Three-layer structural color multilayer structure

Abstract

The color-reflecting multilayer structure includes a core layer and 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.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application No. 63 / 404,416, filed September 7, 2022, the contents of which are relied upon and incorporated herein by reference in their entirety.

[0002] Field The present disclosure relates to multilayer structures, and in particular to multilayer structures comprising a metal and a metal oxide on a substrate, where at least one of the metal and the metal oxide is deposited by atomic layer deposition. [Background technology]

[0003] Pigments made from multilayer structures are known. Furthermore, pigments that exhibit or provide structural color are also known. However, such prior art pigments have required 9, 11, or more thin film layers to achieve the desired color properties.

[0004] It is known that the costs associated with manufacturing multilayer pigments are proportional to the number of layers required. Thus, the costs associated with producing structural colors using multilayer stacks of dielectric materials can be prohibitive. Therefore, structural colors that require a minimum number of thin film layers would be desirable. Summary of the Invention

[0005] According to an embodiment, the color-reflecting multilayer structure includes a core layer, a conformal dielectric layer encapsulating the core layer, and a conformal absorber layer encapsulating the conformal dielectric layer, the multilayer structure consisting of three optical layers.

[0006] According to an embodiment, a method of forming the multilayer structure includes depositing a conformal dielectric layer on a core layer by CVD (chemical vapor deposition) or ALD (atomic layer deposition), and depositing a conformal absorber layer on the conformal dielectric layer by ALD.

[0007] Additional features and advantages are set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the detailed description, or will become apparent to those skilled in the art by practicing the embodiments described in this disclosure, which includes the following detailed description, the claims, and the accompanying drawings.

[0008] It is to be understood that both the foregoing general description and the following detailed description are intended to describe various embodiments and provide an overview or framework for understanding the nature and features of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments described in the present disclosure and, together with the detailed description, serve to explain the principles and operation of the claimed subject matter. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of a multi-layer structure according to an embodiment disclosed and described herein.

[0010] [Figure 2A] FIG. 2A shows a multilayer structure with a dielectric layer extending over a core layer used in the design of the multilayer structure.

[0011] [Figure 2B] FIG. 2B shows a multi-layer structure with an absorber layer extending over the core layer used in the design of the multi-layer structure.

[0012] [Figure 2C]FIG. 2C illustrates a multi-layer structure having a dielectric layer extending over a core layer for use in the design of a multi-layer structure according to one or more embodiments disclosed and described herein.

[0013] [Figure 3] FIG. 3 shows the reflection characteristics of the multilayer structure shown in FIGS. 2A to 2C in the Lab color space.

[0014] [Figure 4A] FIG. 4A graphically illustrates saturation and hue values ​​as a function of dielectric layer thickness for the multi-layer structure shown in FIG. 2A.

[0015] [Figure 4B] FIG. 4B graphically illustrates saturation and hue values ​​as a function of semiconductor absorber layer thickness for the multilayer structure shown in FIG. 2B.

[0016] [Figure 4C] FIG. 4C graphically illustrates saturation and hue values ​​as a function of dielectric layer thickness for the multilayer structure shown in FIG. 2C.

[0017] [Figure 5] FIG. 5 illustrates a multilayer structure having a dielectric layer extending over a substrate layer and exposed to electromagnetic radiation at an angle θ relative to a direction normal to the outer surface of the dielectric layer.

[0018] [Figure 6A] FIG. 6A is a graph of reflectance versus wavelength of electromagnetic radiation showing the effect of tungsten absorber layer thickness.

[0019] [Figure 6B] FIG. 6B is a graph of reflectance versus wavelength of electromagnetic radiation showing the effect of the thickness of the TiO 2 dielectric layer. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present disclosure provides color-producing structures in the form of multilayer structures capable of reflecting a narrow band of electromagnetic radiation in the visible spectrum, with a small or insignificant hue shift when the multilayer structure is viewed from an angle of 0 to 45 degrees. The multilayer structures can be used as pigments in compositions (e.g., paint compositions), films on structures, and the like.

[0021] Fabricating color multilayer structures can be a complex and expensive process, in part because very tight control of layer thickness is required. The deposition methods used to deposit the layers can vary in complexity and cost, depending on the materials that make up a given layer and the desired thickness of the layer. Thus, different materials can make up a given layer and the desired thickness of the layer.

