and less than or equal to 40 nm, greater than or equal to 2 nm and less than or equal to 35 nm, greater than or equal to 2 nm and less than or equal to 30 nm, or greater than or equal to 2 nm and less than or equal to 25 nm. In an embodiment, the conformal absorber layer 130 can have a thickness between 2 nm and 20 nm, such as between 5 nm and 20 nm, 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 2 nm and 18 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 2 nm and 15 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 2 nm and 12 nm, between 5 nm and 12 nm, between 8 nm and 12 nm, between 10 nm and 12 nm, between 2 nm and 10 nm, between 5 nm and 10 nm, between 8 nm and 10 nm, between 2 nm and 8 nm, between 5 nm and 8 nm, or between 2 nm and 5 nm.

[0055] In an embodiment, the conformal absorber layer 130 can be made of at least one material selected from the following: 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 conformal absorber layer 130 comprises W. In an embodiment, ALD is used to deposit the conformal absorber layer 130 because ALD allows for uniform deposition of materials at a desired thickness. Other deposition methods are difficult to deposit a uniform layer with a thickness below 20 nm.

[0056] In an embodiment, the second conformal barrier layer 121 has a thickness less than or equal to 50 nm, such as less than or equal to 45 nm, less than or equal to 40 nm, less than or equal to 35 nm, less than or equal to 30 nm, less than or equal to 25 nm, less than or equal to 20 nm, less than or equal to 15 nm, less than or equal to 10 nm, less than or equal to 5 nm, or less than or equal to 2 nm. According to an embodiment, the second conformal barrier layer has a thickness greater than or equal to 1 nm and less than or equal to 50 nm, such as greater than or equal to 1 nm and less than or equal to 45 nm, greater than or equal to 1 nm and less than or equal to 40 nm, greater than or equal to 1 nm and less than or equal to 35 nm, greater than or equal to 1 nm and less than or equal to 30 nm, or greater than or equal to 1 nm and less than or equal to 25 nm. In one or more embodiments, the second conformal barrier layer has a thickness greater than or equal to 1 nm and less than or equal to 20 nm, such as greater than or equal to 1 nm and less than or equal to 15 nm, greater than or equal to 1 nm and less than or equal to 10 nm, greater than or equal to 1 nm and less than or equal to 5 nm, greater than or equal to 1 nm and less than or equal to 2 nm, greater than or equal to 2 nm and less than or equal to 20 nm, greater than or equal to 2 nm and less than or equal to 15 nm, greater than or equal to 2 nm and less than or equal to 10 nm, greater than or equal to 2 nm and less than or equal to 5 nm, greater than or equal to 5 nm and less than or equal to 20 nm, greater than or equal to 5 nm and less than or equal to 15 nm, greater than or equal to 5 nm and less than or equal to 10 nm, greater than or equal to 10 nm and less than or equal to 20 nm, greater than or equal to 10 nm and less than or equal to 20 nm, greater than or equal to 15 nm and less than or equal to 20 nm, or greater than or equal to 15 nm and less than or equal to 20 nm.

[0057] In an embodiment, the second conformal barrier layer 131 can be formed of SiO2, MgF2, KBr, ZnO, or Al2O3 and can be applied to the conformal absorber layer 130 by chemical vapor deposition (CVD), physical vapor deposition (PVD), wet chemical methods, or ALD.

