Three-layer structure color multilayer structure

Abstract

A multilayer structure that reflects color includes a core layer, and a conformal dielectric layer that encapsulates the core layer. A conformal absorber layer encapsulates the conformal dielectric layer. The multilayer structure is composed of three optical layers.

Description

Cross - Reference to Related Applications

[0001] This application claims the benefit of priority of U.S. Patent Application No. 18 / 116,601, filed Mar. 2, 2023, which claims the benefit of priority of U.S. Provisional Application No. 63 / 404,416, filed Sep. 7, 2022, the content of which is hereby incorporated by reference in its entirety. Technical Field

[0002] The present disclosure relates to multilayer structures, and more particularly to multilayer structures comprising metals and metal oxides over a substrate, wherein at least one of the metals and metal oxides is deposited by atomic layer deposition. Background Art

[0003] Pigments made of multilayer structures are known. In addition, pigments that exhibit or provide structural color are also known. However, these prior - art pigments require nine, eleven, or more thin - film layers to obtain the desired color properties.

[0004] It will be appreciated that the cost associated with the production of multilayer pigments is proportional to the number of layers required. Thus, the cost associated with using a multilayer stack of dielectric materials to produce structural color can be excessive. Accordingly, a structural color that requires a minimum number of thin - film layers would be desirable. Summary of the Invention

[0005] According to an embodiment, a multilayer structure that reflects color comprises: a core layer; a conformal dielectric layer encapsulating the core layer; and a conformal absorber layer encapsulating the conformal dielectric layer, wherein the multilayer structure consists of three optical layers.

[0006] According to an embodiment, a method for forming a multilayer structure includes: depositing a conformal dielectric layer on a core layer by CVD or ALD; and depositing a conformal absorber layer on the conformal dielectric layer by ALD.

[0007] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, which embodiments include the detailed description, the claims, and the drawings.

[0008] It should be understood that the foregoing general description and the following detailed description both describe various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. The accompanying 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, are used to explain the principles and operations of the claimed subject matter. Description of the Drawings

[0009] Figure 1 is a schematic cross-section of a multi-layer structure according to embodiments disclosed and described herein;

[0010] Figure 2A depicts a multi-layer structure having a dielectric layer extending over a core layer used in the design of the multi-layer structure;

[0011] Figure 2B depicts a multi-layer structure having an absorber layer extending over a core layer used in the design of the multi-layer structure;

[0012] Figure 2C depicts a multi-layer structure having a dielectric layer extending over a core layer used in the design of a multi-layer structure according to one or more embodiments shown and described herein;

[0013] Figure 3 depicts Figures 2A - 2C the reflection characteristics of the multi-layer structure shown in the Lab color space;

[0014] Figure 4A graphically depicts Figure 2A the chromaticity and hue values of the multi-layer structure shown as a function of the dielectric layer thickness;

[0015] Figure 4B graphically depicts Figure 2B the chromaticity and hue values of the multi-layer structure shown as a function of the semiconductor absorber layer thickness;

[0016] Figure 4C graphically depicts Figure 2C the chromaticity and hue values of the multi-layer structure shown as a function of the dielectric layer thickness;

[0017] Figure 5 depicts a multi-layer 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;

[0018] Figure 6A is a coordinate plot of reflectance versus electromagnetic radiation wavelength, which shows the effect of tungsten absorber layer thickness; and

[0019] Figure 6B is a coordinate graph of reflectance relative to the wavelength of electromagnetic radiation, which shows TiO 2 the influence of the dielectric layer thickness. Detailed implementation mode

[0020] A color-generating structure is provided in the present disclosure. The color-generating structure has the form of a multilayer structure that can reflect a narrow band of electromagnetic radiation in the visible spectrum and has a small or insignificant hue shift when viewed from an angle between 0 and 45 degrees. The multilayer structure can be used as a pigment in a composition (such as, for example, a coating composition), a film on a structure, and the like.

[0021] Preparing a colored multilayer structure can be a complex and expensive process, in part because very strict control of the layer thickness is required. The deposition method for depositing a layer can vary in complexity and cost depending on the material that makes up a given layer and the desired thickness of the layer. Therefore, different materials that make up a given layer and the desired thickness of the layer.

