JP2020060800A - Omnidirectional high-chroma red structural color with combination metal absorber and dielectric absorber layers - Google Patents

Abstract

To provide a high-chroma red omnidirectional structural color pigment with a minimum number of layers.SOLUTION: A high-chroma omnidirectional red structural color pigment is in a form of a multilayer stack that has 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 a single band of visible light with a hue between 0° and 40°, preferably between 10° and 30°, on an abLab color map. The single band of visible light has a hue shift of less than 30° on the abLab color map when viewed from all angles between 0° and 45° normal to an outer surface of the multilayer stack.SELECTED DRAWING: Figure 8A

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part application (CIP) of US patent application Ser. No. 14 / 607,933 filed Jan. 28, 2015, which is further incorporated by CIP of U.S. patent application Ser. No. 14 / 471,834, which is further CIP of U.S. patent application Ser. No. 14 / 460,511, filed Aug. 15, 2014, which is also Apr. 2014. CIP of U.S. patent application Ser. No. 14/242429 filed on 1st December, which is further CIP of U.S. patent application Ser. No. 14/138499 filed Dec. 23, 2013, which is further 2013 CIP of US patent application Ser. No. 13/913402 filed June 8, 2013, which is further incorporated by reference in US patent application Ser. No. 13/7606 filed February 6, 2013. 99 CIP, which is also the CIP of US patent application Ser. No. 13/572071, filed August 10, 2012, all of which are incorporated by reference in their entireties.

  The present invention relates to a multilayer laminate structure that exhibits a highly saturated red color when exposed to broadband electromagnetic radiation and observed from various angles with minimal or imperceptible color shift.

  Pigments made from multilayer structures are known. In addition, pigments that exhibit or provide highly saturated omnidirectional structural colors are also known. However, such prior art pigments required as many as 39 thin film layers to obtain the desired color characteristics.

  It is understood that the costs associated with producing thin film multilayer pigments are proportional to the number of layers required. Thus, the costs associated with producing highly saturated omnidirectional structural colors using multilayer stacks of dielectric materials can be prohibitive. Therefore, a high saturation omnidirectional structural color with a minimal number of thin film layers required is desirable.

  In addition to the above, it is also understood that the design of red pigments faces additional difficulties in addition to those of pigments of other colors such as blue, green, etc. In particular, controlling the angular independence for the red case requires thicker dielectric layers and, as a result, higher order harmonic designs, ie second order and possibly third order. This is difficult because the presence of harmonics is unavoidable. Also, the dark red hue space is very narrow. Thus, the red multi-layer stack has a higher angular variance.

  In view of the above, a high chroma red omnidirectional structural color pigment with a minimum number of layers is desirable.

An omnidirectional high chroma red structural color pigment is provided. This omnidirectional structural color pigment is a multilayer laminate having a reflective core layer, a metal absorber layer extending over the reflective core layer, and a dielectric absorber layer extending over the metal absorber layer. It is a form. The multilayer stack reflects a single band of visible light having a hue between 0 and 40 ° on the a ^* b ^* Lab color map, preferably between 10 and 30 °. In addition, this single band of visible light is less than 30 ° on the a ^* b ^* Lab color map when viewed from all angles between 0 and 45 ° perpendicular to the outer surface of the multilayer stack. Of the hue shift so that the resulting color shift is not perceptible to the human eye.

  The reflective core layer has a thickness between 50 and 200 nanometers (nm) inclusive of the lower and upper limits, and is made of a reflective metal such as aluminum (Al), silver (Ag), platinum (Pt), tin. (Sn), combinations of these, and the like, and the like. The reflective core layer may also be made of a colorful metal, such as gold (Au), copper (Cu), brass, bronze, and the like.

The metal absorber layer may have a thickness between 5 and 500 nm inclusive of the lower and upper limits and may be colored metals such as copper (Cu), gold (Au), bronze (Cu-Zn alloy), brass. It may be made from a material such as (Cu-Sn alloy), amorphous silicon (Si), or a colored nitride material such as titanium nitride (TiN). The dielectric absorber layer may have a thickness, including upper and lower limits, between 5 and 500 nm and is made of a colored dielectric material, such as, but not limited to, iron oxide (Fe ₂ O ₃ ). You may

  The reflective core layer, metal absorber layer, and / or dielectric absorber layer may be a dry deposited layer. However, the dielectric absorber layer may be a wet deposited layer. In addition, the reflective core layer may be a central reflective core layer and the metal absorber layer may be a pair of metallic absorber layers extending over opposite sides of the central reflective core layer, ie, The central reflective core layer is sandwiched between a pair of metal absorber layers. Further, the dielectric absorber layer may be a pair of dielectric absorber layers, whereby the central reflective core layer and the pair of metal absorber layers are between the pair of dielectric absorber layers. Sandwiched between.

  A process for making such an omnidirectional high saturation red structural color includes dry depositing a reflective core layer, dry depositing a metal absorber layer that extends over the reflective core layer, and over the metal absorber layer. Producing the multilayer stack by dry or wet deposition of the extending dielectric absorber layer. By this method, a hybrid manufacturing process can be used to create omnidirectional high chroma red structural colors that can be used for pigments, coatings, and the like.

