Omnidirectional high chroma red structural color with a combination of a metallic absorber layer and a dielectric absorber layer

Abstract

This invention relates to an omnidirectional high-chromaticity red structural pigment having a combination of a metal absorber layer and a dielectric absorber layer. An omnidirectional high-chromaticity red structural pigment is provided. The omnidirectional structural pigment is in the form of a multilayer stack having a reflective core layer, a metal absorber layer extending across the reflective core layer, and a dielectric absorber layer extending across the metal absorber layer. The multilayer stack reflects single-band visible light with a hue between 0 and 40°, and preferably between 10 and 30°, on the a*b*Lab color map. Furthermore, when viewed from all angles between 0 and 45° perpendicular to the outer surface of the multilayer stack, the single-band visible light exhibits a hue shift of less than 30° on the a*b*Lab color map.

Description

[0001] This application is a divisional application of the invention patent application filed on June 7, 2016, with application number 201610395759.3 and invention title "Omnidirectional High Chromaticity Red Structural Pigment Having a Combination of Metal Absorber Layer and Dielectric Absorber Layer".

[0002] Cross-references to related applications

[0003] This application is a continuation-in-part (CIP) of U.S. Patent Application No. 14 / 607,933, filed January 28, 2015. U.S. Patent Application No. 14 / 607,933 is a CIP of U.S. Patent Application No. 14 / 471,834, filed August 28, 2014. U.S. Patent Application No. 14 / 471,834 is a CIP of U.S. Patent Application No. 14 / 460,511, filed August 15, 2014. U.S. Patent Application No. 14 / 460,511 is a CIP of U.S. Patent Application No. 14 / 242,429, filed April 1, 2014. U.S. Patent Application No. 429 is a CIP of U.S. Patent Application No. 14 / 138,499, filed December 23, 2013; U.S. Patent Application No. 14 / 138,499 is a CIP of U.S. Patent Application No. 13 / 913,402, filed June 8, 2013; U.S. Patent Application No. 13 / 913,402 is a CIP of U.S. Patent Application No. 13 / 760,699, filed February 6, 2013; and U.S. Patent Application No. 13 / 760,699 is a CIP of U.S. Patent Application No. 13 / 572,071, filed August 10, 2012. The entire contents of all of the above applications are incorporated herein by reference. Invention Field

[0004] The present invention relates to a multilayer stacked structure that exhibits a high-chromaticity red color with minimal or insignificant color shift when exposed to broadband electromagnetic radiation and viewed from different angles. Background Technology

[0005] Pigments made of multilayer structures are known. Furthermore, pigments exhibiting or providing high chromaticity omnidirectional structural colors are also known. However, such prior art pigments require up to 39 thin film layers to achieve the desired color properties.

[0006] It should be understood that the cost associated with the fabrication of multilayer pigments is proportional to the number of layers required. Thus, the cost associated with fabricating high-chromaticity omnidirectional structural colors using multilayer dielectric material stacks can be prohibitively high. Therefore, high-chromaticity omnidirectional structural colorants requiring a minimum number of thin film layers are desirable.

[0007] In addition to the above, it should be understood that the design of red pigments faces additional challenges compared to pigments of other colors (such as blue, green, etc.). In particular, controlling the angular independence of red is difficult because it requires thicker dielectric layers, which in turn leads to high harmonic design, meaning the presence of second and possibly third harmonics is unavoidable. Furthermore, the hue space of dark red is very narrow. Thus, multilayer stacks of red pigments exhibit high angular variance.

[0008] For the reasons mentioned above, a high-chromaticity red omnidirectional structural color pigment with the fewest layers would be desirable. Summary of the Invention

[0009] An omnidirectional, high-chromaticity red structural color pigment is provided. This omnidirectional structural color pigment is in the form of a multilayer stack having a reflective core layer, a metal absorber layer extending across the reflective core layer, and a dielectric absorber layer extending across the metal absorber layer. The multilayer stack reflects single-band visible light with a hue between 0-40°, and preferably between 10-30°, on the a*b*Lab color map. Furthermore, when viewed from all angles between 0-45° perpendicular to the outer surface of the multilayer stack, this single-band visible light exhibits a hue shift of less than 30° on the a*b*Lab color map, thereby providing a color shift that is not significant to the human eye.

[0010] The reflective core layer has a thickness between 50 and 200 nanometers (nm) (inclusive) and can be made of reflective metals such as aluminum (Al), silver (Ag), platinum (Pt), tin (Sn), and combinations thereof. The reflective core layer can also be made of colored metals such as gold (Au), copper (Cu), brass, bronze, etc.

[0011] The metal absorber layer may have a thickness between 5 and 500 nm (inclusive) and may be made of materials such as colored metals, such as copper (Cu), gold (Au), bronze (Cu-Zn alloy), brass (Cu-Sn alloy), amorphous silicon (Si), or colored nitride materials (such as titanium nitride (TiN)). The dielectric absorber layer may have a thickness between 5 and 500 nm (inclusive) and may be made of a dielectric material, such as, but not limited to, iron oxide (Fe2O3).