[0022] However, depositing a layer directly on a reflective core layer such as an aluminum (Al) reflective core can be challenging and it may be difficult to deposit the material into a layer with a nanoscale thickness. Atomic layer deposition (ALD) is a technique that excels at both, but ALD deposition has been expensive and time-consuming to date. For example, ALD essentially deposits materials at the atomic level, so depositing a thick layer (such as a layer with a thickness greater than 500 nm) using the ALD process takes a lot of time. Therefore, ALD is typically not preferred for depositing each layer in a multilayer structure. Typically, due to cost and time limitations, ALD has been reserved for depositing very thin layers, and the layers produced by previous ALD methods can have poor coverage or high porosity, which makes it difficult to apply additional high-quality metal and / or metal oxide layers to the multilayer structure.

[0023] However, as disclosed herein, it has been found that depositing all layers of a multilayer structure using ALD provides layers with properties such as surface area and pore volume, which can allow a micro-layer structure with three layers to function in the same way as a multilayer structure with significantly more layers. Specifically, the embodiments disclosed herein use the ALD process to deposit a dense, pore-free metal and / or metal oxide layer on a reflector (such as Al). The quality of the layers deposited by ALD allows a three-layer OSC multilayer structure to have optical properties similar to those of five-layer and seven-layer OSC multilayer structures. By reducing the number of layers deposited into the multilayer structure, the manufacturing cost and time can be reduced.

[0024] The multi-layer structures described herein can be used to reflect visible light wavelengths over a range of incident or viewing angles (e.g., hues between 0° and 120°). It will be understood that the terms "electromagnetic wave", "electromagnetic radiation", and "light" as used herein may be interchangeably substituted to refer to light of various wavelengths incident on the multi-layer structure, and such light may have wavelengths in the ultraviolet (UV), infrared (IR), and visible portions of the electromagnetic spectrum.

[0025] As used herein, "core layer" refers to both reflective and non-reflective core layers, and the "core layer" can have any shape, including but not limited to sheets, spheres, ovals, etc. As used herein, "absorber layer" includes both metal and non-metal absorber layers.

[0026] Now referring to Figure 1 , the multi-layer structure 100 according to the embodiments disclosed and described herein includes: a core layer 110, a conformal dielectric layer 120 encapsulating the core layer 110, and a conformal absorber layer 130 encapsulating the conformal dielectric layer 120. The multi-layer structure 100 disclosed and described herein consists of three optical layers. These "optical layers" are the layers that affect the optics of the multi-layer structure 100, such as layers made of reflective, dielectric, and absorber materials, where the layers are thick enough to affect the optical properties of the multi-layer structure. The term "optical layer" as used herein does not include thin barrier layers that do not affect the optical properties of the multi-layer structure.

[0027] Referring to Figures 2A - 2C and Figure 3 , the effectiveness of different types of layers extending over the core layer 110 to obtain desired hue levels in a desired region of the visible spectrum, 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 a Fe 2 O 3 dielectric layer 120c extending over the reflective core layer 110 is depicted. Simulations of the reflectivity of each of the multi-layer structures shown are performed based on the different thicknesses of the dielectric layer 120a, the semiconductor absorber layer 120b, and the dielectric layer 120c. The results of this simulation are plotted in the Lab color space, also known as the a*b* color chart, as Figures 2A - 2C shown. Figure 3 Each data point shown in Figure 3 provides, for the dielectric layer of the multi-layer structure depicted in Figure 2A , the semiconductor absorber layer of the multi-layer structure depicted in Figure 2B , or Figure 2CThe chroma and hue of a specific thickness of the dielectric layer of the multilayer structure depicted in. Chroma can be defined as And hue can be defined as tan -1 (a* / b*). 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 with the multilayer structure shown in Figure 2B and 2C the multilayer structure shown in Figure 2A provides a low chroma. Therefore, Figures 2A - 2C and Figure 3 confirm that when a color with a high chroma is desired, as the first layer extending over the reflective core layer, the absorber layer is preferred over the dielectric layer. It should be understood that Figure 3 the Lab color space analysis shown in