FIG. 1 is a schematic diagram of an omnidirectional structural color multilayer stack made from a dielectric layer, a selective absorption layer (SAL), and a reflector layer. FIG. 2A is a schematic diagram of a zero or near-zero electric field point in a ZnS dielectric layer exposed to electromagnetic radiation (EMR) having a wavelength of 500 nm. FIG. 2B shows the square of the absolute value of the electric field versus the thickness of the ZnS dielectric layer shown in FIG. 2A (| E | ² when exposed to EMR having wavelengths of 300, 400, 500, 600, and 700 nm. ) Is shown in the graph. FIG. 3 is a schematic diagram of a dielectric layer that extends over a substrate or reflector layer and is exposed to electromagnetic radiation at an angle θ with respect to a direction normal to the outer surface of the dielectric layer. FIG. 4 is a schematic diagram of a ZnS dielectric layer with a Cr absorber layer located at zero or near zero electric field point in the ZnS dielectric layer in the case of an incident EMR having a wavelength of 434 nm. FIG. 5 shows the reflectance with respect to the reflected EMR wavelength in a multilayer laminate having no Cr absorber layer exposed to white light (Example: FIG. 2A) and a multilayer laminate having a Cr absorber layer (Example: FIG. 4). This is a graph showing the percentage. FIG. 6A is a graph showing the first and second harmonics of a ZnS dielectric layer (eg, FIG. 2A) extending over an Al reflector layer. FIG. 6B shows a ZnS dielectric layer extending over the Al reflector layer as well as a Cr absorber layer disposed within the ZnS dielectric layer to absorb the second harmonic shown in FIG. 6A. 3 is a graph showing the reflectance percentage with respect to the reflected EMR wavelength in the multilayer laminate having the above. FIG. 6C has a ZnS dielectric layer extending over the Al reflector layer plus a Cr absorber layer disposed within the ZnS dielectric layer such that the first harmonic shown in FIG. 6A is absorbed. 6 is a graphical representation of reflectance percentage for reflected EMR wavelength in a multilayer stack. FIG. 7A is a graphical depiction of the electric field squared versus the dielectric layer thickness showing the angular dependence of the electric field of the Cr absorber layer upon exposure to incident light of 0 and 45 degrees. FIG. 7B shows the percent absorptance of the Cr absorber layer for reflected EMR wavelength when exposed to white light at angles of 0 and 45 ° (0 ° is normal to the plane) with respect to the vertical direction of the outer surface. Is shown in the graph. FIG. 8A is a schematic diagram of a red omnidirectional structural color multilayer laminate in an embodiment disclosed herein. 8B graphically illustrates the percent absorptance of the Cu absorber layer shown in FIG. 8A versus reflected EMR wavelength when the multilayer stack shown in FIG. 8A is exposed to white light at angles of incidence of 0 and 45 °. It is a thing. FIG. 9 is a graph showing a comparison of calculated / simulated and experimental data for percent reflectance versus reflected EMR wavelength in a proof-of-concept red omnidirectional structural color multilayer stack exposed to white light at an incident angle of 0 °. Is. FIG. 10 is a graphical representation of percent reflectance with respect to wavelength for an omnidirectional structural color multilayer stack in the embodiments disclosed herein. FIG. 11 is a graphical representation of percent reflectance with respect to wavelength for an omnidirectional structural color multilayer stack in accordance with the embodiments disclosed herein. FIG. 12 is a graphical representation of a portion of an a ^* b ^* color map using the CIELAB (Lab) color space, where a paint made from conventional paints and pigments in embodiments disclosed herein. The chroma and hue shifts of (Sample (b)) are compared. FIG. 13 is a schematic diagram of a red omnidirectional structural color multilayer laminate according to another embodiment disclosed herein. FIG. 14 is a graph showing the reflectance percentage with respect to the wavelength in the embodiment shown in FIG. FIG. 15 is a graph showing the absorptance percentage with respect to the wavelength in the embodiment shown in FIG. FIG. 16 is a graphical representation of reflectance percent vs. wavelength vs. viewing angle for the embodiment shown in FIG. FIG. 17 is a graph showing the saturation and the hue with respect to the observation angle in the mode shown in FIG. FIG. 18 is a graphical representation of the colors reflected by the embodiment shown in FIG. 13 for an a ^* b ^* Lab color map. FIG. 19 is a schematic diagram of a process for making an omnidirectional red structural color multilayer laminate in an aspect disclosed herein.

  An omnidirectional high chroma red structural color pigment is provided. This omnidirectional high chroma red structural color pigment is in the form of a multilayer stack having a reflective core layer, a metal absorber layer, and a dielectric absorber layer. The metal absorber layer extends over the reflective core layer and, in some examples, is located directly on or over the reflective core layer. The dielectric absorber layer extends over the metal absorber layer, and in some examples is located directly in contact with or on the metal absorber layer. The multilayer stack may be a symmetric stack, that is, the reflective core layer is a central reflective core layer adjacent to a pair of metal absorber layers, the pair of metal absorber layers being one. Adjacent to the pair of dielectric absorber layers.