[0022] However, depositing multiple layers directly onto a reflective core layer, such as an aluminum (Al) reflective core, can be difficult, and depositing multiple materials in multiple layers with nanoscale thicknesses can be challenging. Atomic layer deposition (ALD) is one method that works well for both, but ALD deposition has traditionally been costly and time-consuming. For example, because ALD essentially deposits materials at the atomic level, it can take a long time to deposit thick layers, such as layers with thicknesses greater than 500 nm, using an ALD process. As such, ALD is typically not preferred for depositing all layers in a multilayer structure. Due to cost and time constraints, ALD is typically reserved for depositing very thin layers, and layers applied by previous ALD methods have resulted in low-quality layers that may have insufficient coverage or high porosity, making 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 discovered that using ALD to deposit all layers of a multilayer structure provides layers with properties, such as surface area and pore volume, that allow a microlayer structure having three layers to perform similarly to a multilayer structure having significantly more layers. Specifically, embodiments disclosed herein use an ALD process to deposit a dense, non-porous metal and / or metal oxide layer onto a reflector (e.g., Al, etc.). The quality of the layers deposited by ALD allows for a three-layer OSC multilayer structure to have optical properties similar to five- and seven-layer OSC multilayer structures. Reducing the number of layers deposited in a multilayer structure can reduce manufacturing costs and time.

[0024] The multilayer structures described herein can be used to reflect wavelengths of visible light over a range of angles of incidence or viewing (e.g., hues from 0° to 120°). As used herein, the terms "electromagnetic waves," "electromagnetic radiation," and "light" refer interchangeably to various wavelengths of light incident on the multilayer structure, and it will be understood that such light can have wavelengths in the ultraviolet (UV), infrared (IR), and visible portions of the electromagnetic spectrum.

[0025] As used herein, "core layer" refers to reflective and non-reflective core layers, and the "core layer" may have any shape, including, but not limited to, flake, spherical, ovoid, etc. As used herein, "absorber layer" encompasses metallic and non-metallic absorber layers.

[0026] 1 , a multilayer structure 100 according to 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 multilayer structure 100 disclosed and described herein is comprised of three optical layers. These “optical layers” are layers that affect the optical properties of the multilayer structure 100, for example, layers made of reflective, dielectric, and absorber materials of sufficient thickness to affect the optical properties of the multilayer structure. As used herein, the term “optical layer” does not encompass thin barrier layers that do not affect the optical properties of the multilayer structure.

[0027] 2A-2C and 3, the effectiveness of different types of layers extending over the reflective core layer 110 in achieving desired hue levels in desired regions of the visible light spectrum plotted or depicted on the Lab color space is shown. FIG. 2A shows a ZnS dielectric layer 120a extending over the reflective core layer 110, FIG. 2B shows a Si semiconductor absorber layer 120b extending over the reflective core layer 110, and FIG. 2C shows an Fe2O3 dielectric layer 120c extending over the reflective core layer 110. Simulations of the reflectance from each multilayer structure shown in FIGS. 2A-2C were performed as a function of various thicknesses of the dielectric layer 120a, the semiconductor absorber layer 120b, and the dielectric layer 120c. The results of the simulations are plotted in the Lab color space (a) shown in FIG. 3. * b * 3. Each data point shown in FIG. 3 provides the saturation and hue for a particular thickness of the dielectric layer of the multilayer structure shown in FIG. 2A, the semiconductor absorber layer of the multilayer structure shown in FIG. 2B, or the dielectric layer of the multilayer structure shown in FIG. 2C. The saturation is

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[0028] Referring to Figures 4A-4C, saturation and hue are shown as a function of layer thickness. Specifically, Figure 4A graphically illustrates saturation and hue as a function of thickness for a ZnS dielectric layer extending over the Al reflective core layer shown in Figure 2A. Figure 4B illustrates saturation and hue as a function of thickness for a Si semiconductor absorber layer extending over the Al reflective core layer shown in Figure 2B. Figure 4C illustrates saturation and hue as a function of thickness for an Fe2O3 dielectric layer extending over the Al reflective core layer shown in Figure 2C. The dotted lines in Figures 4A-4C correspond to desired hue values ​​between 10° and 30° in the Lab color space. Figures 4A-4C demonstrate that higher saturation values ​​are achieved within the 10° to 30° hue range for multilayer structures having a dielectric layer extending over the reflective core layer. Again, it should be understood that the hue and saturation shown in Figures 4A-4C are for illustrative purposes and that multi-layer structures according to embodiments disclosed and described herein may have different hue and saturation values.