[0028] is for illustrative purposes, and the multilayer structure 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. Figures 4A - 4C Referring to Figure 4A depicts the variation of chroma and hue with layer thickness. Specifically, Figure 2A graphically depicts the variation of chroma and hue with 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 Fe 2 O 3 dielectric layer extending over the Al reflective core layer. Figures 4A - 4C The dashed line in Figures 4A - 4C corresponds to the desired hue value between 10° and 30° on the Lab color space. Figure 4A shows that for a multilayer structure having a dielectric 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

[0029] Referring again to Figure 1, shows a multi-layer structure 100 of the reflected color according to an embodiment. The multi-layer structure 100 includes: a core layer 110, a conformal dielectric layer 120 encapsulating the core layer 110, and a conformal absorber layer 130 encapsulating the conformal dielectric layer 120. As Figure 1 shown, embodiments of the multi-layer 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 is consistent in size and shape with the layer onto which it is deposited and encapsulates (i.e., is present on all sides of) the layer onto which it is deposited. Although Figure 1 a rectangular structure is shown, this is for illustrative purposes only, and the multi-layer structure will generally have an asymmetric and non-uniform shape. In an embodiment, the multi-layer structure may be spherical or oval. It should be understood that the embodiment may also include a multi-layer structure having a conformal absorber encapsulating the core layer and a conformal dielectric layer encapsulating the conformal absorber layer.

[0030] 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 an embodiment, 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.

[0031] In an embodiment, the core layer 110 may be made of at least one of the following: "gray metal" materials such as Al, Ag, Pt, Sn; at least one of "colored metal" materials such as Au, Cu, brass, bronze, TiN, Cr, stainless steel, or combinations thereof. In one or more embodiments, the core layer 110 may be made of an oxide such as aluminum oxide (Al 2 O 3 ), silicon oxide (SiO 2 ), or a glass material. As described above, the core layer 110 may have a plate-like shape, or may be spherical or oval.

[0032] 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 can 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.,

[0033] In an embodiment, the conformal dielectric layer 120 is a high refractive index material such as TiO 2 (including anatase, rutile or amorphous TiO 2 and mixtures thereof), ZnS, ZrO 2 , HfO 2 , Fe 3 O 4 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 Fe 2 O 3 , PbS, GaAs or InAs. In an embodiment, the conformal dielectric layer may be made of a low refractive index material such as SiO 2 , MgF 2 , KBr, ZnO or Al 2 O 3. In an embodiment, the conformal dielectric layer 120 can be deposited by CVD, PVD, wet chemical methods, or ALD to encapsulate the core layer 110.

[0034] As Figure 1 shown, the conformal absorber layer 130 encapsulates the conformal dielectric layer 120. 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 of a hue of 10° to 30°, then the absorber layer is placed at a thickness where the electric field (|E| 2 ) at 550 nm wavelength is less than at 650 nm wavelength. Mathematically, this can be expressed as: |E 550 | 2 << |E 650 | 2 (1) Preferably: |E 650 | 2 ≈0 (2)

[0035] Figure 5 And the following discussion provides a method for calculating the thickness of the point of zero or near-zero electric field 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 substrate layer 2 is shown, the dielectric layer 4 having a total thickness "D", an incremental thickness "d", and a refractive index "n", the substrate layer 2 having a refractive index of "n s ". The substrate 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. 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 substrate 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 sinθs , where "s" corresponds to the substrate in Figure 7, and is the permittivity of the layer as a function of z. Thus: |E(d)| 2 = |u(z)| 2 exp(2ikαy)| z＝d (5) For s-polarization, and For p-polarization.

[0036] 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 relationships: q s = n s cosθ s For s-polarization (8) q s = n s / cosθ s For p-polarization (9) q = ncosθ F For s-polarization (10) q = n / cosθ F For p-polarization (11) u(z) and v(z) can be expressed as: And Thus: For s-polarization, having And: For p-polarization, where: α = n s sinθ s = n sinθ F (17) And

[0037] Thus, 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 locus where the electric field within the dielectric layer is zero). It should be understood that the thickness “d” can be the thickness of the conformal dielectric layer 120 extending over the core layer 110 that provides zero or near-zero electric field at the interface between the 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 dielectric outer layer 140 extending over the conformal absorber layer 130 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.

