JP6817407B2 - Omnidirectional high saturation red structural color with semiconductor absorber layer - Google Patents

Description

Mutual reference to related applications This application is a partial continuation application (CIP) of US Patent Application No. 14/607933, filed January 28, 2015, which is further filed on August 28, 2014. The CIP of US Patent Application No. 14/471834, which is further the CIP of US Patent Application No. 14/460511 filed August 15, 2014, which is further April 2014. The CIP of US Patent Application No. 14/2442429 filed on 1st, which is further the CIP of US Patent Application 14/138499, filed December 23, 2013, which is further 2013. The CIP of US Patent Application 13/913402, filed June 8, 2013, which is further the CIP of US Patent Application 13/760699, filed February 6, 2013. , CIP of US Patent Application No. 13/572071 filed August 10, 2012, all of which are incorporated by reference in their entirety.

The present invention relates to a multi-layered laminate structure that exhibits a highly saturated red color with minimal or perceptible color shifts when exposed to wideband electromagnetic radiation and observed from various angles.

Pigments made from multi-layer 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 properties.

It is understood that the cost associated with the production of thin film multilayer pigments is proportional to the number of layers required. Therefore, the cost associated with the production of highly saturated omnidirectional structural colors using a multilayer laminate of dielectric materials can be very high. Therefore, a highly saturated omnidirectional structural color that minimizes the 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 the case of pigments of other colors such as blue, green. In particular, the control of angular independence in the case of red requires a thicker dielectric layer, resulting in a higher harmonic design, i.e. second-order and possibly third-order. It is difficult because the presence of harmonics is unavoidable. Also, the dark red hue space is very narrow. Therefore, the red multilayer laminate has a higher angular variance.

Considering the above, a high-saturation red omnidirectional structural color pigment having a minimum number of layers is desirable.

An omnidirectional high saturation red structural color pigment is provided. This omnidirectional structural color pigment is a multilayer laminate having a reflective core layer, a semiconductor absorber layer extending over the reflective core layer, and a high refractive index dielectric layer extending over the semiconductor absorber layer. Is in the form of. The multilayer stack reflects a single band of visible light having a hue between 0 and 40 °, preferably between 10 and 30 ° on the a ^* b ^* Lab color map. In addition, this single band of visible light is less than 30 ° on the a ^* b ^* Lab colormap when viewed from all angles between 0 and 45 ° perpendicular to the outer surface of the multilayer laminate. Has a hue shift of, and thus the resulting color shift is not perceived by the human eye.

The reflective core layer has a thickness between 50 and 200 nanometers (nm), including the lower and upper limits, and is a reflective metal such as aluminum (Al), silver (Ag), platinum (Pt), tin. It may be made from (Sn), a combination thereof, and the same kind. The reflective core layer may also be made of colored metal, such as gold (Au), copper (Cu), brass, bronze, and the like.

The semiconductor absorber layer may have a thickness between 5 and 500 nm, including the lower and upper limits, and may be made of materials such as amorphous silicon (Si), germanium (Ge), and combinations thereof. The thickness of the high-refractive index dielectric layer is larger than 0.1 quarter wave thickness (QW) with respect to the target wavelength and is 4QW or less, and the target wavelength is a ^*. b ^* Have a default hue in the range 0-40 ° on the Lab colormap. The high refractive index dielectric layer is made of a dielectric material such as zinc sulfide (ZnS), titanium dioxide (TIO ₂ ), hafnium oxide (HfO ₂ ), niobium oxide (Nb ₂ O ₅ ), tantalum pentoxide (Ta ₂ O ₅ ). , And combinations thereof and the like.

The reflective core layer and the semiconductor absorber layer may be a dry deposition layer, while the high refractive index dielectric layer may be a wet deposition layer. In addition, the reflective core layer may be a central reflective core layer, and the semiconductor absorber layer may be a pair of semiconductor absorber layers extending across both sides of the central reflective core layer, i.e. The central reflective core layer is sandwiched between a pair of semiconductor absorber layers. Further, the high refractive index dielectric layer may be a pair of high refractive index layers, whereby the central reflective core layer and the pair of semiconductor absorber layers are of a pair of high refractive index dielectric layers. It is sandwiched between them.