[0029] Referring again to FIG. 1 , a color-reflecting multilayer structure 100 according to an embodiment is shown. The multilayer structure 100 includes a core layer 110, a conformal dielectric layer 120 that encases the core layer 110, and a conformal absorber layer 130 that encases the conformal dielectric layer 120. As shown in FIG. 1 , the multilayer structure embodiments 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 a layer conforms to the size and shape of the layer on which it is deposited and encases (i.e., is present on all sides) the layer on which it is deposited. While FIG. 1 shows a rectangular structure, this is for illustrative purposes only; often, multilayer structures have asymmetric and non-uniform shapes. In embodiments, the multilayer structure may be spherical or ovoid. It should be understood that embodiments may also include multi-layer structures having a conformal absorber encapsulating a core layer and a conformal dielectric layer encapsulating the conformal absorber layer.

[0030] In an embodiment, the core layer 110 can have a thickness of 20 nm to 100 μm, for example, 50 nm to 80 μm, 75 nm to 60 μm, 100 nm to 40 μm, 125 nm to 20 μm, or 150 nm to 1 μm. In an embodiment, the core layer 110 can have a thickness of 50 nm to 10 μm, for example, 100 nm to 10 μm, 250 nm to 10 μm, 500 nm to 10 μm, 750 nm to 10 μm, 1μm~10μm, 2μm~10μm, 5μm~10μm, 8μm~10μm, 50nm~8μm, 100nm~8μm, 250nm~8μm, 500nm~8μm, 750nm~8μm, 1μm~8μm, 2μm~8μm, 5 μm~8μm, 50nm~5μm, 100nm~5μm, 250nm~5μm, 500nm~5μm, 750nm~5μm, 1μm~5μm, 2μm~5μm, 50nm~2μm, 100nm~2μm, 250nm~2μm, 50 The thickness may be 0 nm to 2 μm, 750 nm to 2 μm, 1 μm to 2 μm, 50 nm to 1 μm, 100 nm to 1 μm, 250 nm to 1 μm, 500 nm to 1 μm, 750 nm to 1 μm, 50 nm to 750 nm, 100 nm to 750 nm, 250 nm to 750 nm, 500 nm to 750 nm, 50 nm to 500 nm, 100 nm to 500 nm, 250 nm to 500 nm, 50 nm to 250 nm, 100 nm to 250 nm, or 50 nm to 100 nm.

[0031] In embodiments, the core layer 110 can be made from at least one of a "gray metal" material, such as Al, Ag, Pt, Sn, or a "colorful metal" material, such as Au, Cu, brass, bronze, TiN, Cr, stainless steel, or a combination thereof. In one or more embodiments, the core layer 110 can be made from an oxide, such as alumina (Al2O3), silica (SiO2), or a glass material. The core layer 110 can have a plate-like shape, or can be spherical or ovoid, as described above.

[0032] According to one or more embodiments, the conformal dielectric layer 120 has a thickness of 5 nm to 500 nm, e.g., 10 nm to 475 nm, 10 nm to 450 nm, 10 nm to 425 nm, 10 nm to 400 nm, 10 nm to 375 nm, 10 nm to 350 nm, 10 nm to 325 nm, or 10 nm to 300 nm. According to an embodiment, the conformal dielectric layer 120 may have a thickness of 5 nm to 300 nm, for example, 10 nm to 300 nm, 15 nm to 300 nm, 25 nm to 300 nm, 50 nm to 300 nm, 75 nm to 300 nm, 100 nm to 300 nm, 125 nm to 300 nm, 150 nm to 300 nm, 175 nm to 300 nm, 200 nm to 300 nm, 225 nm to 300 nm, 250 nm to 300 nm, 275 nm to 300 nm, 5 nm to 275 nm, 10 nm to 275nm, 15nm~275nm, 25nm~275nm, 50nm~275nm, 75nm~275nm, 100nm~275nm, 125nm~275nm, 150nm~275nm, 175nm~275nm, 200nm ~275nm, 225nm~275nm, 250nm~275nm, 5nm~250nm, 10nm~250nm, 15nm~250nm, 25nm~250nm, 50nm~250nm, 75nm~250nm, 100nm~25 0nm, 125nm~250nm, 150nm~250nm, 175nm~250nm, 200nm~250nm, 225nm~250nm, 5nm~225nm, 10nm~225nm, 15nm~225nm, 25nm~22 5nm, 50nm~225nm, 75nm~225nm, 100nm~225nm, 125nm~225nm, 150nm~225nm, 175nm~225nm, 200nm~225nm, 5nm~200nm, 10nm~20 0nm, 15nm~200nm, 25nm~200nm, 50nm~200nm, 75nm~200nm, 100nm~200nm, 125nm~200nm, 150nm~200nm, 175nm~200nm, 5nm~175 nm, 10nm~175nm, 15nm~175nm, 25nm~175nm, 50nm~175nm, 75nm~175nm, 100nm~175nm, 125nm~175nm, 150nm~175nm, 5nm~150nm,It can have a thickness of 10 nm to 150 nm, 15 nm to 150 nm, 25 nm to 150 nm, 50 nm to 150 nm, 75 nm to 150 nm, 100 nm to 150 nm, 125 nm to 150 nm, 5 nm to 100 nm, 10 nm to 100 nm, 15 nm to 100 nm, 25 nm to 100 nm, 50 nm to 100 nm, 75 nm to 100 nm, 5 nm to 75 nm, 10 nm to 75 nm, 15 nm to 75 nm, 25 nm to 75 nm, 50 nm to 75 nm, 5 nm to 50 nm, 10 nm to 50 nm, 15 nm to 50 nm, 25 nm to 50 nm, 5 nm to 25 nm, 10 nm to 25 nm, 15 nm to 25 nm, 5 nm to 15 nm, 10 nm to 15 nm, or 5 nm to 10 nm.