[0038] 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.

[0039] 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 to a desired thickness. Other deposition methods have difficulty depositing a uniform layer with a thickness below 20 nm.

[0040] 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 of less than or equal to 0.030 cm 3 / g, such as less than or equal to 0.025 cm 3 / 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 conformal dielectric layer 120, and the conformal absorber layer 130 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 conformal dielectric layer 120, and the conformal absorber layer 130 may have the same pore volume, and in other embodiments, one or more of the core layer 110, the conformal dielectric layer 120, and the conformal absorber layer 130 may have different pore volumes.

[0041] 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 m2 / 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, conformal dielectric layer 120, and conformal absorber layer 130 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 can 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. The surface area is measured by collecting the complete adsorption / desorption isotherm of the sample after degassing at 90 °C for one hour and then degassing to 150 °C for three hours. It should be understood that in some embodiments, one or more of the core layer 110, conformal dielectric layer 120, and conformal absorber layer 130 may have the same surface area, while in other embodiments, one or more of the core layer 110, conformal dielectric layer 120, and conformal absorber layer 130 may have different surface areas.

[0042] By fitting the 13 points collected from P / P 0 ≈ 0.06 - 0.3 to the Brunauer-Emmett-Teller (BET) equation, the isotherm is collected using 76K nitrogen physisorption to obtain the specific surface area (SSA) of the material. At each P / P 0 Additional adsorption points are collected until P / P 0 ≈ 0.95, and then desorption returns to P / P 0 ≈ 0.06. The total pore volume is determined by the volume of nitrogen gas adsorbed at P / P 0 0.95, and the average pore diameter is calculated using the Barrett Joyner Halenda (BJH) method.

[0043] In an embodiment, the multilayer structure may have a D 50 diameter measured by the BET equation, 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 is multiplied by the space required for one molecule to obtain the BET D 50, which is from 1 μm to 500 μm, such as from 10 μm to 500 μm, from 20 μm to 500 μm, from 25 μm to 500 μm, from 50 μm to 500 μm, from 100 μm to 500 μm, from 150 μm to 500 μm, from 200 μm to 500 μm, from 250 μm to 500 μm, from 300 μm to 500 μm, from 350 μm to 500 μm, from 400 μm to 500 μm, from 450 μm to 500 μm, from 5 μm to 450 μm, from 10 μm to 450 μm, from 20 μm to 450 μm, from 25 μm to 450 μm, from 50 μm to 450 μm, from 100 μm to 450 μm, from 150 μm to 450 μm, from 200 μm to 450 μm, from 250 μm to 450 μm, from 300 μm to 450 μm, from 350 μm to 450 μm, from 400 μm to 450 μm, from 5 μm to 400 μm, from 10 μm to 400 μm, from 20 μm to 400 μm, from 25 μm to 400 μm, from 50 μm to 400 μm, from 100 μm to 400 μm, from 150 μm to 400 μm, from 200 μm to 400 μm, from 250 μm to 400 μm, from 300 μm to 400 μm, from 350 μm to 400 μm, from 5 μm to 350 μm, from 10 μm to 350 μm, from 20 μm to 350 μm, from 25 μm to 350 μm, from 50 μm to 350 μm, from 100 μm to 350 μm, from 150 μm to 350 μm, from 200 μm to 350 μm, from 250 μm to 350 μm, from 300 μm to 350 μm, from 5 μm to 300 μm, from 10 μm to 300 μm, from 20 μm to 300 μm, from 25 μm to 300 μm, from 50 μm to 300 μm, from 100 μm to 300 μm, from 150 μm to 300 μm, from 200 μm to 300 μm, from 250 μm to 300 μm, from 5 μm to 250 μm, from 10 μm to 250 μm, from 20 μm to 250 μm, from 25 μm to 250 μm, from 50 μm to 250 μm, from 100 μm to 250 μm, from 150 μm to 250 μm, from 200 μm to 250 μm, from 5 μm to 200 μm, from 10 μm to 200 μm, from 20 μm to 200 μm, from 25 μm to 200 μm, from 50 μm to 200 μm, from 100 μm to 200 μm, from 150 μm to 200 μm, from 5 μm to 150 μm, from 10 μm to 150 μm, from 20 μm to 150 μm, from 25 μm to 150 μm, from 50 μm to 150 μm, from 100 μm to 150 μm, from 5 μm to 100 μm, from 10 μm to 100 μm, from 20 μm to 100 μm, from 25 μm to 100 μm, from 50 μm to 100 μm, from 5 μm to 50 μm, from 10 μm to 50 μm, from 20 μm to 50 μm, from 25 μm to 50 μm, from 5 μm to 25 μm, from 10 μm to 25 μm, from 20 μm to 25 μm, from 5 μm to 20 μm,10 μm to 20 μm, or 5 μm to 10 μm.