[0058] In an embodiment, the second conformal dielectric layer 140 may have a thickness greater than 0.1 quarter-wavelength (QW) to less than or equal to 4.0 QWs, where the control wavelength is determined by the target wavelength at the peak reflectivity in the visible light wavelength, such as between 0.5 QW and 4.0 QWs, between 1.0 QW and 4.0 QWs, between 1.5 QW and 4.0 QWs, between 2.0 QW and 4.0 QWs, between 2.5 QW and 4.0 QWs, between 3.0 QW and 4.0 QWs, or between 3.5 QW and 4.0 QWs. In an embodiment, the second conformal dielectric layer 140 may have a thickness from greater than 0.1 QW to less than 3.5 QWs, such as greater than 0.1 QW to less than 3.0 QWs, greater than 0.1 QW to less than 2.5 QWs, greater than 0.1 QW to less than 2.0 QWs, greater than 0.1 QW to less than 1.5 QWs, greater than 0.1 QW to less than 1.0 QWs, or greater than 0.1 QW to less than 0.5 QWs. In some embodiments, the second conformal dielectric layer 140 may have a thickness of 0.5 QW to 3.5 QWs, such as 1.0 QW to 3.0 QWs, or 1.5 QW to 2.5 QWs. In an embodiment, the target wavelength may be about 1050 nm.

[0059] In an embodiment, the second conformal dielectric layer 140 may be formed of TiO2 (including anatase, rutile, or amorphous TiO2 and mixtures thereof), ZnS, ZrO2, HfO2, Fe3O4, or AlAs. In one or more embodiments, the second conformal dielectric layer 140 may be made of a high refractive index absorptive dielectric material, such as Fe2O3, PbS, GaAs, InAs. In an embodiment, the second conformal dielectric layer 140 may be made of a low refractive index material, such as SiO2, MgF2, KBr, ZnO, or Al2O3. In an embodiment, the second conformal dielectric layer 140 may be deposited by CVD or ALD.

[0060] In an embodiment, the second conformal dielectric layer 140 may have a thickness between 5 nm 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, the second conformal dielectric layer 140 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 an embodiment, the second conformal dielectric layer 140 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.

[0061] According to an embodiment, the conformal outer layer 141 has a thickness less than or equal to 50 nm and greater than or equal to 5 nm, such as less than or equal to 40 nm and greater than or equal to 5 nm, less than or equal to 30 nm and greater than or equal to 5 nm, less than or equal to 20 nm and greater than or equal to 5 nm, less than or equal to 10 nm and greater than or equal to 5 nm, less than or equal to 50 nm and greater than or equal to 10 nm, less than or equal to 40 nm and greater than or equal to 10 nm, less than or equal to 30 nm and greater than or equal to 10 nm, less than or equal to 20 nm and greater than or equal to 10 nm, less than or equal to 50 nm and greater than or equal to 20 nm, less than or equal to 40 nm and greater than or equal to 20 nm, less than or equal to 30 nm and greater than or equal to 20 nm, less than or equal to 50 nm and greater than or equal to 30 nm, less than or equal to 40 nm and greater than or equal to 30 nm, or less than or equal to 50 nm and greater than or equal to 40 nm.

[0062] In an embodiment, the conformal outer layer 141 may be formed of silicon dioxide (SiO2), MgF2, KBr, ZnO, Al2O3, and may be applied to the conformal absorber layer 130 by CVD, PVD, wet chemical methods, or ALD.

[0063] In one or more embodiments, each of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 has a pore volume less than or equal to 0.030 cm 3 / g, such as less than or equal to 0.025 cm3 / g, less than or equal to 0.020 cm 3 / g, or less than or equal to 0.015 cm 3 / g. In an embodiment, each of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 has a pore volume of less than or equal to 0.010 cm 3 / g, such as less than or equal to 0.009 cm 3 / g, less than or equal to 0.008 cm 3 / g, less than or equal to 0.007 cm 3 / g, less than or equal to 0.006 cm 3 / g, less than or equal to 0.005 cm 3 / g, less than or equal to 0.004 cm 3 / g, less than or equal to 0.003 cm 3 / g, less than or equal to 0.002 cm 3 / g, less than or equal to 0.001 cm 3 / g. It should be understood that in an embodiment, one or more of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 may have the same pore volume, and in other embodiments, one or more of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 may have different pore volumes.