[0012] The reflective core layer, the metal absorber layer, and / or the dielectric absorber layer can be dry-deposited layers. However, the dielectric absorber layer can be wet-deposited layers. Furthermore, the reflective core layer can be a central reflective core layer, and the metal absorber layers are a pair of metal absorber layers extending across opposite sides of the central reflective core layer, i.e., the central reflective core layer is sandwiched between the pair of metal absorber layers. Moreover, the dielectric absorber layers can be a pair of dielectric absorber layers, such that the central reflective core layer and the pair of metal absorber layers are sandwiched between the pair of dielectric absorber layers.

[0013] A method for preparing such an omnidirectional high-chromaticity red structural pigment includes: fabricating a multilayer stack by dry deposition of a reflective core layer, dry deposition of a metal absorber layer extending across the reflective core layer, and dry or wet deposition of a dielectric absorber layer extending across the metal absorber layer. In this way, the hybrid manufacturing method can be used to produce omnidirectional high-chromaticity red structural pigments suitable for use in pigments, coatings, etc. Brief description of the attached figures

[0014] Figure 1 This is a schematic illustration of an omnidirectional structural color multilayer stack made of a dielectric layer, a selective absorption layer (SAL), and a reflector layer;

[0015] Figure 2A This is a schematic illustration of the zero or near-zero electric field point within a ZnS dielectric layer exposed to electromagnetic radiation (EMR) at a wavelength of 500 nm.

[0016] Figure 2B When exposed to EMR at wavelengths of 300, 400, 500, 600, and 700 nm Figure 2A The square of the absolute value of the electric field of the ZnS dielectric layer shown (|E|) 2 A diagram showing the thickness;

[0017] Figure 3 A schematic illustration of a dielectric layer that extends over a substrate or reflector layer and is exposed to electromagnetic radiation at an angle θ relative to the normal direction of the outer surface of the dielectric layer.

[0018] Figure 4 This is a schematic illustration of a ZnS dielectric layer with a Cr absorber layer located at a zero or near-zero electric field point within the ZnS dielectric layer for incident EMR at a wavelength of 434 nm.

[0019] Figure 5 For multilayer stacks without Cr absorber layers exposed to white light (e.g.) Figure 2A ) and multilayer stacks with Cr absorber layers (e.g. Figure 4 A graph showing the percentage reflectance of the reflected EMR wavelength.

[0020] Figure 6A For a ZnS dielectric layer extending above an Al reflector layer (e.g. Figure 2A The diagram shows the first and second harmonics as exhibited.

[0021] Figure 6B A Cr absorber layer is added within the ZnS dielectric layer to the ZnS dielectric layer, which has a transverse extension across the Al reflector layer (thus absorbing the Cr absorber layer). Figure 6A A graph showing the percentage reflectivity of the multilayer stack of the second harmonic (as shown) against the reflected EMR wavelength;

[0022] Figure 6C A Cr absorber layer is added within the ZnS dielectric layer to the ZnS dielectric layer, which has a transverse extension across the Al reflector layer (thus absorbing the Cr absorber layer). Figure 6A A graph showing the percentage reflectivity of the multilayer stack of the first harmonic (as shown) against the reflected EMR wavelength.

[0023] Figure 7A A graph showing the square value of the electric field as a function of the dielectric layer thickness, indicating the electric field angle dependence of the Cr absorber layer when exposed to incident light at 0 and 45 degrees.

[0024] Figure 7B This is a graph showing the percentage absorptivity of the Cr absorber layer versus the reflected EMR wavelength when exposed to white light at angles of 0° and 45° relative to the normal to the outer surface (0° being perpendicular to the surface).

[0025] Figure 8A This is a schematic illustration of a red omnidirectional structural color multilayer stack based on one aspect of the present invention;

[0026] Figure 8B White light is exposed at incident angles of 0° and 45°. Figure 8A When the multi-layer stacked body shown is in Figure 8A The graph shows the percentage absorption of the Cu absorber layer versus the reflected EMR wavelength.

[0027] Figure 9 A comparison of calculated / simulated and experimental data on the percentage reflectance of a red omnidirectional structural color multilayer stack exposed to white light at an incident angle of 0° for proof of concept, versus the reflected EMR wavelength.

[0028] Figure 10 A graph illustrating the percentage reflectance of an omnidirectional structural color multilayer stack against wavelength according to one aspect of the present invention;

[0029] Figure 11 A graph illustrating the percentage reflectance of an omnidirectional structural color multilayer stack against wavelength according to one aspect of the present invention;

[0030] Figure 12 A diagram showing a portion of the a*b* color mapping using the CIELAB (Lab) color space, in which the chromaticity and hue shift of a conventional paint are compared with that of a paint prepared from a pigment according to one aspect of the present invention (sample (b)).

[0031] Figure 13 This is a schematic illustration of a red omnidirectional structural color multilayer stack as disclosed in this article;

[0032] Figure 14 yes Figure 13 The graph shows the percentage reflectance of each aspect against the wavelength.

[0033] Figure 15 yes Figure 13 The graph shows the percentage absorption rate of each aspect versus wavelength.