The multilayer stack reflects a single band of visible light having a red color hue between 0 and 40 °, preferably between 10 and 30 ° on the a ^* b ^* Lab color map. In addition, this single-band hue shift of visible light is a ^* b ^* Lab color when viewed from all angles between 0 and 45 ° perpendicular to the outer surface of the multilayer stack. It is less than 30 ° on the map, preferably less than 20 °, more preferably less than 10 °. Thus, the single band hue shift of reflected visible light may be in the 0-40 ° region and / or in the 10-30 ° region on the a ^* b ^* Lab color map.

  The reflective core layer may be a dry deposited layer with a thickness between 50 and 200 nm inclusive of the lower and upper limits. The term "dry deposition" means dry deposition methods such as physical vapor deposition (PVD) methods including electron beam evaporation, sputtering, chemical vapor deposition (CVD), plasma CVD, and the like. In some examples, the reflective core layer is made of a reflective metal such as Al, Ag, Pt, Sn, combinations thereof, and the like. In other examples, the reflective core layer is made from colored metals such as Au, Cu, brass, bronze, combinations thereof, and the like. It is understood that the terms "brass" and "bronze" refer to copper-zinc and copper-tin alloys known to those skilled in the art, respectively.

  The metal absorber layer may also be a dry deposited layer deposited on the reflective core layer. As another option, the reflective core layer may be deposited on the metal absorber layer. The metal absorber layer may have a thickness between 5 and 500 nm inclusive of the lower and upper limits, and is a colored metal such as Cu, bronze or brass, or amorphous silicon (Si), germanium (Ge). , TiN, and the like. For the purposes of this disclosure, the term "metal absorber layer" is understood to include materials not normally known as metals, such as amorphous Si, Ge, TiN and the like.

The dielectric absorber layer may be a dry or wet deposited layer further deposited on the metal absorber layer. As another option, the metal absorber layer may be deposited on the dielectric absorber layer. The dielectric absorber layer may have a thickness between 5 and 500 nm inclusive, including upper and lower limits, and may be made of a dielectric material such as iron oxide (Fe ₂ O ₃ ) and the like. . The term "wet deposition" also means wet deposition methods such as sol-gel methods, spin coating methods, wet chemistry deposition techniques, and the like.

  The total thickness of the multilayer stack may be less than 3 microns, preferably less than 2 microns, more preferably less than 1.5 microns, and even more preferably less than 1.0 micron. In addition, the multi-layer laminate may have a total of 9 or less layers, preferably a total of 7 or less layers, more preferably a total of 5 or less layers.

Referring to FIG. 1, a design having a first dielectric material layer DL ₁ over which a lower reflector layer (RL) extends and a selective absorption layer SAL extending over the DL ₁ layer is shown. , Shown. In addition, another DL ₁ layer may be provided and extended over the selective absorption layer, or it may not be provided. The figure further shows that all incident electromagnetic radiation is either reflected by the multilayer structure or selectively absorbed.

  The design as shown in FIG. 1 corresponds to the different techniques used for the desired multilayer stack design and manufacture. In particular, a zero or near-zero energy point thickness in the dielectric layer is used and will be discussed below.

  For example, FIG. 2A is a schematic diagram of a ZnS dielectric layer extending across an Al reflector core layer. The ZnS dielectric layer has a total thickness of 143 nm, and for incident electromagnetic radiation with a wavelength of 500 nm the zero or near zero energy point is at 77 nm. In other words, the ZnS dielectric layer exhibits zero or near zero electric field at a distance of 77 nm from the Al reflector layer for incident electromagnetic radiation (EMR) having a wavelength of 500 nm. In addition, Figure 2B provides a graphical representation of the energy field across the ZnS dielectric layer at several different incident EMR wavelengths. As shown in the graph, the dielectric layer has a zero electric field at a thickness of 77 nm for a wavelength of 500 nm, but for an EMR wavelength of 300, 400, 600, and 700 nm, a zero electric field at a thickness of 77 nm is zero. Absent.

Regarding the calculation of the electric field point of zero or near zero, FIG. 3 shows that the total thickness “D”, the incremental thickness “d”, and the refractive index “n” on the substrate or core layer 2 having the refractive index n _s. Shows a dielectric layer 4 having Incident light strikes the outer surface 5 of the dielectric layer 4 at an angle θ with respect to a line 6 that is perpendicular to the outer surface 5 and is reflected from the outer surface 5 at the same angle θ. Incident light is transmitted through the outer surface 5 into the dielectric layer 4 at an angle θ _F with respect to the line 6 and strikes the surface 3 of the substrate layer 2 at an angle θ _s .

In a single dielectric layer, θ _s = θ _F and the energy / electric field (E) can be expressed as E (z), where z = d. From Maxwell's equation, the electric field is for s-polarized light:

  Can be expressed as, for p-polarized light:

Where k = 2π / λ, where λ is the wavelength desired to be reflected. Also, α = n _s sin θ _s , where “s” corresponds to the substrate of FIG.

  Is the dielectric constant of the layer as a function of z. Therefore, for s-polarized light,

  And for p-polarized light,

  Is.

  It is 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 it is shown as Can:

  Of course, "i" is the square root of -1. boundary condition

And the following relational expression:
For s-polarized light, q _s = n _s cos θ _s (6)
For p-polarized light, q _s = n _s / cos θ _s (7)
For s-polarized light, q = ncos θ _F (8)
For p-polarized light, q = n / cos θ _F (9)
φ = k ・ n ・ dcos (θ _F ) (10)
By using u (z) and v (z),

  Can be expressed as Therefore, for s-polarized light:

Where φ = k · n · dcos (θ _F ), and for p-polarized light:

And here:
α = n _s sin θ _s = n sin θ _F (15)
q _s = n _s / cos θ _s (16) and q _s = n / cos θ _F (17)
Is.