[0064] In one or more embodiments, the surface area of each of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 is less than or equal to 100 square meters per gram (m 2 / g), such as less than or equal to 90 m 2 / g, less than or equal to 85 m 2 / g, less than or equal to 80 m 2 / g, less than or equal to 75 m 2 / g, less than or equal to 70 m 2 / g, less than or equal to 65 m 2 / g, less than or equal to 60 m 2 / g, less than or equal to 55 m 2 / g, less than or equal to 50 m 2 / g, less than or equal to 45 m 2 / g, less than or equal to 40 m 2 / g, less than or equal to 35 m 2 / g, less than or equal to 30 m 2 / g, less than or equal to 25 m 2 / g, less than or equal to 20 m 2 / g, or less than or equal to 15 m 2 / g. In an embodiment, the surface area of each of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 is each less than or equal to 10 m 2 / g, such as less than or equal to 9 m 2 / g, less than or equal to 8 m 2 / g, less than or equal to 7 m 2 / g, less than or equal to 6 m 2 / g, less than or equal to 5 m 2 / g, less than or equal to 4 m 2 / g, less than or equal to 3 m 2 / g, less than or equal to 2 m 2 / g, or less than or equal to 1 m 2 / g. Thus, in an embodiment, the surface area of each of the layers may each be 2 m 2 / g to 10 m 2 / g, 3 m 2 / g to 10 m 2 / g, 3 m 2 / g to 8 m 2 / g, 5 m 2 / g to 8 m 2 / g, 1 m 2 / g to 3 m 2 / g, 3 m 2 / g to 5 m 2 / g, 2 m 2 / g to 3 m 2 / g, 1 m 2 / g to 2 m 2 / g, or 0.5 m 2 / g to 1 m 2 / g. It should be understood that in an embodiment, one or more of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 may have the same surface area, while in other embodiments, one or more of the core layer 110, the first conformal dielectric layer 120, the conformal absorber layer 130, and the second conformal dielectric layer 140 may have different surface areas.

[0065] The isotherm was collected by physical adsorption of nitrogen at 76 K to obtain the specific surface area (SSA) of the material by fitting 13 points collected from P / P0 ≈ 0.06 - 0.3 to the Brunauer - Emmett - Teller (BET) equation. Additional adsorption points were collected at various P / P0 up to P / P0 ≈ 0.95, and then desorbed back to P / P0 ≈ 0.06. The total pore volume was determined by the volume of nitrogen gas adsorbed at P / P0 0.95, and the average pore diameter was calculated using the Barrett Joyner Halenda (BJH) method.

[0066] In an embodiment, the multilayer structure may have a D measured by the BET equation 50 diameter, and the amount of adsorbed gas that forms a monolayer on the surface can be calculated from the measured isotherm. The number of molecules in the monolayer multiplied by the required space for one molecule gives the BET D 50, which is from 1 μm to 500 μm, such as 10 μm to 500 μm, 20 μm to 500 μm, 25 μm to 500 μm, 50 μm to 500 μm, 100 μm to 500 μm, 150 μm to 500 μm, 200 μm to 500 μm, 250 μm to 500 μm, 300 μm to 500 μm, 350 μm to 500 μm, 400 μm to 500 μm, 450 μm to 500 μm, 5 μm to 450 μm, 10 μm to 450 μm, 20 μm to 450 μm, 25 μm to 450 μm, 50 μm to 450 μm, 100 μm to 450 μm, 150 μm to 450 μm, 200 μm to 450 μm, 250 μm to 450 μm, 300 μm to 450 μm, 350 μm to 450 μm, 400 μm to 450 μm, 5 μm to 400 μm, 10 μm to 400 μm, 20 μm to 400 μm, 25 μm to 400 μm, 50 μm to 400 μm, 100 μm to 400 μm, 150 μm to 400 μm, 200 μm to 400 μm, 250 μm to 400 μm, 300 μm to 400 μm, 350 μm to 400 μm, 5 μm to 350 μm, 10 μm to 350 μm, 20 μm to 350 μm, 25 μm to 350 μm, 50 μm to 350 μm, 100 μm to 350 μm, 150 μm to 350 μm, 200 μm to 350 μm, 250 μm to 350 μm, 300 μm to 350 μm, 5 μm to 300 μm, 10 μm to 300 μm, 20 μm to 300 μm, 25 μm to 300 μm, 50 μm to 300 μm, 100 μm to 300 μm, 150 μm to 300 μm, 200 μm to 300 μm, 250 μm to 300 μm, 5 μm to 250 μm, 10 μm to 250 μm, 20 μm to 250 μm, 25 μm to 250 μm, 50 μm to 250 μm, 100 μm to 250 μm, 150 μm to 250 μm, 200 μm to 250 μm, 5 μm to 200 μm, 10 μm to 200 μm, 20 μm to 200 μm, 25 μm to 200 μm, 50 μm to 200 μm, 100 μm to 200 μm, 150 μm to 200 μm, 5 μm to 150 μm, 10 μm to 150 μm, 20 μm to 150 μm, 25 μm to 150 μm, 50 μm to 150 μm, 100 μm to 150 μm, 5 μm to 100 μm, 10 μm to 100 μm, 20 μm to 100 μm, 25 μm to 100 μm, 50 μm to 100 μm, 5 μm to 50 μm, 10 μm to 50 μm, 20 μm to 50 μm, 25 μm to 50 μm, 5 μm to 25 μm, 10 μm to 25 μm, 20 μm to 25 μm, 5 μm to 20 μm,10 μm to 20 μm, or 5 μm to 10 μm.