[0033] Conformal dielectric layer 120, in embodiments, is a high refractive index material such as TiO (including anatase, rutile, or amorphous TiO and mixtures thereof), ZnS, ZrO, HfO, FeO, or AlAs. In one or more embodiments, conformal dielectric layer 120 can be made of a high refractive index absorbing dielectric material such as FeO, PbS, GaAs, or InAs. In embodiments, conformal dielectric layer 120 can be made of a low refractive index material such as SiO, MgF, KBr, ZnO, or AlO. Conformal dielectric layer 120, in embodiments, can be deposited to encapsulate core layer 110 by CVD, PVD, wet chemical methods, or ALD.

[0034] 1, a conformal absorber layer 130 encases the conformal dielectric layer 120. The location of the conformal absorber layer 130 is selected to increase absorption of a targeted optical wavelength. For example, if a multilayer structure is configured to absorb electromagnetic radiation having wavelengths of 550 nm or less, but reflect electromagnetic radiation having wavelengths around 650 nm, such as visible light outside the 10°-30° hue, the absorber layer may be configured to reduce the electric field (|E|) at a wavelength of 550 nm by more than at a wavelength of 650 nm. 2) is smaller. Mathematically, this can be expressed as:

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[0035] 5 and the following discussion provide a method for calculating the thickness of a zero or near-zero electric field point at a given wavelength of light, according to an embodiment. For purposes of this specification, the term "near-zero" refers to a point where |E| 2 ≦10. s 1 illustrates a multilayer stack comprising a dielectric layer 4 having a total thickness "D", an incremental thickness "d", and a refractive index "n" on a substrate layer 2 having a thickness "D". The substrate layer 2 can be a core layer or a 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 a line 6 that is normal to the outer surface 5, and is reflected from the outer surface 5 at the same angle θ. The incident light is transmitted through the outer surface 5 and reflected into the dielectric layer 4 at an angle θ with respect to the line 6. F and the surface 3 of the base layer 2 is s In the case of a single dielectric layer, θ s =θ F The energy / electric field (E) can be expressed as E(z) when z=d. From Maxwell's equations, the electric field is, for s-polarized light,

number

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[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 calculation of the unknown parameters u(z) and v(z), where:

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[0037]

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[0038] In embodiments, the conformal absorber layer has a thickness that is 2 to 50 nm, 2 to 45 nm, 2 to 40 nm, 2 to 35 nm, 2 to 30 nm, or 2 to 25 nm. The conformal absorber layer 130 can have a thickness in an embodiment of 2 nm to 20 nm, e.g., 5 nm to 20 nm, 8 nm to 20 nm, 10 nm to 20 nm, 12 nm to 20 nm, 15 nm to 20 nm, 18 nm to 20 nm, 2 nm to 18 nm, 5 nm to 18 nm, 8 nm to 18 nm, 10 nm to 18 nm, 12 nm to 18 nm, 15 nm to 18 nm, 2 nm to 15 nm, 5 nm to 15 nm, 8 nm to 15 nm, 10 nm to 15 nm, 12 nm to 15 nm, 2 nm to 12 nm, 5 nm to 12 nm, 8 nm to 12 nm, 10 nm to 12 nm, 2 nm to 10 nm, 5 nm to 10 nm, 8 nm to 10 nm, 2 nm to 8 nm, 5 nm to 8 nm, or 2 nm to 5 nm.

[0039] In embodiments, the conformal absorber layer 130 may be made from a material selected from at least W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, ferric oxide, or combinations thereof. In one or more embodiments, the conformal absorber layer 130 is comprised of W. In embodiments, ALD is used to deposit the conformal absorber layer 130 because it allows for uniform deposition of material at a desired thickness. Other deposition methods have difficulty depositing uniform layers at thicknesses of 20 nm or less.