[0044] 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 thin 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.

[0045] 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°.

[0046] In one or more embodiments, the multilayer structure 100 comprises: a reflective core layer 110 made of Al, a conformal dielectric layer 120 deposited by ALD and made of TiO 2 and encapsulating the reflective core layer 110, and a conformal metal absorber layer 130 deposited by ALD and made of W and encapsulating the conformal dielectric layer 120.

[0047] In one or more embodiments, the multilayer structure 100 comprises: a reflective core layer 110 made of Al, a conformal dielectric layer 120 deposited by ALD and made of Fe 2 O 3 and encapsulating the reflective core layer 110, and a conformal metal absorber layer 130 deposited by ALD and made of W and encapsulating the conformal dielectric layer 120.

[0048] The multilayer structures in the embodiments disclosed herein can be used as pigments (e.g., paint pigments for coatings, for coating objects), or as a continuous structure 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 coating that exhibits omnidirectional structural color. Additionally, other additives can be added to the multilayer structure to aid in the compatibility of the multilayer structure in a 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 a coating system. Such a coating system or film can be used on any article, including motor vehicles.

[0049] As described herein, at least one of a metal or metal oxide layer (such as a conformal dielectric layer and a conformal absorber layer) can be deposited by ALD. Example embodiments of the ALD process for depositing these layers will be discussed in more detail below.

[0050] Furthermore, using the ALD process allows for the large-scale deposition of multiple layers with a large difference in optical precision and material properties (such as the dielectric material relative to the metal material as described above). Additionally, the ALD process allows for the production of multilayer structures with high density, low porosity, and complete layer coverage, all with nanoscale precision. Moreover, the deposition precision and non-destructive characteristics of ALD have little impact on existing vulnerable layers (e.g., Al core layers, etc.). It is difficult or expensive to achieve these results with other processes.

[0051] A first aspect includes a multilayer structure that reflects color, the multilayer structure comprising: a core layer; a conformal dielectric layer encapsulating the core layer; and a conformal absorber layer encapsulating the conformal dielectric layer, wherein the multilayer structure consists of three optical layers.

[0052] A second aspect includes the multilayer structure according to the first aspect, wherein the multilayer structure reflects a single narrow band of visible light when exposed to broadband electromagnetic radiation, the single narrow band of visible light including: when the multilayer structure is exposed to broadband electromagnetic radiation and viewed from an angle between 0° and 45° from the normal direction with respect to 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°.

[0053] A third aspect includes the multilayer structure of the first or second aspect, wherein the core layer is formed of Al, Ag, Pt, Sn, Au, Cu, brass, bronze, stainless steel, TiN, Cr, Al 2 O 3 、SiO 2 、glass, or a combination thereof.

[0054] The fourth aspect includes a multilayer structure according to the first to third aspects, wherein the core layer has a thickness between 20 nm and 100 μm.

[0055] The fifth aspect includes a multilayer structure according to the first to fourth aspects, wherein the conformal dielectric layer is made of TiO 2 , ZnS, ZrO 2 , HfO 2 , Fe 3 O 4 , AlAs, Fe 2 O 3 , PbS, GaAs, InAs, SiO 2 , MgF 2 , KBr, ZnO, Al 2 O 3 and combinations thereof.

[0056] The sixth aspect includes a multilayer structure according to the first to fifth aspects, wherein the conformal dielectric layer has a thickness between 5 nm and 500 nm.

[0057] The seventh aspect includes a multilayer structure according to the first to sixth aspects, wherein the conformal absorber layer is made of W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, iron oxide, or combinations thereof.