[0067] The aspect ratio of the multilayer structure according to the embodiments disclosed and described herein is from 1 to 100, measured by electron microscopy (TEM, SEM), both on the cross-section and on the surface, based on a large number of slices, such as 5 to 100, 10 to 100, 20 to 100, 30 to 100, 40 to 100, 50 to 100, 60 to 100, 70 to 100, 80 to 100, 90 to 100, 5 to 90, 10 to 90, 20 to 90, 30 to 90, 40 to 90, 50 to 90, 60 to 90, 70 to 90, 80 to 90, 5 to 80, 10 to 80, 20 to 80, 30 to 80, 40 to 80, 50 to 80, 60 to 80, 70 to 80, 5 to 70, 10 to 70, 20 to 70, 30 to 70, 40 to 70, 50 to 70, 60 to 70, 5 to 60, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 5 to 50, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 5 to 40, 10 to 40, 20 to 40, 30 to 40, 10 to 40, 20 to 40, 30 to 40, 5 to 30, 10 to 30, 20 to 30, 5 to 20, 10 to 20, or 5 to 10.

[0068] When viewed at an angle from 0° to 45°, the embodiments of the multilayer structure 100 have a hue shift of less than 30° in the Lab color space, such as less than 25°, less than 20°, less than 15°, or less than 10°.

[0069] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a conformal protective layer 111 made of SiO2 encapsulating the reflective core layer 110, a conformal dielectric layer 120 made of TiO2 encapsulating the conformal protective layer 111, a conformal barrier layer 121 made of Al2O3 encapsulating the conformal dielectric layer 120, and a conformal metal absorber layer 130 made of W encapsulating the conformal barrier layer 121.

[0070] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a first conformal protective layer 111 made of SiO2 encapsulating the reflective core layer 110, a first conformal dielectric layer 120 made of TiO2 encapsulating the conformal protective layer 111, a conformal barrier layer 121 made of Al2O3 encapsulating the conformal dielectric layer 120, a conformal metal absorber layer 130 made of W encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 made of SiO2 or Al2O3 encapsulating the conformal metal absorber layer 130, and a second conformal dielectric layer 140 made of TiO2 encapsulating the second conformal barrier layer 131.

[0071] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a first conformal protective layer 111 made of SiO2 encapsulating the reflective core layer 110, a first conformal dielectric layer 120 made of TiO2 encapsulating the conformal protective layer 111, a conformal barrier layer 121 made of Al2O3 encapsulating the conformal dielectric layer 120, a conformal metal absorber layer 130 made of W encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 made of SiO2 or Al2O3 encapsulating the conformal metal absorber layer 130, a second conformal dielectric layer 140 made of TiO2 encapsulating the second conformal barrier layer 131, and a conformal outer layer 141 made of SiO2 encapsulating the second conformal dielectric layer.