[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 thickness of 0.030 cm 3 / g or less, e.g., 0.025 cm 3 / g or less, 0.020cm 3 / g or less, or 0.015cm 3In an embodiment, the core layer 110, the conformal dielectric layer 120, and the conformal absorber layer 130 each have a pore volume of 0.010 cm / g or less. 3 / g or less, e.g., 0.009 cm 3 / g or less, 0.008cm 3 / g or less, 0.007cm 3 / g or less, 0.006cm 3 / g or less, 0.005cm 3 / g or less, 0.004cm 3 / g or less, 0.003cm 3 / g or less, 0.002cm 3 / g or less, 0.001cm 3 / g or less. It should be understood that in embodiments, one or more of core layer 110, conformal dielectric layer 120, and conformal absorber layer 130 can have the same pore volume, and in other embodiments, one or more of core layer 110, conformal dielectric layer 120, and conformal absorber layer 130 can 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, individually, is greater than or equal to 100 square meters per gram (m 2 / g) or less, for example, 90m 2 / g or less, 85m 2 / g or less, 80m 2 / g or less, 75m 2 / g or less, 70m 2 / g or less, 65μm or less, 60m 2 / g or less, 55m 2 / g or less, 50m 2 / g or less, 45m 2 / g or less, 45m 2 / g or less, 35m 2 / g or less, 30m 2 / g or less, 25m 2 / g or less, 20m 2 / g or less, or 15m 2In an embodiment, the surface area of ​​each of the core layer 110, the conformal dielectric layer 120, and the conformal absorber layer 130, individually, is less than 10 m 2 / g or less, e.g., 9m 2 / g or less, 8m 2 / g or less, 7m 2 / g or less, 6m 2 / g or less, 5m 2 / g or less, 4m 2 / g or less, 3m 2 / g or less, 2m 2 / g or less, or 1m 2 / g or less. Thus, in an embodiment, each layer has a thickness of 2 m 2 / g~10m 2 / g, 3m 2 / g~10m 2 / g, 3m 2 / g~8m 2 / g, 5m 2 / g~8m 2 / g, 1m 2 / g~3m 2 / g, 3m 2 / g~5m 2 / g, 2m 2 / g~3m 2 / g, 1m 2 / g~2m 2 / g, or 0.5m 2 / g~1m 2 / g, which is determined by collecting a full adsorption / desorption isotherm on the sample after degassing at 90°C for 1 hour and at 150°C for 3 hours. It should be understood that in embodiments, one or more of the core layer 110, the conformal dielectric layer 120, and the conformal absorber layer 130 can have the same surface area, and in other embodiments, one or more of the core layer 110, the conformal dielectric layer 120, and the conformal absorber layer 130 can have different surface areas.

[0042] The specific surface area (SSA) of the material was obtained by collecting isotherms using nitrogen physical adsorption at 76 K and fitting 13 points collected from P / P≈0.06 to 0.3 to the Brunauer-Emmett-Teller (BET) equation. Further adsorption points were collected at various P / P≈0.95, followed by desorption to P / P≈0.06. The total pore volume was determined by the volume of nitrogen adsorbed at P / P≈0.95, and the average pore diameter was calculated using the Barrett-Joyner-Halenda (BJH) method.