[0034] Figure 16 yes Figure 13 The graph shows the percentage reflectance of each aspect against the wavelength versus the viewing angle.

[0035] Figure 17 yes Figure 13 The diagram shows the relationship between chromaticity and hue of the aspects shown and the viewing angle.

[0036] Figure 18 It is by Figure 13 The illustration shows the color reflected from the aspect relative to the a*b*Lab color map; and

[0037] Figure 19 This is an illustrative description of a method for manufacturing an omnidirectional red structural color multilayer stack, based on one aspect of the method disclosed herein. Detailed Implementation

[0038] An omnidirectional high-chromaticity red structural pigment is provided. The omnidirectional high-chromaticity red structural pigment is in the form of a multilayer stack, which has a reflective core layer, a metal absorber layer, and a dielectric absorber layer. The metal absorber layer extends across the reflective core layer and, in some cases, directly abuts against the reflective core layer or is located on top of the reflective core layer. The dielectric absorber layer extends across the metal absorber layer and, in some cases, directly abuts against the metal absorber layer or is located on top of the metal absorber layer. The multilayer stack can be a symmetrical stack, i.e., the reflective core layer is a central reflective core layer constrained by a pair of metal absorber layers, and the pair of metal absorber layers is constrained by a pair of dielectric absorber layers.

[0039] The multilayer stack reflects a single-band visible light of red color, which has a hue between 0-40°, preferably between 10-30°, on the a*b*Lab color map. Furthermore, when the multilayer stack is viewed from all angles between 0-45° perpendicular to its outer surface, the hue shift of this single-band visible light on the a*b*Lab color map is less than 30°, preferably less than 20°, and more preferably less than 10°. Thus, the hue shift of the reflected single-band visible light can be within the 0-40° region and / or the 10-30° region on the a*b*Lab map.

[0040] The reflective core layer can be a dry-deposited layer with a thickness between 50 and 200 nm (inclusive). The term "dry-deposited" refers to dry deposition processes such as physical vapor deposition (PVD) including electron beam deposition, sputtering, chemical vapor deposition (CVD), and plasma-assisted CVD. In some cases, the reflective core layer is made of a reflective metal (e.g., Al, Ag, Pt, Sn, and combinations thereof). In other cases, the reflective core layer is made of a colored metal (e.g., Au, Cu, brass, bronze, and combinations thereof). It should be understood that the terms "brass" and "bronze" refer to copper-zinc alloys and copper-tin alloys, respectively, as known to those skilled in the art.

[0041] The metal absorber layer can also be a dry-deposited layer deposited on the reflective core layer. Alternatively, the reflective core layer can be deposited on the metal absorber layer. The metal absorber layer can have a thickness between 5 and 500 nm (inclusive) and can be made of colored metals (e.g., Cu, bronze, brass) or materials such as amorphous silicon (Si), germanium (Ge), TiN, etc.). It should be understood that, for the purposes of this invention, the term "metal absorber layer" includes materials that are not typically considered metals, such as amorphous Si, Ge, TiN, etc.

[0042] The dielectric absorber layer can be a dry-deposited layer or a wet-deposited layer deposited on a metal absorber layer. Alternatively, the metal absorber layer can be deposited on the dielectric absorber layer. The dielectric absorber layer can have a thickness between 5 and 500 nm (inclusive) and can be made of a dielectric material (e.g., iron oxide (Fe2O3)). Furthermore, the term "wet-deposited" refers to a wet deposition process, such as dissolution gel deposition, spin coating, or wet chemical deposition.

[0043] The overall thickness of the multilayer stack can be less than 3 micrometers, preferably less than 2 micrometers, more preferably less than 1.5 micrometers, and even more preferably less than or equal to 1.0 micrometers. In addition, the multilayer stack has a total number of layers of less than or equal to 9, preferably less than or equal to 7, and more preferably less than or equal to 5.

[0044] refer to Figure 1 The figure illustrates a design in which a lower reflector layer (RL) has a first dielectric material layer DL1 extending across the reflector layer and a selective absorption layer SAL extending across the DL1 layer. Alternatively, another DL1 layer may or may not be provided, and it may or may not extend across the selective absorption layer. The figure also illustrates the reflection or selective absorption of all incident electromagnetic radiation by this multilayer structure.

[0045] As in Figure 1 As explained, such a design corresponds to different approaches used for designing and manufacturing the desired multilayer stack. In particular, the thickness of the zero-energy point or near-zero-energy point for the dielectric layer is used and discussed below.

[0046] For example, Figure 2A This is a schematic illustration of a ZnS dielectric layer extending across an Al reflector core. The ZnS dielectric layer has a total thickness of 143 nm, and for incident electromagnetic radiation at a wavelength of 500 nm, a zero-energy point or near-zero energy point exists at 77 nm. In other words, for incident electromagnetic radiation (EMR) at a wavelength of 500 nm, the ZnS dielectric layer exhibits a zero-field or near-zero electric field at a distance of 77 nm from the Al reflector layer. Furthermore, Figure 2B A diagram is provided illustrating the energy field across the ZnS dielectric layer for several different incident EMR wavelengths. As shown in the diagram, for a wavelength of 500 nm, the dielectric layer has a zero electric field at a thickness of 77 nm, but for EMR wavelengths of 300, 400, 600, and 700 nm, it has a non-zero electric field at a thickness of 77 nm.