[0072] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a conformal protective layer 111 made of SiO2 encapsulating the reflective core layer 110, a conformal dielectric layer 120 made of Fe2O3 encapsulating the conformal protective layer 111, a conformal barrier layer 121 made of Al2O3 encapsulating the conformal dielectric layer 120, and a conformal metal absorber layer 130 made of W encapsulating the conformal barrier layer 121.

[0073] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a first conformal protective layer 111 made of SiO2 encapsulating the reflective core layer 110, a first conformal dielectric layer 120 made of Fe2O3 encapsulating the conformal protective layer 111, a conformal barrier layer 121 made of Al2O3 encapsulating the conformal dielectric layer 120, a conformal metal absorber layer 130 made of W encapsulating the conformal barrier layer 121, a second conformal barrier layer 131 made of SiO2 or Al2O3 encapsulating the conformal metal absorber layer 130, and a second conformal dielectric layer 140 made of Fe2O3 or TiO2 encapsulating the second conformal barrier layer 131.

[0074] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a first conformal protective layer 111 made of SiO2 that encapsulates the reflective core layer 110, a first conformal dielectric layer 120 made of Fe2O3 that encapsulates the conformal protective layer 111, a conformal barrier layer 121 made of Al2O3 that encapsulates the conformal dielectric layer 120, a conformal metal absorber layer 130 made of W that encapsulates the conformal barrier layer 121, a second conformal barrier layer 131 made of SiO2 or Al2O3 that encapsulates the conformal metal absorber layer, a second conformal dielectric layer 140 made of Fe2O3 or TiO2 that encapsulates the second conformal barrier layer 131, and a conformal outer layer 141 made of SiO2 that encapsulates the second conformal dielectric layer.

[0075] The multilayer structures in the embodiments disclosed herein can be used as pigments (e.g., paint pigments for coatings, for coating objects), or as continuous films applied to objects. When used as pigments, at least one of a paint binder and a filler can be used and mixed with the pigment to provide a coating that exhibits high-chroma structural color. Additionally, other additives can be added to the multilayer structure to aid in the compatibility of the multilayer structure in the coating system. Exemplary compatibility-enhancing additives include silane surface treatment agents that coat the exterior of the multilayer structure and improve the compatibility of the multilayer structure in the coating system. Such a coating system or film can be used on any article, including motor vehicles.

[0076] A first aspect includes a multilayer structure that reflects color and includes: a core layer; a conformal dielectric layer that encapsulates the core layer; a conformal barrier layer that encapsulates the conformal dielectric layer; and a conformal absorber layer that encapsulates the conformal barrier layer.

[0077] A second aspect includes the multilayer structure according to the first aspect, further including a conformal protective layer that encapsulates the core layer.

[0078] A third aspect includes the multilayer structure according to the first or second aspect, further including: a second conformal barrier layer that encapsulates the conformal absorber layer; and a second conformal dielectric layer that encapsulates the second conformal barrier layer.

[0079] A fourth aspect includes the multilayer structure according to any one of the first to third aspects, wherein the multilayer structure reflects a single narrow band of visible light when exposed to broadband electromagnetic radiation, and the single narrow band of visible light includes: when the multilayer structure is exposed to broadband electromagnetic radiation and viewed from an angle between 0° and 45° relative to the normal direction of the outer surface of the multilayer structure, the color shift of the single narrow band of visible light measured in the Lab color space is less than 30°.

[0080] The fifth aspect includes the multilayer structure according to any one of the first to fourth aspects, wherein the core layer has a thickness between 20 nm and 100 μm.

[0081] The sixth aspect includes the multilayer structure according to any one of the first to fifth aspects, wherein the conformal dielectric layer is formed of TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, or Al2O3, and the conformal dielectric layer has a thickness between 5 nm and 500 nm.