Therefore, in the simple case of θ _F = 0, or normal incident light, φ = k · n · d and α = 0.

  This allows the equation to be solved for the thickness “d”, ie for the position or location in the dielectric layer where the electric field is zero.

  Referring now to FIG. 4, Equation 19 was used to calculate the zero or near-zero electric field point in the ZnS dielectric layer shown in FIG. 2A when exposed to EMR having a wavelength of 434 nm. The electric field point at or near zero was calculated to be 70 nm (unlike 77 nm for a wavelength of 500 nm). In addition, a 15 nm thick Cr absorber layer was inserted at a thickness or distance of 70 nm from the Al reflector core layer to obtain a ZnS-Cr interface with zero or near-zero electric field. In such a structure of the present invention, light having a wavelength of 434 nm is transmitted through the Cr-ZnS interface, but light having no wavelength of 434 nm is absorbed. In other words, the Cr-ZnS interface has an electric field of zero or close to zero for light with a wavelength of 434 nm, so light of 434 nm is transmitted through this interface. However, the Cr-ZnS interface does not have a zero or near-zero electric field for light that does not have a wavelength of 434 nm, and thus such light is present in the Cr absorber layer and / or Cr-ZnS. It is absorbed by the interface and not reflected by the Al reflector layer.

  It is understood that some percentage of the desired light within ± 10 nm of 434 nm is transmitted through the Cr-ZnS interface. However, it is also understood that such narrow band reflected light, eg, 434 ± 10 nm, still provides a vivid structural color to the human eye.

  The results for the Cr absorber layer in the multi-layer stack of FIG. 4 are shown in FIG. 5 where the percent reflectance for reflected EMR wavelength is shown. There is a narrow reflection peak at about 400 nm, but a much broader peak at about 550 + nm, as shown by the dashed line corresponding to the ZnS dielectric layer shown in FIG. 4 without the Cr absorber layer. To do. In addition, there is still a significant amount of reflected light in the 500 nm wavelength range. Therefore, there are double peaks that prevent the multilayer laminate from having or exhibiting a structural color.

  In contrast, the solid line in FIG. 5 corresponds to the structure shown in FIG. 4 with the Cr absorber layer. As shown, there is a sharp peak at approximately 434 nm and a sharp decrease in reflectance for wavelengths above 434 nm is obtained with the Cr absorber layer. It is understood that the sharp peaks represented by the solid lines appear visually as vivid / structural colors. Also shown in FIG. 5 is the position where the reflection peak or band width is measured, ie, the band width is specified by the 50% reflectance of the maximum reflection wavelength, which is the full width at half maximum (FWHM). Also known as

  Regarding the omnidirectional behavior of the multilayer stack shown in FIG. 4, the thickness of the ZnS dielectric layer can be designed or set so that only the first harmonic of the reflected light is obtained. While this is sufficient for the "blue" color, it is understood that additional consideration is needed for the generation of the "red" color. For example, a thicker dielectric layer is required and, as a result, higher order harmonic designs, i.e., the presence of second and possibly third order harmonics, is unavoidable, thus resulting in angular independence for red. Is difficult to control. Also, the dark red hue space is very narrow. Therefore, the red multilayer laminate has a higher angular variation.

To overcome the high angular variation for red, this application discloses a unique and novel design / structure that results in a red that is angle independent. For example, FIG. 6A shows that the outer surface of the dielectric layer exhibits first and second harmonics for incident white light when observed from 0 and 45 ° to the normal of the outer surface. Is shown. As shown in the graphical illustration, the thickness of the dielectric layer provides a low angular dependence (small Δλ _c ), but such multilayer stacks have blue (first harmonic) and red (second harmonic) Wave) and is therefore not suitable for the desired "red only" color. Therefore, the concept / structure of using an absorber layer to absorb unwanted harmonic sequences has been developed. FIG. 6A also shows the position of the central wavelength (λ _c ) of the reflection band with respect to a certain reflection peak and the dispersion or shift (Δλ _c ) of the central wavelength when the sample is observed from 0 and 45 °. Examples are also given.

Referring now to FIG. 6B, the second harmonic shown in FIG. 6A is absorbed by the Cr absorber layer at the appropriate dielectric layer thickness (eg, 72 nm), resulting in a clear blue color. Further, FIG. 6C shows that a red color is obtained by absorbing the first harmonic by Cr absorbers having different dielectric layer thicknesses (for example, 125 nm). However, FIG. 6C also shows that the use of a Cr absorber layer can result in greater angular dependence than desired by the multilayer stack, ie, greater than desired Δλ _c .

The relatively large shift of λ _c for red compared to blue is that the dark red hue space is very narrow and that the Cr absorber layer absorbs wavelengths associated with a non-zero electric field: It is understood that it is due to not absorbing light when the electric field is zero or close to zero. Thus, FIG. 7A shows that at different angles of incidence, the zero or non-zero field point for the light wavelength is different. Such a factor results in the angle-dependent absorption shown in FIG. 7B, ie the difference between the 0 ° and 45 ° absorption curves. Therefore, in order to further improve the design and the angle-independent performance of the multilayer stack, an absorber layer is used which absorbs, for example, blue light, whether the electric field is zero or not.