[0047] Calculations for zero or near-zero electric field points. Figure 3 This describes dielectric layer 4 with a total thickness "D", incremental thickness "d", and refractive index "n", located at a point with a refractive index n. s The incident light is incident on the outer surface 5 of the dielectric layer 4 at an angle θ relative to the line 6 perpendicular 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 is reflected from the line 6 at an angle θ. F It enters dielectric layer 4 and at an angle θ s The surface 3 of the substrate layer 2 is irradiated.

[0048] For a single dielectric layer, θ s =θ F Furthermore, when z = d, the energy / electric field (E) can be expressed as E(z). According to Maxwell's equations, for s-polarization, the electric field can be expressed as:

[0049]

[0050] Furthermore, p-polarization can be expressed as:

[0051]

[0052] in And λ is the desired wavelength to be reflected. Furthermore, α = n s sin θ s Where “s” corresponds to Figure 5 The substrate in, and Let be the dielectric constant of the layer as a function of z. Thus, for s-polarization...

[0053] |E(d)| 2 =|u(z)| 2 exp(2ikαy)| z = d (3)

[0054] And for p-polarization

[0055]

[0056] It should be understood that the variation of the electric field along the Z direction of dielectric layer 4 can be estimated by calculating the unknown parameters u(z) and v(z), which can be shown as follows:

[0057]

[0058] Naturally, "i" is the square root of -1. Using the boundary condition u| z＝0 =1,v| z＝0 =q s And the following relationship:

[0059] For s-polarization, q s =n s cos θ s (6)

[0060] For p-polarization, q s =n s / cos θ s (7)

[0061] For s-polarization, q = n cos θ F (8)

[0062] For p-polarization, q = n / cos θ F (9)

[0063]

[0064] u(z) and v(z) can be expressed as:

[0065]

[0066] and

[0067]

[0068] Therefore, for s-polarization:

[0069]

[0070] And for p-polarization:

[0071]

[0072] in:

[0073] α=n s sin θ s =n sin θ F (15)

[0074]

[0075] and

[0076]

[0077] Therefore, for θ F The simple cases are 0 or perpendicular incidence. And α = 0:

[0078] s-polarized |E(d)| 2 =p-polarized It allows the solution of the thickness "d", which is the location or point where the electric field is zero within the dielectric layer.

[0079] Now for reference Figure 4 Equation 19 is used to calculate the effect of exposure to EMR at a wavelength of 434 nm. Figure 2AThe diagram shows a zero or near-zero electric field point in the ZnS dielectric layer. This zero or near-zero electric field point is calculated to be 70 nm (or 77 nm for a 500 nm wavelength). Furthermore, a 15 nm thick Cr absorber layer is inserted at a thickness of 70 nm from the Al reflector core layer to provide a zero or near-zero electric field ZnS-Cr interface. This inventive structure allows light with a wavelength of 434 nm to pass through the Cr-ZnS interface, but absorbs light with a wavelength other than 434 nm. In other words, the Cr-ZnS interface has a zero or near-zero electric field for light with a wavelength of 434 nm, and therefore 434 nm light passes through this interface. However, the Cr-ZnS interface does not have a zero or near-zero electric field for light with a wavelength other than 434 nm, and therefore, such light is absorbed by the Cr absorber layer and / or the Cr-ZnS interface and is not reflected by the Al reflector layer.

[0080] It should be understood that some percentage of the light expected in the 434nm + / -10nm range will pass through the Cr-ZnS interface. However, it should also be understood that such narrow-band reflected light, such as 434 + / -10nm, will still provide a dazzling structural color to the human eye.

[0081] exist Figure 5 Chinese explanation Figure 4 The results for the Cr absorber layer in the multilayer stack are shown, where the percentage reflectance is shown in relation to the reflected EMR wavelength. As indicated by the dashed line, it corresponds to the... Figure 4 The ZnS dielectric layer shown without a Cr absorber layer exhibits a narrow reflection peak at approximately 400 nm, but a much wider peak at approximately 550+ nm. Furthermore, significant amounts of reflected light remain in the 500 nm wavelength region. Thus, a double peak exists to prevent the multilayer stack from exhibiting or displaying structural color.

[0082] In comparison, Figure 5 The solid line in the middle corresponds to the line in the middle. Figure 4 The structure with a Cr absorber layer is shown in the figure. As illustrated, a sharp peak exists at approximately 434 nm, and the Cr absorber layer provides a sharp decrease in reflectivity for wavelengths greater than 434 nm. It should be understood that the sharp peak, represented by the solid line, appears visually as a bright / structural color. Furthermore, Figure 5 It describes the measurement of the width of the reflection peak or band, that is, the width of the band is determined at 50% reflectivity at the maximum reflection wavelength (which is also known as half-width (FWHM)).