[0082] The seventh aspect includes the multilayer structure according to any one of the first to sixth aspects, wherein the conformal absorber layer is formed of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide, or a combination thereof, and the conformal metal absorber layer has a thickness between 2 nm and 50 nm.

[0083] The eighth aspect includes the multilayer structure according to any one of the first to seventh aspects, wherein the conformal barrier layer is formed of Al2O3, SiO2, MgF2, KBr, or ZnO, and the conformal barrier layer has a thickness less than or equal to 50 nm.

[0084] The ninth aspect includes the multilayer structure according to any one of the third to eighth aspects, wherein the second conformal dielectric layer is formed of TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, or Al2O3 and has a thickness between 5 nm and 500 nm, the conformal protective layer is formed of SiO2, MgF2, KBr, ZnO, or Al2O3 and has a thickness less than or equal to 50 nm, and the second conformal barrier layer is formed of SiO2, MgF2, KBr, ZnO, or Al2O3 and has a thickness less than or equal to 50 nm.

[0085] The tenth aspect includes the multilayer structure according to any one of the first to ninth aspects, wherein the core layer is formed of Al, the conformal dielectric layer is formed of TiO2 or Fe2O3, the conformal barrier layer is formed of Al2O3, and the conformal absorber layer is formed of W.

[0086] The eleventh aspect includes the multi-layer structure according to any one of the first to ninth aspects, wherein the core layer is formed of Al, the conformal protective layer is formed of SiO2, the conformal dielectric layer is formed of TiO2 or Fe2O3, the conformal barrier layer is formed of Al2O3, the conformal metal absorber layer is formed of W, the second conformal barrier layer is formed of SiO2 or Al2O3, and the second conformal dielectric layer is formed of TiO2 or Fe2O3.

[0087] The twelfth aspect includes the multi-layer structure according to any one of the first to eleventh aspects, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a pore volume of less than or equal to 0.030 cm 3 / g.

[0088] The thirteenth aspect includes the multi-layer structure according to any one of the first to twelfth aspects, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a pore volume of less than or equal to 0.005 cm 3 / g.

[0089] The fourteenth aspect includes the multi-layer structure according to any one of the first to thirteenth aspects, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a surface area of less than or equal to 100 m 2 / g.

[0090] The fifteenth aspect includes the multi-layer structure according to any one of the first to fourteenth aspects, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a surface area of less than or equal to 3 m 2 / g.

[0091] The sixteenth aspect includes the multi-layer structure according to any one of the first to fifteenth aspects, wherein the multi-layer structure has a D of 1 μm to 500 μm 50 diameter.

[0092] The seventeenth aspect includes the multi-layer structure according to any one of the first to sixteenth aspects, wherein the multi-layer structure has an aspect ratio of 1 to 100.

[0093] The eighteenth aspect includes a method for forming the multi-layer structure according to any one of the first to seventeenth aspects, the method comprising: depositing the conformal dielectric layer on the core layer by CVD or ALD; depositing the conformal barrier layer on the conformal dielectric layer by ALD; and depositing the conformal absorber layer on the conformal dielectric layer by ALD.

[0094] The nineteenth aspect includes a coating system comprising: a binder; and a multilayer structure according to any one of the first to seventeenth aspects.

[0095] The twentieth aspect includes a motor vehicle comprising the coating system according to the nineteenth aspect.

[0096] Note that in this document, the terms “substantially” and “about” may be used to represent the inherent degree of uncertainty attributable to any quantitative comparison, numerical value, measurement, or other representation. These terms are also used in this document to represent the degree to which a quantitative representation may vary from a reference value without causing a fundamental change in the basic function of the subject matter being discussed. Examples

[0097] The embodiments will be further illustrated by the following examples.