  In particular, FIG. 8A shows a multilayer stack in which a Cu absorber layer instead of a Cr absorber layer extends across the dielectric ZnS layer. The results with such "colored" or "selective" absorber layers are shown in Figure 8B, which shows that the 0 ° and 45 ° absorption curves in the multilayer stack shown in Figure 8A are very "more". It shows that they are "close" together. Therefore, a comparison between FIG. 8B and FIG. 7B shows that the angle independence of absorption is greatly improved when the selective absorber layer is used instead of the non-selective absorber layer.

  Based on the above, a proof-of-concept multilayer laminate was designed and manufactured. In addition, the calculation / simulation results and actual experimental data for the proof-of-concept sample were compared. In particular, as shown in the plot of the graph in FIG. 9, a bright red color is generated (wavelengths above 700 nm are usually not visible to the human eye), and the experimental light obtained from the calculation / simulation and the actual sample. The data were in very good agreement. In other words, the calculations / simulations can and / or simulate the results of multilayer stack designs and / or prior art multilayer stacks in one or more embodiments disclosed herein. Used for.

  FIG. 10 is a plot of percent reflectivity versus reflected EMR wavelength for another omnidirectional reflector design when exposed to white light from angles of 0 and 45 ° with respect to the vertical direction of the outer surface of the reflector. Show. As shown from this plot, at wavelengths below 550 nm, both 0 ° and 45 ° curves show that this omnidirectional reflector gives very low reflectance, eg less than 10%. Is shown. However, as shown by these curves, the reflector shows a sharp increase in reflectance at wavelengths between 560 and 570 nm, reaching a maximum of approximately 90% at 700 nm. It is understood that the portion or region of the graph to the right of the curve (IR side) represents the IR portion of the reflection band provided by the reflector.

The sharp increase in reflectance provided by the omnidirectional reflector is due to the UV-sided edge of each curve extending from the low reflectance portion to the high reflectance portion at wavelengths below 550 nm, eg> 70. Characterized by%. The straight portion 200 at the UV end has a length L and a slope of 1.4 which is tilted at an angle (β) of more than 60 ° to the x-axis and is approximately 40 on the reflectance axis. This straight line portion may be inclined at an angle of more than 70 ° with respect to the x-axis, and β may be more than 75 °. The reflection band also has a visible FWHM of less than 200 nm, in some examples a visible FWHM of less than 150 nm, and in other examples a visible FWHM of less than 100 nm. In addition, the central wavelength λ _c of the visible reflection band shown in FIG. 10 is defined as the wavelength equidistant from the UV side end of the reflection band in the visible FWHM and the IR end of the IR spectrum.

  The term "visible FWHM" refers to the reflection band between the UV-side end of this curve and the end of the IR spectral range beyond which the reflection provided by the omnidirectional reflector is not visible to the human eye. Is understood to mean the width of. By this method, the inventive designs and multilayer laminates disclosed herein use the invisible IR portion of the electromagnetic radiation spectrum to provide a vivid or structural color. In other words, the omnidirectional reflectors disclosed herein provide a narrow band of reflective visible light despite the fact that the reflector may reflect a much wider band of electromagnetic radiation extending into the IR region. It utilizes the invisible IR portion of the electromagnetic radiation spectrum to provide light.

Referring now to FIG. 11, a plot of percent reflectance versus wavelength for another seven-layer design omnidirectional reflector when exposed to white light from angles of 0 and 45 ° to the face of the reflector. Is shown. In addition, the definition or characterization of the omnidirectional features provided by the omnidirectional reflectors disclosed herein is also provided. In particular, if the reflection band provided by the reflector of the present invention has a maximum, or peak, as shown in the figure, each curve has a central wavelength (defined as the wavelength at which it exhibits or causes maximum reflectance). λ _c ). The term maximum reflection wavelength may be used for λ _c .

As shown in FIG. 11, when the outer surface of the omnidirectional reflector is viewed from an angle of 45 °, for example, when the outer surface is tilted at 45 ° with respect to the human eye viewing the surface (λ _c (45 ^o )), if the plane is viewed from an angle of 0 °, ie perpendicular to the plane ((λ _c (0 ^o )), shift or displacement of λ _c. This shift in λ _c (Δλ _c ) provides a measure of the omnidirectional properties of the omnidirectional reflector, which is, of course, a zero shift, that is, if no shift occurs, it is a fully omnidirectional reflector. However, the omnidirectional reflectors disclosed herein can provide a Δλ _c of less than 50 nm, which means to the human eye that the face of the reflector changes color. It looks as if it weren't, so from a practical point of view, this reflector is omnidirectional In some examples, the omnidirectional reflectors disclosed herein can provide a Δλ _c of less than 40 nm, in other examples a Δλ _c of less than 30 nm, and in yet other examples. , Δλ _c less than 20 nm, and in yet another example, Δλ _c less than 15 nm, such a shift in Δλ _c is due to a plot of actual reflectance versus wavelength at the reflector and / or As an option, if the materials and layer thicknesses are known, they can be specified by modeling the reflector.