[0043] In an embodiment, the multilayer structure has a D 50 The amount of adsorbed gas that will build one monolayer on the surface can be calculated from the measured isotherm. Multiplying the amount of molecules in this monolayer by the space required for one molecule gives the BET D 50 Given this BET D 50is 1 μm to 500 μm, for example, 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 ~500μm, 400μm~500μm, 450μm~500μm, 5μm~450μm, 10μm~450μm, 20μm~450μm , 25μm~450μm, 50μm~450μm, 100μm~450μm, 150μm~450μm, 200μm~450μm, 250μm m~450μm, 300μm~450μm, 350μm~450μm, 400μm~450μm, 5μm~400μm, 10μm~400 μm, 20μm~400μm, 25μm~400μm, 50μm~400μm, 100μm~400μm, 150μm~400μm, 200 μm~400μm, 250μm~400μm, 300μm~400μm, 350μm~400μm, 5μm~350μm, 10μm~35 0μm, 20μm~350μm, 25μm~350μm, 50μm~350μm, 100μm~350μm, 150μm~350μm, 20 0μm~350μm, 250μm~350μm, 300μm~350μm, 5μm~300μm, 10μm~300μm, 20μm~30 0μm, 25μm~300μm, 50μm~300μm, 100μm~300μm, 150μm~300μm, 200μm~300μm, 2 50μm~300μm, 5μm~250μm, 10μm~250μm, 20μm~250μm, 25μm~250μm, 50μm~250 μm, 100μm~250μm, 150μm~250μm, 200μm~250μm, 5μm~200μm, 10μm~200μm, 20μm m~200μm, 25μm~200μm, 50μm~200μm, 100μm~200μm, 150μm~200μm, 5μm~150μm m, 10μm~150μm, 20μm~150μm, 25μm~150μm, 50μm~150μm, 100μm~150μm, 5μm~1 00μm, 10μm~100μm, 20μm~100μm, 25μm~100μm, 50μm~100μm, 5μm~50μm, 10μm~ 50μm, 20μm~50μm, 25μm~50μm, 5μm~25μm, 10μm~25μm, 20μm~25μm, 5μm~20μm,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, when measured by electron microscopy (TEM, SEM) based on a large number of flakes (both cross-sections and surfaces are measured), is 1 to 100, for example, 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] The embodiments of the multilayer structure 100 described above have a hue shift in the Lab color space when viewed at an angle between 0° and 45° of less than 30°, 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 includes a reflective core layer 110 made of Al, a conformal dielectric layer 120 deposited by ALD and made of TiO, where the conformal dielectric layer 120 encapsulates the reflective core layer 110, and a conformal metallic absorber layer 130 deposited by ALD and made of W, where the conformal metallic absorber layer 130 encapsulates the conformal dielectric layer 120.

[0047] In one or more embodiments, the multilayer structure 100 includes a reflective core layer 110 made of Al, a conformal dielectric layer 120 deposited by ALD and made of FeO, where the conformal dielectric layer 120 encapsulates the reflective core layer 110, and a conformal metallic absorber layer 130 deposited by ALD and made of W, where the conformal metallic absorber layer 130 encapsulates the conformal dielectric layer 120.

[0048] The multilayer structures of the embodiments disclosed herein can be used as pigments (e.g., paint pigments in paints used to paint objects) or as continuous structures 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 paint that exhibits omnidirectional structural color. Additionally, other additives may be added to the multilayer structure to aid in the compatibility of the multilayer structure in paint systems. Exemplary compatibility-enhancing additives include silane surface treatments that coat the exterior of the multilayer structure and improve the compatibility of the multilayer structure in paint systems. Such paint systems or films can be used on any article, including automobiles.

[0049] As mentioned herein, at least one of the metal or metal oxide layers (e.g., a conformal dielectric layer and a conformal absorber layer, etc.) may be deposited by ALD. Embodiments of ALD processes for depositing these layers are described in more detail below.

[0050] Furthermore, the use of ALD processes allows for the deposition of multiple layers with optical precision and large differences in material properties (such as the dielectric versus metallic materials mentioned above). Furthermore, ALD processes enable the fabrication of multilayer structures with high density, low porosity, and complete layer coverage with nanometer-scale precision. Furthermore, the deposition precision and non-destructive nature of ALD minimizes the impact on existing, weak layers (e.g., Al core layers). Such results are difficult or costly to achieve with other processes.

[0051] A first embodiment encompasses a color-reflecting multilayer structure of three optical layers, including a core layer, a conformal dielectric layer encapsulating the core layer, and a conformal absorber layer encapsulating the conformal dielectric layer.

[0052] A second aspect encompasses the multilayer structure according to the first aspect, wherein the multilayer structure, when exposed to broadband electromagnetic radiation, reflects a single narrow band of visible light, the single narrow band of visible light comprising a color shift of the single narrow band of visible light, measured in Lab color space, of less than 30° when the multilayer structure is exposed to broadband electromagnetic radiation and observed from an angle of 0° to 45° relative to a direction normal to an outer surface of the multilayer structure.

[0053] A third embodiment includes the multilayer structure of the first or second embodiment, wherein the core layer is formed from Al, Ag, Pt, Sn, Au, Cu, brass, bronze, stainless steel, TiN, Cr, Al2O3, SiO2, glass, or a combination thereof.

[0054] A fourth aspect includes the multilayer structure according to any one of the first to third aspects, wherein the core layer has a thickness of 20 nm to 100 μm.

[0055] A fifth aspect includes the multilayer structure according to any one of the first to fourth aspects, wherein the conformal dielectric layer is formed from TiO2, ZnS, ZrO2, HfO2, Fe3O4, AlAs, Fe2O3, PbS, GaAs, InAs, SiO2, MgF2, KBr, ZnO, Al2O3, and combinations thereof.