[0058] The eighth aspect includes a multilayer structure according to the first to seventh aspects, wherein the conformal absorber layer has a thickness between 2 nm and 50 nm.

[0059] The ninth aspect includes a multilayer structure according to the first to eighth aspects, wherein the core layer is made of Al, the conformal dielectric layer is made of TiO 2 , and the conformal absorber layer is made of W.

[0060] The tenth aspect includes a multilayer structure according to the first to eighth aspects, wherein the core layer is made of Al, the conformal dielectric layer is made of Fe 2 O 3 , and the conformal absorber layer is made of W.

[0061] The eleventh aspect includes a multilayer structure according to the first to tenth 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.

[0062] The twelfth aspect includes a multilayer structure according to 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 0.005 cm3 Pore volume per g.

[0063] The thirteenth aspect includes a multilayer structure according to the first to twelfth 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.

[0064] The fourteenth aspect includes a multilayer structure according to 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 5 m 2 / g.

[0065] The fifteenth aspect includes a multilayer structure according to the first to fourteenth aspects, wherein the multilayer structure has a D of 1 μm to 500 μm 50 Diameter.

[0066] The sixteenth aspect includes a multilayer structure according to the first to fifteenth aspects, wherein the multilayer structure has an aspect ratio of 1 to 100.

[0067] The seventeenth aspect, a method for forming the multilayer structure according to the first to sixteenth aspects, the method comprising: depositing the conformal dielectric layer on the core layer by CVD or ALD; and depositing the conformal absorber layer on the conformal dielectric layer by ALD.

[0068] The eighteenth aspect includes a method for forming the multilayer structure according to the first to sixteenth aspects, the method comprising: depositing the conformal dielectric layer on the core layer by ALD; and depositing the conformal absorber layer on the conformal dielectric layer by ALD.

[0069] The nineteenth aspect includes a coating system comprising: a binder; and the multilayer structure according to any one of the first to sixteenth aspects.

[0070] The twentieth aspect includes a motor vehicle comprising the coating system according to the nineteenth aspect.

[0071] 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 quantity representation can vary from the reference value without causing a fundamental change in the basic function of the subject matter being discussed. Examples

[0072] The embodiments will be further illustrated by the following examples.

[0073] Example 1

[0074] A multi-layer structure formed by an ALD process deposits different smooth layers deposited as each layer in a three-layer multi-layer structure.

[0075] Example 2

[0076] For the TiO deposited by the ALD process of Example 1 2 dielectric layer and the TiO formed by a wet chemical process 2 dielectric layer are compared.

[0077] At 40 °C, the pigment was suspended in isopropyl alcohol (IPA) in a flask. A titanium ethoxide solution dissolved in IPA was titrated at a constant rate for 2.5 hours. At the same time, DI water diluted in IPA was metered in. After titration, the suspension was stirred for another 30 minutes. The mixture was cooled to room temperature, then filtered, washed with IPA and dried at 100 °C for 24 hours. Then the collected product was sintered at 300 - 500 °C for a period of 2 - 6 hours.

[0078] The dielectric layer deposited by the ALD process of Example 1 is smoother and denser than the dielectric layer formed by the wet chemical method.

[0079] Example 3

[0080] In this example, the effects of the tungsten metal absorber layer and the thickness of the TiO 2 dielectric layer were studied. Figure 6A Four samples made according to the ALD process of Example 1 are shown, differing in that the process was modified to provide tungsten metal absorber layers with thicknesses of 5 nm, 7 nm, 9 nm, and 12 nm. All of these samples have an Al reflective core layer and a 50 nm thick TiO 2 dielectric layer. As Figure 6A shown, as the thickness of the tungsten layer increases, the reflectivity curve shifts slightly to the left (lower wavelength) and becomes more reflective.

[0081] Figure 6B Four samples manufactured according to the ALD process of Example 1 are shown, differing in that the process was modified to provide TiO dielectric layers with thicknesses of 42 nm, 45 nm, 48 nm, and 50 nm. All of these samples have an Al reflective core layer and a 5 nm thick tungsten metal absorber layer. As 2 shown, as the thickness of the titanium dioxide layer increases, the reflectivity curve shifts slightly to the left (lower wavelength). However, the performance of each sample is significantly better than that of a seven-layer structure formed by vacuum deposition. Figure 6B shown, as the thickness of the titanium dioxide layer increases, the reflectivity curve shifts slightly to the left (lower wavelength). However, the performance of each sample is significantly better than that of a seven-layer structure formed by vacuum deposition.