Another definition or characterization of the omnidirectional characteristic of a reflector can be specified by a shift of the side edges relative to a set of angular reflection bands. For example, referring to FIG. 11, the UV side edge (S _UV (0 ^o )) for the reflection from the omnidirectional reflector observed from 0 °, the UV for the reflection by the same reflector observed from 45 °. The shift or displacement (ΔS _UV ) compared to the side edges (S _UV (45 ^o )) provides a measure of the omnidirectional properties of the omnidirectional reflector. It is understood that the UV edge shift (ΔS _UV ) may and / or may be measured in the visible FWHM.

Naturally, a zero shift, ie no shift at all (ΔS _UV = 0 nm), would be characterized as a perfectly omnidirectional reflector. However, the omnidirectional reflectors disclosed herein can provide a ΔS _UV of less than 50 nm, which will appear to the human eye as if the face of the reflector did not change color. , And thus from a practical point of view, this reflector is omnidirectional. In some examples, the omnidirectional reflectors disclosed herein can provide a ΔS _UV of less than 40 nm, in other examples a ΔS _UV of less than 30 nm, and in yet other examples, ΔS _UV less than 20 nm, and in yet another example, ΔS _UV less than 15 nm. Such a ΔS _UV shift is identified by plotting the actual reflectivity versus wavelength at the reflector and / or, alternatively, by modeling the reflector if the material and layer thickness are known. can do.

The shift in omnidirectional reflection can also be evaluated by the low hue shift. For example, the hue shift of the pigment produced from the multilayer laminate in the embodiments disclosed herein is 30 ° or less, as shown in FIG. 12 (see, for example, Δθ ₁ ), and in one example, the hue is The shift is less than or equal to 25 °, preferably less than 20 °, more preferably less than 15 °, even more preferably less than 10 °. In contrast, conventional pigments exhibit a hue shift of 45 ° or more (see, eg, Δθ ₂ ). The hue shift with Δθ ₁ generally corresponds to red, but the low hue shift is suitable for any color reflected by the hybrid omnidirectional structural color pigments disclosed herein. It is understood.

  A schematic view of an omnidirectional multilayer stack according to another aspect disclosed herein is shown at 10 in FIG. The multilayer laminate 10 has a first layer 110 and a second layer 120. A reflector layer 100 may be included if desired. Examples of materials for the reflector layer 100, which may also be referred to as a reflector core layer, include, but are not limited to, Al, Ag, Pt, Cr, Cu, Zn, Au, Sn, and combinations thereof. Or an alloy may be mentioned. Therefore, the reflector layer 100 may be a metallic reflector layer, but this is not a requirement. In addition, the typical thickness of the core reflector layer ranges between 30 and 200 nm.

  There may be a pair of symmetrical layers on either side of the reflector layer 100, that is, the reflector layer 100 may be a first layer such that the reflector layer 100 is sandwiched between a pair of first layers. It may have another first layer disposed opposite the one layer 110. In addition, another second layer 120 may be placed on the opposite side of the reflector layer 100 so that a five layer structure is provided. Therefore, it should be understood that the discussion of multilayer stacks provided herein also includes the possibility of mirror image structures for one or more central layers. Thus, FIG. 13 may be a half-view of a five-layer multi-layer stack.

In contrast to the embodiments discussed above, the first layer 110 may be an absorber layer, eg, a metal absorber layer having a thickness between 5 and 500 nm inclusive inclusive. . Further, the second layer may be a dielectric absorber layer having a thickness between 5 and 500 nm inclusive of the upper and lower limits. The metal absorber layer 110 may be made of a colored metallic material such as Cu, bronze, brass, or amorphous Si, Ge, TiN, and combinations thereof. The dielectric absorber layer 120 may be made of Fe ₂ O ₃ .

The embodiment shown in FIG. 13 and having the dimensions shown in Table 1 below exhibited the reflectance spectrum shown in FIG. As shown in this figure, Cu or its alloys, or other colored reflectors, such as TiN layer 110 and Fe2O3 dielectric absorber layer 120, having the thickness shown in Table 1, are less than 15-20%. A wavelength of generally less than 550-575 nm with a reflectance of 550 nm and a wavelength of generally 575-600 nm corresponding to a hue between 0-40 °, preferably between 10-30 ° on the a ^* b ^* Lab color space map. It provided a reflectance spectrum with wavelengths above. In addition, the saturation for the visible light reflection band is more than 70, preferably more than 80, more preferably 90 or more.

The reflection spectrum of a multilayer stack as shown in FIG. 13 is shown graphically in FIG. 14 for 0 ° and 45 ° 0 viewing angles. As shown in the figure, the shift of the UV side edge of the FWHM (ΔS _UV = S _UV (0 ^o ) −S _UV (45 ^o )) is less than 50 nm, preferably less than 30 nm, even more preferably less than 20 nm, Even more preferably it is less than 10. Together with the width of the band in the visible spectrum, the shift of the reflection band between the 0 and 45 ° angles corresponds to a color change that is not perceptible to the human eye.