[0083] Regarding Figure 4The omnidirectional behavior of the multilayer structure shown can be designed or set such that the thickness of the ZnS dielectric layer provides only the first harmonic of the reflected light. It should be understood that this is sufficient for the "blue" color; however, the generation of the "red" color requires other conditions. For example, controlling the angular independence of the red color is difficult because a thicker dielectric layer is required, which in turn leads to a high harmonic design, meaning the presence of the second harmonic and possibly the third harmonic is unavoidable. Furthermore, the dark red color hue space is very narrow. Thus, the red multilayer stack exhibits high angular dispersion.

[0084] To overcome the high angular dispersion of red color, this application discloses a unique and novel design / structure that provides an angle-independent red color. For example, Figure 6A This illustrates a dielectric layer exhibiting first and second harmonics for incident white light when viewed from 0° and 45° relative to the normal to the outer surface. As illustrated, the thickness of the dielectric layer provides low angle dependence (small Δλ). c However, such a multi-layered stack has a combination of blue (first harmonic) and red (second harmonic) colors, and therefore is not suitable for the desired "red only" color. Therefore, a concept / structure using absorber layers to absorb the unwanted harmonic series has been developed. Figure 6A It also explains that for the given reflection peak, the center wavelength (λ) of the reflection band... c Examples of the position of the center wavelength, and the dispersion or shift (Δλ) of the center wavelength when the sample is viewed from 0 and 45°. c ).

[0085] Turn now Figure 6B At an appropriate dielectric layer thickness (e.g., 72 nm), a Cr absorber layer is used to absorb the dielectric material. Figure 6A The second harmonic is shown, and it provides a dazzling blue color. Furthermore, Figure 6C A method for providing red color by absorbing the first harmonic with a Cr absorber at different dielectric layer thicknesses (e.g., 125 nm) is described. However, Figure 6C It was also explained that the use of Cr absorber layers can lead to a greater angle dependence than expected for multilayer stacks, i.e., greater than the expected Δλ. c big.

[0086] It should be understood that, for the color red, compared to blue, the relatively large λ c The shift is due to the very narrow hue space of the dark red color and the fact that the Cr absorber layer absorbs wavelengths associated with non-zero electric fields, meaning it does not absorb light when the electric field is zero or close to zero. Thus, Figure 7A This describes how the zero or non-zero point differs for the wavelength of light at different incident angles. Such factors lead to... Figure 7B The angle-dependent absorption shown refers to the difference in absorption rate curves at 0° and 45°. Therefore, to further refine the multilayer stack design and angle-independent performance, absorber layers that absorb, for example, blue light are used, regardless of whether the electric field is zero or not.

[0087] In particular, Figure 8A This illustrates a multilayer stack with a Cu absorber layer replacing a Cr absorber layer, extending across a dielectric ZnS layer. The result of using such a "colored" or "selective" absorber layer is... Figure 8B The text shows that it proves that for in Figure 8A The multilayer stack shown exhibits a "closer" aggregation of absorption lines at 0° and 45°. Thus, Figure 8B and Figure 7B The comparison illustrates the significant improvement in the angle independence of the absorption rate when using a selective absorber layer instead of a non-selective absorber layer.

[0088] Based on the above, a proof-of-concept multilayer stacked structure was designed and fabricated. Furthermore, the computational / simulation results and actual experimental data of the proof-of-concept sample were compared. Specifically, and through… Figure 9 As shown in the graph, a bright red color was produced (wavelengths greater than 700 nm are typically not visible to the human eye), and very good agreement was achieved between the calculated / simulated data and the experimental optical data obtained from actual samples. In other words, the calculation / simulation can be used and / or used to simulate the results of multilayer stack designs and / or prior art multilayer stacks according to one or more embodiments disclosed herein.

[0089] Figure 10 This diagram shows the percentage reflectance versus the reflected EMR wavelength of another omnidirectional reflector design when exposed to white light at angles of 0° and 45° relative to the normal to the outer surface of the reflector. As the diagram shows, both the 0° and 45° curves illustrate very low reflectance (e.g., less than 10%) provided by the omnidirectional reflector for wavelengths less than 550 nm. However, as the diagram shows, the reflector provides a sharp increase in reflectance at wavelengths between 560 and 570 nm, reaching a maximum of approximately 90% at 700 nm. It should be understood that the portion or region of the graph on the right-hand side (IR side) of this diagram represents the IR portion of the reflection band provided by the reflector.

[0090] The dramatic increase in reflectivity provided by the omnidirectional reflector is characterized by the UV-side edge of each curve extending from a low-reflectivity portion with wavelengths less than 550 nm to a high-reflectivity portion (e.g., greater than 70%). The linear portion 200 of the UV-side edge is tilted at an angle (β) greater than 60° relative to the x-axis, having a length L of approximately 40 on the reflectivity axis and a slope of 1.4. In some cases, the linear portion is tilted at an angle greater than 70° relative to the x-axis, while in others, β is greater than 75°. Furthermore, the reflection band has a visible FWHM of less than 200 nm, and in some cases less than 150 nm, and in others less than 100 nm. Additionally, as will be stated in... Figure 10 The center wavelength λ of the visible reflection band described in the text c Defined as the wavelength equidistant between the UV-side edge of the reflection band at the visible FWHM and the IR edge of the IR spectrum.