[0082] Example 4

[0083] This example compares the density, surface area, and pore volume of the multilayer structures fabricated by the ALD process according to Example 1 and the wet chemical method described in Example 2. As shown in Table 1 below, the densities of the multilayer structures fabricated by ALD and the wet chemical method are the same, but the surface area of the multilayer structure using the ALD method is much smaller.

[0084] Table 1 Property ALD method Wet chemical method Density <![CDATA[2.8g / cm 3 > <![CDATA[2.8g / cm 3 > Surface area (BET) <![CDATA[3.6m 2 / g]]> <![CDATA[109.2m 2 / g]]> Pore volume (BET) <![CDATA[0.005cm 3 / g]]> <![CDATA[0.036cm 3 / g]]>

[0085] The density of the pigment is the ratio of the mass of the pigment sample to its volume, where the volume includes the contribution of the interparticle void volume. To measure this, a glass cylinder with a specific volume is used, and a known mass of the pigment is introduced into the cylinder. The volume is evaluated by adding DI water to the cylinder until the water reaches the volume line of the cylinder. The volume of the water is obtained by measuring the weight of how much DI water is added. The sample volume is obtained by subtracting the volume of the water from the total volume of the cylinder. Repeated experiments are conducted to determine the density. After degassing at 90 °C for one hour and then at 150 °C for three hours, a complete adsorption / desorption isotherm is collected on the sample. By fitting the 13 points collected from P / P 0 ≈ 0.06 - 0.3 to the Brunauer - Emmett - Teller (BET) equation, the isotherm is collected using physical adsorption of nitrogen gas at 76K to obtain the specific surface area (SSA) of the material. At each P / P 0 additional adsorption points are collected until P / P 0 ≈ 0.95, and then the desorption returns to P / P 0 ≈ 0.06. The total pore volume is determined by the volume of nitrogen gas adsorbed at P / P 0 0.95, and the Barrett Joyner Halenda (BJH) method is used to calculate the average pore diameter.

[0086] Those skilled in the art will appreciate that various modifications and changes 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 variations of the various embodiments described herein, provided such modifications and variations fall within the scope of the appended claims and their equivalents.

Claims

1. A multi-layer structure for reflecting color, the multi-layer structure comprising: A core layer; A conformal dielectric layer encapsulating the core layer; and A conformal absorber layer encapsulating the conformal dielectric layer, wherein The multi-layer structure is composed of three optical layers.

2. 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, the single narrow band of visible light Comprising: 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°.

3. The multi-layer structure according to claim 1, wherein the core layer is formed of Al, Ag, Pt, Sn, Au, Cu, brass, bronze, stainless steel, TiN, Cr, Al 2 O 3 , SiO 2 , glass, or a combination thereof.

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

5. The multilayer structure according to claim 1, wherein the conformal dielectric layer is composed of TiO 2 , ZnS, ZrO 2 , HfO 2 , Fe 3 O 4 , AlAs, Fe 2 O 3 , PbS, GaAs, InAs, SiO 2 , MgF 2 , KBr, ZnO, Al 2 O 3 and combinations thereof.

6. The multi-layer structure according to claim 1, wherein 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.

8. The multi-layer structure according to claim 1, wherein the conformal absorber layer has a thickness between 2 nm and 50 nm.

9. The multi-layer structure according to claim 1, wherein The core layer is formed of Al, The conformal dielectric layer is formed of TiO 2 and The conformal absorber layer is formed of W.

10. The multi-layer structure according to claim 1, wherein The core layer is formed of Al, The conformal dielectric layer is formed of Fe 2 O 3 and The conformal absorber layer is formed of W.

11. 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.

12. 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.

13. The multilayer 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.

14. The multilayer 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.

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

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

17. 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; And Depositing the conformal absorber layer on the conformal dielectric layer by ALD.

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 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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