[0056] A sixth aspect encompasses the multilayer structure according to any one of the first to fifth aspects, wherein the conformal dielectric layer has a thickness of 5 nm to 500 nm.

[0057] A seventh aspect includes a multilayer structure according to any one of the first to sixth aspects, wherein the conformal absorber layer is formed from W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, ferric oxide, or a combination thereof.

[0058] An eighth aspect encompasses the multilayer structure according to any one of the first to seventh aspects, wherein the conformal absorber layer has a thickness of 2 nm to 50 nm.

[0059] A ninth aspect includes a multilayer structure according to any one of the first to eighth aspects, wherein the core layer is formed from Al, the conformal dielectric layer is formed from TiO, and the conformal absorber layer is formed from W.

[0060] A tenth aspect includes the multilayer structure according to any one of the first to eighth aspects, wherein the core layer is formed from Al, the conformal dielectric layer is formed from Fe2O3, and the conformal absorber layer is formed from W.

[0061] An eleventh aspect is a multilayer structure according to any one of the first to tenth aspects, wherein each of the core layer, the conformal dielectric layer and the conformal absorber layer has a thickness of 0.030 cm 3 The present invention encompasses multi-layer structures each having a pore volume of 0.1 to 1.0 μm / g or less.

[0062] A twelfth aspect is a multilayer 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 is 0.005 cm 3 The present invention encompasses multi-layer structures each having a pore volume of 1 / g or less.

[0063] A thirteenth aspect is a multilayer 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 is 100 mm thick. 2 The present invention encompasses multi-layer structures each having a surface area of ​​0.15 μm / g or less.

[0064] A fourteenth aspect is a multilayer 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 is 5 mm thick. 2 The present invention encompasses multi-layer structures each having a surface area of ​​0.15 μm / g or less.

[0065] A fifteenth aspect is a multilayer structure according to any one of the first to fourteenth aspects, wherein the multilayer structure has a thickness of 1 μm or more and 500 μm or less. 50 The present invention includes a multi-layer structure having a diameter.

[0066] A sixteenth aspect encompasses the multilayer structure according to any one of the first to fifteenth aspects, wherein the multilayer structure has an aspect ratio of 1 or more and 100 or less.

[0067] A seventeenth aspect encompasses a method for forming the multilayer structure of any one of the first to sixteenth aspects, comprising 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.

[0068] An eighteenth aspect includes a method for forming the multilayer structure of any one of the first to sixteenth aspects, comprising depositing a conformal dielectric layer by ALD on a core layer, and depositing a conformal absorber layer by ALD on the conformal dielectric layer.

[0069] A nineteenth embodiment encompasses a coating system comprising a binder and the multilayer structure of any one of the first to sixteenth embodiments.

[0070] A twentieth embodiment includes a motor vehicle equipped with the paint system of the nineteenth embodiment.

[0071] It should be noted that the terms "substantially" and "about" may be used in this disclosure to express the inherent degree of uncertainty that may result from any quantitative comparison, value, measurement, or other representation. These terms are also used in this disclosure to express the extent to which a quantitative representation may vary from the stated basis without resulting in a change in the basic functionality of the subject matter under discussion. [Example]

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

[0073] Example 1

[0074] The multilayer structure was formed by an ALD process in which each layer in the three-layer multilayer structure was deposited individually as a smoothing layer.

[0075] Example 2

[0076] The TiO2 dielectric layer deposited by the ALD process of Example 1 was compared with a TiO2 dielectric layer formed by a wet chemical method.

[0077] The pigment was suspended in isopropyl alcohol (IPA) in a flask at 40°C, and a solution of titanium ethoxide dissolved in IPA was titrated at a constant rate for 2.5 hours. Simultaneously, deionized water diluted with IPA was measured. After titration, the suspension was stirred for an additional 30 minutes. The mixture was allowed to cool to room temperature, then filtered, washed with IPA, and dried at 100°C for 24 hours. The collected product was then sintered at 300-500°C for 2-6 hours.

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

[0079] Example 3

[0080] In this example, the effect of the thickness of the tungsten metal absorber layer and the TiO dielectric layer was investigated. Figure 6A shows four samples fabricated according to the ALD process of Example 1, except 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 had an Al reflective core layer and a 50 nm thick TiO dielectric layer. As shown in Figure 6A, as the thickness of the tungsten layer increased, the reflectivity curve shifted slightly to the left (toward lower wavelengths) and became more reflective.