[0091] It should be understood that the term "visible FWHM" refers to the width of the reflection band between the UV-side edge of the curve and the edge of the IR spectral range, beyond which the reflection provided by the omnidirectional reflector is invisible to the human eye. In this way, the inventive designs and multilayer stacks disclosed herein use the invisible IR portion of the electromagnetic radiation spectrum to provide dazzling or structural colors. In other words, despite the fact that a reflector can reflect a wider band of electromagnetic radiation extending into the IR region, the omnidirectional reflectors disclosed herein utilize the invisible IR portion of the electromagnetic radiation spectrum to provide a narrow band of reflected visible light.

[0092] Now for reference Figure 11 The figure shows graphs of the percentage reflectance versus wavelength of another seven-layer omnidirectional reflector when exposed to white light at angles of 0° and 45° relative to the reflector surface. Furthermore, the definition or characterization of the omnidirectional properties provided by the omnidirectional reflectors disclosed herein is shown. In particular, and when the reflection band provided by the reflector of the present invention has the maximum value, i.e., the peak value, as shown in the figure, each curve has a center wavelength (λ). c The wavelength of maximum reflectivity is defined as the wavelength at which it exhibits or experiences maximum reflectivity. The term "wavelength of maximum reflection" can also be used with λ. c .

[0093] like Figure 11 As shown, when from an angle of 45° (λ) c (45°) When observing the outer surface of an omnidirectional reflector, for example, when the outer surface is tilted at 45° relative to the eye observing the surface, compared to viewing it from 0° (λ) c (0°)), that is, when observing the surface perpendicularly to the surface, there exists λ compared to when the surface is viewed from a perspective of 0°. c The offset or displacement. λ c This offset (Δλ)c This provides a measure of the omnidirectional properties of an omnidirectional reflector. Naturally, zero offset, or completely no offset, would be a perfect omnidirectional reflector. However, the omnidirectional reflector disclosed herein can provide a Δλ of less than 50 nm. c To the human eye, the reflector's surface appears unchanged in color, and therefore, from a practical perspective, it is omnidirectional. In some cases, the omnidirectional reflector disclosed herein can provide a Δλ of less than 40 nm. c In other cases, it can provide a Δλ of less than 30 nm. c Furthermore, it can provide a Δλ of less than 20 nm in other cases. c And in other cases, it can provide a Δλ of less than 15 nm. c Δλ c Such offset can be determined by plotting the actual reflectivity of the reflector against the wavelength, and / or alternatively, if the material and layer thickness are known, it can be determined by modeling the reflector.

[0094] Another definition or characterization of the omnidirectional properties of a reflector can be determined by offsetting the side edges of a given set of angular reflection bands. For example, and referring to... Figure 11 The reflectivity (S) of the same reflector when viewed from 45° UV Compared to the UV-side edge at (45°), the reflectivity (S) of an omnidirectional reflector viewed from 0° is significantly higher. UV The offset or displacement of the UV side edge (ΔS) from (0°) UV This provides a measure of the omnidirectional properties of an omnidirectional reflector. It should be understood that the offset (ΔS) of the UV-side edge is measured at the visible FWHM. UV ), and / or the offset of the UV side edge (ΔS) can be measured at the visible FWHM. UV ).

[0095] Naturally, zero offset means no offset at all (ΔS) UV =0 nm) would characterize a perfect omnidirectional reflector. However, the omnidirectional reflector disclosed herein can provide a ΔS of less than 50 nm. UV To the human eye, the reflector's surface appears unchanged in color, and therefore, practically speaking, it is omnidirectional. In some cases, the omnidirectional reflector disclosed herein can provide a ΔS of less than 40 nm. UV In other cases, it can provide a ΔS of less than 30 nm. UV Furthermore, it can provide a ΔS of less than 20 nm in other cases. UV And in other cases, it can provide a ΔS of less than 15 nm. UV ΔSUV Such offset can be determined by plotting the actual reflectivity of the reflector against the wavelength, and / or alternatively, if the material and layer thickness are known, it can be determined by modeling the reflector.

[0096] The shift in omnidirectional reflection can also be measured using low-tone shift. For example, as in... Figure 12 As shown (see, for example, Δθ1), the hue shift of pigments prepared from a multilayer stack according to one aspect of the present invention is 30° or less, and in some cases, 25° or less, preferably less than 20°, more preferably less than 15°, and even more preferably less than 10°. In contrast, conventional pigments exhibit a hue shift of 45° or greater (see, for example, Δθ2). It should be understood that the hue shift associated with Δθ1 generally corresponds to red color; however, a low hue shift is relevant for any color reflected by the mixed omnidirectional structural color pigments disclosed herein.

[0097] exist Figure 13 Reference numeral 10 illustrates a schematic depiction of an omnidirectional multilayer stack according to another aspect disclosed herein. The multilayer stack 10 has a first layer 110 and a second layer 120. An optional reflector layer 100 may be included. Exemplary materials for the reflector layer 100 (sometimes referred to as the reflector core layer) may include, but are not limited to, Al, Ag, Pt, Cr, Cu, Zn, Au, Sn, combinations thereof, or alloys thereof. Thus, the reflector layer 100 may be a metallic reflector layer; however, this is not mandatory. Additionally, an exemplary thickness of the core reflector layer is between 30 and 200 nm.