FIG. 15 shows the absorption for wavelength in the design shown in FIG. As shown in this figure, the multilayer stack 10 absorbs over 80% of the visible light spectrum at wavelengths up to approximately 575 nm. In addition, embodiment 10 absorbs more than 40% of all wavelengths up to approximately 660 nm. Therefore, the combination of the metal absorption layer 110 and the dielectric absorption layer 120 has a visible reflection band having a hue in the a ^* b ^* Lab color space of 0 to 40 °, preferably 10 to 30 °, that is, , Provides a reflection wavelength in the red spectrum.

  A graphical representation of aspect 10 as a function of percent reflectance, reflected wavelength, and viewing angle is shown in FIG. As shown in this 3D contour plot, at wavelengths between 400-550 nm and 575 nm and viewing angles between 0 and 45-50 °, the reflectance is very low, ie less than 20%. However, at wavelengths between approximately 550 and 600 nm, a sharp increase in reflectance percent is seen.

Another method or technique for describing the omnidirectional properties of the inventive multilayer laminate disclosed herein is a plot of saturation and hue versus viewing angle, as shown in FIG. FIG. 17 shows the reflection properties of the embodiment shown in FIG. 13, where the hue for angles between 0 and 45 ° is between 20 and 30 and its change or shift is less than 10 °, It is preferably less than 5 °. In addition, the saturation is between 80 and 90 for all viewing angles between 0 and 45 °, where the saturation (C ^* ) is

, A ^* and b ^* are the coordinates in the Lab color space or map for the colors reflected by the multilayer stack when exposed to broadband electromagnetic radiation, such as white light.

FIG. 18 shows or plots the hue of the embodiment shown in FIG. 13 (see data points indicated by arrows) on the a ^* b ^* Lab color space map. Areas between 15-40 ° are also shown on the map. It is understood that these two points have been shown for a viewing angle of 0 ° with respect to the direction perpendicular to the outer surface of the multilayer stack. In addition, it is also understood that at the observation angle of 0 to 45 °, the hue in the case of the embodiment shown in FIG. 13 does not deviate from the hue region of 15 to 40 °. In other words, these embodiments exhibit low hue shifts, for example less than 30 °, preferably less than 20 ° and even more preferably less than 10 °. Still further, it is understood that the embodiment shown in FIG. 13 may be designed such that a single band of visible light having a hue between 0 and 40 is provided and can be plotted on FIG. A single band of visible light having a hue of between 10 and 30 °.

  Referring now to FIG. 19, a process for making an omnidirectional high saturation red structured color is indicated generally by the numeral 20. Process 20 includes dry depositing a reflective core layer at step 202, and subsequent dry deposition of a metal absorber layer on the dry deposited reflective core layer at step 210. Then, in step 220, a dielectric absorber layer is dry or wet deposited on the metal absorber layer. It is understood that steps 210 and 220 may be repeated to create additional layers on the dry-deposited reflective core layer. In addition, the dry deposited reflective core layer may be deposited on the metal absorber layer as well as the wet deposited dielectric layer.

The above examples and aspects are for purposes of illustration only, and alterations, modifications, and the like will be apparent to those of ordinary skill in the art, and still fall within the scope of the invention. Accordingly, the scope of the invention is defined by the claims and their equivalents.
The invention further includes the following embodiments:
<Aspect 1>
Reflective core layer;
A multi-layer laminate having a metal absorber layer extending over the reflective core layer; and a dielectric absorber layer extending over the metal absorber layer,
The multilayer stack reflects a single band of visible light having a hue between 0 and 40 on the a ^* b ^* Lab color map, the single band of visible light being the single band of the multilayer stack. Having a hue shift in the range of 0-40 ° on the a ^* b ^* Lab color map when viewed from all angles between 0-45 ° perpendicular to the outer surface;
Highly saturated red structural color in all directions.
<Aspect 2>
The omnidirectional high-saturation red color according to 1 above, wherein the hue is in the range of 10 to 30 ° and the hue shift is in the range of 10 to 30 ° on the a ^* b ^* Lab color map. Structural color.
<Aspect 3>
The omnidirectional high-saturation red structural color according to 1 above, wherein the reflective core layer has a thickness between 50 and 200 nanometers inclusive of the lower and upper limits.
<Aspect 4>
An omnidirectional high-saturation red structural color as described in 3 above, wherein the reflective core layer is made of a reflective metal selected from the group consisting of Al, Ag, Pt, Sn, and combinations thereof.
<Aspect 5>
An omnidirectional high-saturation red structural color according to claim 3, wherein the reflective core layer is made of a colored metal selected from the group consisting of Au, Cu, brass, bronze, and combinations thereof.
<Aspect 6>
An omnidirectional high-saturation red structural color as described in 3 above, wherein the metal absorber layer has a thickness between 5 and 500 nanometers including the lower and upper limits.
<Aspect 7>
An omnidirectional high-saturation red structural color as described in 6 above, wherein the metal absorber layer is made from the group consisting of Cu, bronze, brass, amorphous Si, Ge, TiN, and combinations thereof.
<Aspect 8>
The omnidirectional high-saturation red structural color according to aspect 6, wherein the dielectric absorber layer has a thickness of 5 to 550 nanometers including the upper and lower limits.
<Aspect 9>
An omnidirectional high-saturation red structural color as described in 8 above, wherein said dielectric absorber layer is made of Fe ₂ O ₃ .
<Aspect 10>
The reflective core layer is a central reflective core layer, the metal absorber layer is a pair of metallic absorber layers extending over both sides of the central reflective core layer, 7. The omnidirectional high saturation red structural color according to 6 above, wherein a core layer is sandwiched between the pair of metal absorber layers.
<Aspect 11>
The dielectric absorber layer is a pair of dielectric absorber layers, and the central reflective core layer and the pair of metal absorber layers are sandwiched between the pair of dielectric absorber layers. The omnidirectional high-saturation red structural color described in 10 above.
<Aspect 12>
Dry depositing a reflective core layer;
Dry depositing a metal absorber layer extending over the reflective core layer;
Producing a multi-layer stack by dry or wet deposition of a dielectric absorber layer extending over the metal absorber layer, and the multi-layer stack comprising 0 on the a ^* b ^* Lab color map. On the a ^* b ^* Lab color map when reflecting visible light having a hue between ˜40 ° and viewed from all angles between 0 ° and 45 ° perpendicular to the outer surface of the multilayer stack. Having a hue shift in the range of 0-40 ° at
Method for manufacturing omnidirectional high saturation red structural color.
<Aspect 13>
Wherein the multilayer laminate, on the a ^* b ^* Lab color map has a hue between 10 to 30 °, and on the a ^* b ^* Lab color map, in the range of the 10 to 30 ° 13. The method according to 12 above, which reflects visible light having a hue shift.
<Aspect 14>
13. The method according to 12, wherein the reflective core layer has a thickness between 50 and 200 nanometers, including upper and lower limits.
<Aspect 15>
15. The method of 14, wherein the reflective core layer is made of a reflective metal selected from the group consisting of Al, Ag, Pt, Sn, and combinations thereof.
<Aspect 16>
15. The method of claim 14, wherein the reflective core layer is made of a colored metal selected from the group consisting of Au, Cu, brass, bronze, and combinations thereof.
<Aspect 17>
15. The method according to 14, wherein the metal absorber layer has a thickness of between 5 and 500 nanometers, including lower and upper limits.
<Aspect 18>
18. The method of claim 17, wherein the metal absorber layer is made from the group consisting of Cu, bronze, brass, amorphous Si, Ge, TiN, and combinations thereof.
<Aspect 19>
It said dielectric absorber layer has a thickness of 5 to 500 nm, including the upper and lower limits, and made of Fe ₂ O _3, the method according to the 17.