[0081] Figure 6B shows four samples fabricated according to the ALD process of Example 1, except 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 had an Al reflective core layer and a 5 nm thick tungsten metal absorber layer. As shown in Figure 6B, as the thickness of the titanium dioxide layer increased, the reflectivity curve shifted slightly to the left (toward lower wavelengths). However, each of the samples performed significantly better than the seven-layer structure formed by vacuum deposition.

[0082] Example 4

[0083] This example compares the density, surface area, and pore volume of multilayer structures fabricated according to the ALD process of 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 the ALD and wet chemical methods were the same, but the surface area of ​​the multilayer structures was much smaller using the ALD method.

[0084] [Table 1]

[0085] The density of a pigment is the ratio of the mass of a pigment sample to its volume, including the contribution of interparticle void volume. To measure it, a glass cylinder with a specific volume was used, and a known mass of pigment was introduced into the cylinder. The volume was estimated by adding deionized water to the cylinder until the water reached the volume line of the cylinder. The volume of the water was determined by measuring the mass of the deionized water added. The sample volume was calculated by subtracting the volume of the water from the total volume of the cylinder. To determine density, replicate experiments were performed. Full adsorption / desorption isotherms were collected for samples degassed at 90°C for 1 hour and then at 150°C for 3 hours. Isotherms were then collected using nitrogen physisorption at 76 K. The specific surface area (SSA) of the material was obtained by fitting 13 points collected from P / P≈0.06 to 0.3 to the Brunauer-Emmett-Teller (BET) equation. Further adsorption points were collected at various P / P0 up to P / P0 ≈ 0.95 followed by desorption up to P / P0 ≈ 0.06, the total pore volume was determined by the volume of nitrogen adsorbed at P / P0 0.95 and the average pore diameter was calculated using the Barrett Joyner Halenda (BJH) method.

[0086] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, this specification is intended to cover modifications and variations of the various embodiments described herein, provided such modifications and variations come within the scope of the appended claims and their equivalents.

Claims

1. A multilayer structure that reflects color, The core layer, A conformal dielectric layer enclosing the core layer, A conformal absorber layer enclosing the conformal dielectric layer, A multilayer structure comprising three optical layers.

2. The multilayer structure according to claim 1, wherein the multilayer structure reflects a single narrowband of visible light when exposed to broadband electromagnetic radiation, and the multilayer structure has a hue shift of the single narrowband of visible light that is less than 30° as measured in Lab color space when the multilayer structure is exposed to broadband electromagnetic radiation and observed from an angle of 0° to 45° with respect to the direction perpendicular to the outer surface of the multilayer structure.

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

4. The multilayer structure according to claim 1, wherein the core layer has a thickness of 20 nm to 100 μm.

5. The conformable dielectric layer is 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 The multilayer structure according to claim 1, formed from or a combination thereof.

6. The multilayer structure according to claim 1, wherein the conformal dielectric layer has a thickness of 5 nm to 500 nm.

7. The multilayer structure according to claim 1, wherein the conformal absorber layer is formed from W, Cr, Ge, Ni, stainless steel, Pd, Ti, Si, V, TiN, Co, Mo, Nb, ferric oxide, or a combination thereof.

8. The multilayer structure according to claim 1, wherein the conformal absorber layer has a thickness of 2 nm to 50 nm.

9. The core layer is formed from Al, The conformal dielectric layer is TiO ２ Formed from, The conformal absorber layer is formed from W. The multilayer structure according to claim 1.

10. The core layer is formed from Al, The conformal dielectric layer is Fe ２ O ３ Formed from, The conformal absorber layer is formed from W. The multilayer structure according to claim 1.

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

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

13. The multilayer structure according to claim 1, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer individually has a surface area of ​​100 m² or less per gram of each of the core layer, the conformal dielectric layer, and the conformal absorber layer.

14. The multilayer structure according to claim 1, wherein each of the core layer, the conformal dielectric layer, and the conformal absorber layer individually has a surface area of ​​5 m² or less per gram of each of the core layer, the conformal dielectric layer, and the conformal absorber layer.

15. The multilayer structure is D, which is 1 μm to 500 μm in thickness. ５０ A multilayer structure according to claim 1, having a diameter.

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

17. A method for forming a multilayer structure according to claim 1, Depositing the conformal dielectric layer on the core layer by CVD or ALD, A method comprising depositing the conformal absorber layer on the conformal dielectric layer using ALD.

18. A method for forming a multilayer structure according to claim 1, The conformal dielectric layer is deposited on the core layer by ALD, A method comprising depositing the conformal absorber layer on the conformal dielectric layer using ALD.

19. A coating system comprising a binder and a multilayer structure according to any one of claims 1 to 16.

20. An automobile equipped with the painting system described in claim 19.

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