[0098] As described above, high-throughput ALD production can result in the overlap of adjacent dielectric layers and absorber layers, which can lead to the deterioration of the optical properties of the multilayer structure. It is believed that this overlap occurs due to the high porosity of the dielectric layer (such as the TiO2 layer), which allows overlap with the absorber layer (such as the W layer) applied by ALD because the metal can be impregnated into the pores of the dielectric layer. With the use of a barrier layer or a protective layer, all the layers are well separated, and thus their optical properties can be well predicted by simulation. Example 1

[0099] A multilayer structure was formed using an ALD process. The multilayer structure includes an aluminum reflective core layer, a conformal SiO2 first protective layer encapsulating the reflective core layer, a conformal TiO2 dielectric layer encapsulating the conformal SiO2 first protective layer, a conformal Al2O3 barrier layer encapsulating the conformal TiO2 dielectric layer, and a conformal W metal absorber layer encapsulating the conformal Al2O3 barrier layer.

[0100] Figure 6A is a TEM image of the formed multilayer structure. As Figure 6A shown, the layers are distinct, separated, and have smooth surfaces. Figure 6B is a further magnified TEM image of the formed multilayer structure and further shows distinct, separated, and smooth layers. Figure 6C is a TEM image in which elemental aluminum is highlighted. Figure 6C shows that the Al reflective core layer 710 is very distinct and has a smooth surface, and it also shows a distinct Al2O3 barrier layer 731, both of which have smooth surfaces. Figure 6D is a TEM image in which elemental oxygen is highlighted. Figure 6DShow a distinct SiO2 protective layer 711, a distinct TiO2 dielectric layer 720, and a distinct Al2O3 barrier layer 731, all of which have smooth surfaces and there is no significant overlap between the respective oxygen-containing layers. Figure 6E is a TEM image highlighting the element tungsten. As Figure 6E shown, the W absorber layer 730 is distinct and has a smooth surface. Figure 6E It is also shown that no tungsten penetrates into the TiO2 dielectric layer 720. Figure 6F is a TEM image highlighting the element titanium. Figure 6F Show a distinct TiO2 dielectric layer 720 with a smooth surface, and TiO2 does not penetrate into the Al reflective core layer 710 or the W absorber layer 730. Comparative Example 1

[0101] A multilayer structure is formed using an ALD process. The multilayer structure includes an aluminum reflective core layer, a conformal SiO2 first protective layer encapsulating the reflective core layer, a conformal TiO2 dielectric layer encapsulating the conformal SiO2 first protective layer, and a conformal W metal absorber layer encapsulating the conformal TiO2 dielectric layer. There is no barrier layer between the TiO2 dielectric layer and the W absorber layer.

[0102] Figure 7A is a TEM image of the formed multilayer structure. As Figure 7A shown, tungsten from the W absorber layer penetrates into the TiO2 dielectric layer. Figure 7B is a further magnified TEM image of the formed multilayer structure, and it is further shown that W penetrates into the TiO2 dielectric layer. Figure 7C is a TEM image highlighting the element aluminum. Figure 7C Show that the Al reflective core layer 710 is very distinct and has a smooth surface, and this smooth surface is partially provided by the SiO2 protective layer. Figure 7D is a TEM image highlighting the element oxygen. Figure 7D Show a higher oxygen concentration at the bottom of the TiO2 dielectric layer (i.e., closer to the Al reflective core layer), and less tungsten can penetrate here. Figure 7E is a TEM image highlighting the element tungsten. As Figure 7E shown, there is no protective layer and W penetrates into TiO2. Figure 7F is a TEM image highlighting the element titanium. Figure 7F Show a higher Ti concentration at the bottom of the TiO2 dielectric layer (i.e., closer to the Al reflective core layer), and less tungsten can penetrate here.

[0103] As shown in Example 1 and Comparative Example 1 above, by depositing an Al2O3 barrier layer between the TiO2 dielectric layer and the W absorber layer, the multilayer structure has a well-separated dielectric layer and absorber layer, and the resulting multilayer structure has improved chromaticity compared to the multilayer structure without a barrier layer between the TiO2 dielectric layer and the W absorber layer.

[0104] Those skilled in the art will appreciate that various modifications and alterations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Accordingly, this specification is intended to cover modifications and alterations of the various embodiments described herein, provided they fall within the scope of the appended claims and their equivalents.