Claims (14)

Reflective core layer;
A metal absorber layer extending over the reflective core layer and in direct contact with the reflective core layer; and extending over the metal absorber layer and on the metal absorber layer A direct contact dielectric absorber layer made of Fe ₂ O ₃ ;
Comprising a multilayer laminate having
The multilayer stack reflects a single band of visible light having a hue between 0 and 40 on the a ^* b ^* Lab color map, the single band of visible light being the single band of the multilayer stack. Having a hue shift in the range of 0-40 ° on the a ^* b ^* Lab color map when viewed from all angles between 0-45 ° perpendicular to the outer surface;
A highly saturated red structural color pigment in all directions. The omnidirectional high saturation according to claim 1, wherein the hue is in the range of 10 to 30 ° and the hue shift is in the range of 10 to 30 ° on the a ^* b ^* Lab color map. Red structural color pigment.   An omnidirectional high chroma red structural color pigment according to claim 1 or 2, wherein the reflective core layer has a thickness between 50 and 200 nanometers.   The omnidirectional high saturation red structural color pigment according to any one of claims 1 to 3, wherein the reflective core layer is made of at least one of a reflective metal and a colored metal.   The omnidirectional high-saturation red structural color pigment according to claim 4, wherein the reflective metal is at least one of Al, Ag, Pt, Sn, Cr, and combinations thereof.   The omnidirectional high-saturation red structural color pigment according to claim 4, wherein the colored metal is at least one of Au, Cu, brass, bronze, and a combination thereof.   The omnidirectional high chroma red structural color pigment according to any one of claims 1 to 6, wherein the metal absorber layer has a thickness of between 5 and 500 nanometers.   Omni-directional high saturation according to any one of claims 1 to 7, wherein the metal absorber layer is made from at least one of Cu, bronze, brass, amorphous Si, Ge, TiN, and combinations thereof. Red structural color pigment.   An omnidirectional high chroma red structural color pigment according to any one of claims 1 to 8, wherein the dielectric absorber layer has a thickness between 5 and 500 nanometers.   The reflective core layer is a central reflective core layer, the metal absorber layer is a pair of metallic absorber layers extending over both sides of the central reflective core layer, The omnidirectional high chroma red structural color pigment according to any one of claims 1 to 9, wherein a core layer is sandwiched between the pair of metal absorber layers.   The dielectric absorber layer is a pair of dielectric absorber layers, and the central reflective core layer and the pair of metal absorber layers are sandwiched between the pair of dielectric absorber layers. The omnidirectional high-saturation red structural color pigment according to claim 10.   The omnidirectional high chroma red structural color pigment according to any one of claims 1 to 11, wherein the reflective core layer is a dry deposition layer.   The omnidirectional high chroma red structural color pigment according to claim 10, wherein the pair of metal absorber layers are dry deposition layers.   The omnidirectional high chroma red structural color pigment of claim 11, wherein the pair of dielectric absorber layers are dry or wet deposited layers.