[0098] A symmetrical pair of layers can be located on opposite sides of reflector layer 100, meaning reflector layer 100 can have another first layer arranged opposite to first layer 110, thus sandwiching reflector layer 100 between a pair of first layers. Furthermore, another second layer 120 can be arranged opposite to reflector layer 100, thus providing a five-layer structure. Therefore, it should be understood that the discussion of multilayer stacks provided herein also includes the possibility of mirrored structures with one or more central layers. Thus, Figure 13 This could be a description of half of a five-layer or multi-layer stacked structure.

[0099] In relation to the aspects discussed above, the first layer 110 can be an absorber layer, for example, a metal absorber layer having a thickness between 5 and 500 nm (inclusive). Furthermore, the second layer can be a dielectric absorber layer having a thickness between 5 and 500 nm (inclusive). The metal absorber layer 110 can be made of colored metallic materials such as Cu, bronze, or brass, or of materials such as amorphous Si, Ge, TiN, and combinations thereof. The dielectric absorber layer 120 can be made of Fe₂O₃.

[0100] like Figure 13 The aspects shown and having dimensions as shown in Table 1 below exhibit Figure 14 The reflectance spectrum is shown in the figure. As shown in the figure, Cu or its alloys or other colored reflectors with the thicknesses shown in Table 1, such as TiN layer 110 and Fe2O3 dielectric absorber layer 120, provide such a reflectance spectrum, wherein wavelengths less than approximately 550-575 nm have a reflectance of less than 10-15%, and wavelengths greater than approximately 575-600 nm correspond to hues between 0-40°, preferably between 10-30°, on the a*b*Lab color map. Furthermore, the chromaticity of the visible light reflection band is greater than 70, preferably greater than 80, and more preferably equal to or greater than 90.

[0101] Table 1

[0102] <![CDATA[ layer ]]> <![CDATA[ Material ]]> <![CDATA[ Thickness (nm) ]]> 100 Al 80.0 110 Cu or its alloys such as brass and bronze. 184.5 120 <![CDATA[Fe2O3]]> 28.6

[0103] Figure 14 The example shows viewing angles of 0° and 45°, as shown in the image. Figure 13 The reflection spectrum of such a multilayer stack is shown. As illustrated in the figure, the offset (ΔS) of the UV side edge at the FWHM is shown. UV =S UV (0°)–S UV (45°) less than 50 nm, preferably less than 30 nm, and still more preferably less than 20 nm, and even more preferably less than 10 nm. Considering the bandwidth in the visible spectrum, a shift in the frequency band of reflection between angles 0 and 45° corresponds to a color change that is not significant to the human eye.

[0104] Figure 15 It shows Figure 13 The absorption of the design shown corresponds to wavelength. As illustrated in the figure, the multilayer stack 10 absorbs more than 80% of the visible light spectrum up to approximately 575 nm. Furthermore, this aspect 10 absorbs more than 40% of all wavelengths up to approximately 660 nm. Thus, the combination of the metal absorbing layer 110 and the dielectric absorbing layer 120 provides a visible reflection band that has a hue between 0 and 40°, and preferably between 10 and 30°, in the a*b*Lab color space, i.e., the reflected wavelengths in the red color spectrum.

[0105] Figure 16A diagram of this aspect 10 is shown as a function of percentage reflectance, the wavelength of the reflected light, and the viewing angle. As the 3D contour plot shows, the reflectance is very low, i.e., less than 20% for wavelengths between 400-550-575 nm and at viewing angles between 0 and 45-50°. However, there is a sharp increase in percentage reflectance at wavelengths between approximately 550-600 nm.

[0106] Another method or technique for describing the omnidirectional properties of the multilayer stacked bodies disclosed in this invention is as follows: Figure 17 The graph shows the curves of chromaticity and hue versus viewing angle. Figure 17 It shows Figure 13 The reflective properties are shown, wherein the hue at angles between 0 and 45° is between 20 and 30, and has a change or shift of less than 10°, preferably less than 5°. Furthermore, for all viewing angles between 0 and 45°, the chromaticity is between 80 and 90, where chromaticity (C*) is defined as... a* and b* are the coordinates of the colors reflected by a multilayer stack when exposed to broadband electromagnetic radiation (such as white light) in the Lab color space or mapping.

[0107] Figure 18 Displayed or plotted Figure 13 The aspects shown are hues on the a*b*Lab color space map (see the data points indicated by the arrows). A region between 15 and 40° is also shown on this map. It should be understood that these two points are used to illustrate a 0° viewing angle relative to the normal to the outer surface of the multilayer stack. Additionally, it should be understood that viewing angles between 0 and 45°, such as... Figure 13 The hue in this aspect shown does not shift outside the 15-40° hue range. In other words, this aspect indicates a low hue shift, for example, less than 30°, preferably less than 20°, and still more preferably less than 10°. It should also be further understood that... Figure 13 The aspect shown can also be designed to provide single-band visible light with a hue between 0-40°, and curves can be plotted on... Figure 18 It is preferably a single-band visible light with a hue between 10-30°.