Claims

1. A multi-layer structure that reflects color, comprising: A core layer; A conformal dielectric layer encapsulating the core layer; A conformal barrier layer encapsulating the conformal dielectric layer; and A conformal absorber layer encapsulating the conformal barrier layer.

2. The multi-layer structure according to claim 1, further comprising a conformal protective layer encapsulating the core layer.

3. The multi-layer structure according to claim 2, further comprising: A second conformal barrier layer encapsulating the conformal absorber layer; and A second conformal dielectric layer encapsulating the second conformal barrier layer.

4. The multi-layer structure according to claim 1, wherein the multi-layer structure reflects a single narrow band of visible light when exposed to broadband electromagnetic radiation, and the single narrow band of visible light includes: When the multi-layer structure is exposed to broadband electromagnetic radiation and viewed at an angle between 0° and 45° from the normal direction of the outer surface of the multi-layer structure, the color shift of the single narrow band of visible light measured in the Lab color space is less than 30°.

5. The multi-layer structure according to claim 1, wherein the core layer has a thickness between 20 nm and 100 μm.

6. The multi-layer structure according to claim 1, wherein The conformal dielectric layer is formed of TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO or Al2O3, and The conformal dielectric layer has a thickness between 5 nm and 500 nm.

7. The multi-layer structure according to claim 1, wherein The conformal absorber layer is formed of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide or a combination thereof, and The conformal absorber layer has a thickness between 2 nm and 50 nm.

8. The multi-layer structure according to claim 1, wherein The conformal barrier layer is formed of Al2O3, SiO2, MgF2, KBr or ZnO, and The conformal barrier layer has a thickness less than or equal to 50 nm.

9. The multi-layer structure according to claim 3, wherein The second conformal dielectric layer is formed of TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO or Al2O3 and has a thickness between 5 nm and 500 nm, The conformal protective layer is formed of SiO2, MgF2, KBr, ZnO or Al2O3 and has a thickness less than or equal to 50 nm, and The second conformal barrier layer is formed of SiO2, MgF2, KBr, ZnO or Al2O3 and has a thickness less than or equal to 50 nm.

10. The multi-layer structure according to claim 1, wherein The core layer is formed of Al, The conformal dielectric layer is formed of TiO2 or Fe2O3, The conformal barrier layer is formed of Al2O3, and The conformal absorber layer is formed of W.

11. The multi-layer structure according to claim 3, wherein the core layer is formed of Al, the conformal protective layer is formed of SiO2 or Al2O3, the conformal dielectric layer is formed of TiO2 or Fe2O3, the conformal barrier layer is formed of Al2O3, the conformal absorber layer is formed of W, the second conformal barrier layer is formed of SiO2 or Al2O3, and the second conformal dielectric layer is formed of TiO2 or Fe2O3.

12. The multilayer structure according to claim 1, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a pore volume of less than or equal to 0.030 cm 3 / g.

13. The multi-layer structure according to claim 1, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a pore volume of less than or equal to 0.005 cm 3 / g.

14. The multi-layer structure according to claim 1, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a surface area of less than or equal to 100 m 2 / g.

15. The multi-layer structure according to claim 1, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer has a surface area of less than or equal to 5 m 2 / g.

16. The multi-layer structure according to claim 1, wherein the multi-layer structure has a D of 1 μm to 500 μm 50 diameter.

17. The multi-layer structure according to claim 1, wherein the multi-layer structure has an aspect ratio of 1 to 100.

18. A method for forming the multi-layer structure according to claim 1, the method comprising: depositing the conformal dielectric layer on the core layer by CVD or ALD; depositing the conformal barrier layer on the conformal dielectric layer by ALD; and depositing the conformal absorber layer on the conformal dielectric layer by ALD.

19. A coating system, comprising: a binder; and the multi-layer structure according to claim 1.

20. A motor vehicle, comprising the coating system according to claim 19.

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