[0108] Turn now Figure 19The accompanying drawing, with reference numeral 20, generally illustrates a method for manufacturing an omnidirectional high-chromaticity red structural pigment. Method 20 includes a step 202 of dry deposition of a reflective core layer, followed by a step 210 of dry deposition of a metal absorber layer onto the dry-deposited reflective core layer. Then, in step 220, a dielectric absorber layer is dry-deposited or wet-deposited onto the metal absorber layer. It should be understood that steps 210 and 220 can be repeated to create additional layers on the dry-deposited reflective core layer. Furthermore, the dry-deposited reflective core layer can be deposited onto the metal absorber layer, or a wet-deposited dielectric layer can be deposited onto the metal absorber layer.

[0109] The embodiments and aspects described above are for illustrative purposes only, and variations, modifications, etc., will be apparent to those skilled in the art and still fall within the scope of this invention. Thus, the scope of this invention is defined by the claims and all their equivalents.

Claims

1. Omnidirectional high-chromaticity red structural pigment, comprising: Multilayer stacked bodies, which have: Reflective core layer; A metal absorber layer extending across the reflective core layer; and A dielectric absorber layer extending across the metal absorber layer; in, The multi-layered stacked body reflects a b A single-band visible light with a hue between 0-40° on the Lab color map, when viewed from all angles between 0-45° perpendicular to the outer surface of the multilayer stack, the single-band visible light in a b The Lab color map has a hue shift within the range of 0-40°. The overall thickness of the multilayer stack is less than 3 micrometers.

2. The omnidirectional high-chromaticity red structural pigment of claim 1, wherein, The reflective core layer has a thickness between 50 and 200 nanometers, including the end value.

3. The omnidirectional high-chromaticity red structural pigment of claim 2, wherein, The reflective core layer is made of reflective metals selected from the following: Al, Ag, Pt, Sn and combinations thereof.

4. The omnidirectional high-chromaticity red structural pigment of claim 2, wherein, The reflective core is made of a colored metal selected from the following: Au, Cu, brass, bronze, and combinations thereof.

5. The omnidirectional high-chromaticity red structural pigment of claim 2, wherein, The metal absorber layer has a thickness between 5 and 500 nanometers, including the end value.

6. The omnidirectional high-chromaticity red structural pigment of claim 5, wherein, The metal absorber layer is made of the following materials: Cu, bronze, brass, amorphous Si, Ge, TiN, and combinations thereof.

7. The omnidirectional high-chromaticity red structural pigment of claim 5, wherein, The dielectric absorber layer has a thickness between 5 and 500 nm, including the end values.

8. The omnidirectional high-chromaticity red structural pigment of claim 7, wherein, The dielectric absorber layer is made of Fe2O3.

9. The omnidirectional high-chromaticity red structural pigment of claim 5, wherein, The reflective core layer is a central reflective core layer, and the metal absorber layers are a pair of metal absorber layers extending across the opposite sides of the central reflective core layer, with the central reflective core layer sandwiched between the pair of metal absorber layers.

10. The omnidirectional high-chromaticity red structural pigment of claim 9, wherein, The dielectric absorber layer is a pair of dielectric absorber layers, with the central reflective core layer and the pair of metal absorber layers sandwiched between the pair of dielectric absorber layers.

11. A method for preparing an omnidirectional high-chromaticity red structural pigment, the method comprising: Multilayer stacks are manufactured using the following methods: Dry deposition of reflective core layer; Dry deposition traverses the metal absorber layer extending from the reflective core layer; Dry or wet deposition extends the dielectric absorber layer across the metal absorber layer; and Wherein, the multilayer stacked body reflects at a b A single-band visible light with a hue between 0-40° on the Lab color map, when viewed from all angles between 0-45° perpendicular to the outer surface of the multilayer stack, the single-band visible light in a b The Lab color map has a hue shift within the range of 0-40°. The overall thickness of the multilayer stack is less than 3 micrometers.

12. The method of claim 11, wherein, The multi-layered stack reflects in a b The Lab color map shows visible light with hues between 10-30°, and in this a b The Lab color map has a hue offset between 10 and 30 degrees.

13. The method of claim 11, wherein, The reflective core layer has a thickness between 50 and 200 nanometers, including the end value.

14. The method of claim 13, wherein, The reflective core layer is made of reflective metals selected from the following: Al, Ag, Pt, Sn and combinations thereof.

15. The method of claim 13, wherein, The reflective core is made of colored metals selected from the following: Au, Cu, brass, bronze, and combinations thereof.

16. The method of claim 13, wherein, The metal absorber layer has a thickness between 5 and 500 nanometers, including the end values.

17. The method of claim 16, wherein, The metal absorber layer is made of the following materials: Cu, bronze, brass, amorphous Si, Ge, TiN and combinations thereof.

18. The method of claim 16, wherein, The dielectric absorber layer has a thickness between 5 and 500 nanometers, including the end value, and is made of Fe2O3.

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