The process for producing such an omnidirectional high-saturation red structural color is to dry-deposit the reflective core layer and dry-deposit the semiconductor absorber layer extending over the reflective core layer to produce a multi-layer laminate. Including doing. Next, a high refractive index dielectric layer extending over the semiconductor absorber layer is wet-deposited on it. By this method, a hybrid manufacturing process is used to produce an omnidirectional high saturation red structural color that can be used for pigments, coatings, and the like.

FIG. 1 is a schematic view of an omnidirectional structural color multilayer laminate made of a dielectric layer, a selective absorption layer (SAL), and a reflector layer. FIG. 2A is a schematic view of zero or near zero electric field points 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 (| E | ² ) with respect to the thickness of the ZnS dielectric layer shown in FIG. 2A when exposed to EMR having wavelengths of 300, 400, 500, 600, and 700 nm. ) Is shown in a graph. FIG. 3 is a schematic view of a dielectric layer that spreads over a substrate or reflector layer and is exposed to electromagnetic radiation at an angle θ in the direction perpendicular to the outer surface of the dielectric layer. FIG. 4 is a schematic view of a ZnS dielectric layer having a Cr absorber layer located at zero or near zero electric field points 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). The percentage is shown in a graph. FIG. 6A is a graph showing the first and second harmonics exhibited by the ZnS dielectric layer (eg, FIG. 2A) extending over the Al reflector layer. In FIG. 6B, in addition to the ZnS dielectric layer extending over the Al reflector layer, a Cr absorber layer arranged in the ZnS dielectric layer so as to absorb the second harmonic shown in FIG. 6A is shown. The reflectance percentage with respect to the reflected EMR wavelength in the multilayer laminate having is shown in a graph. FIG. 6C has a Cr absorber layer arranged in the ZnS dielectric layer so as to absorb the primary harmonics shown in FIG. 6A, in addition to the ZnS dielectric layer extending over the Al reflector layer. The reflectance percentage with respect to the reflected EMR wavelength in the multilayer laminate is shown in a graph. FIG. 7A is a graph showing the square of the electric field with respect to the thickness of the dielectric layer, which shows the angle dependence of the electric field of the Cr absorber layer at exposure to incident light of 0 and 45 degrees. FIG. 7B shows the percentage of absorption by the Cr absorber layer with respect to the reflected EMR wavelength when exposed to white light at angles of 0 and 45 ° with respect to the direction perpendicular to the outer surface (0 ° is perpendicular to the surface). Is shown in a graph. FIG. 8A is a schematic view of a red omnidirectional structural color multilayer laminate in the aspects disclosed herein. FIG. 8B is a graph showing the percentage of absorption rate of the Cu absorber layer shown in FIG. 8A with respect to the reflected EMR wavelength when the multilayer laminate shown in FIG. 8A is exposed to white light at incident angles of 0 and 45 °. It is a thing. FIG. 9 is a graph showing a comparison of experimental data with proof-of-concept red omnidirectional structural color multilayer laminates exposed to proof-of-concept red light with an incident angle of 0 ° for percent reflectance to reflected EMR wavelength. Is. FIG. 10 is a graph showing the reflectance percentage with respect to the wavelength in the case of the omnidirectional structural color multilayer laminate in the embodiment disclosed in the present specification. FIG. 11 is a graph showing the reflectance percentage with respect to the wavelength in the case of the omnidirectional structural color multilayer laminate in the embodiment disclosed in the present specification. FIG. 12 is a graph showing a part of an a ^* b ^* color map using the CIELAB (Lab) color space, which is a conventional paint and a paint made from a pigment in the embodiment disclosed in the present specification. The saturation and hue shifts of (sample (b)) are compared. FIG. 13A is a schematic view of a red omnidirectional structural color multilayer laminate in another aspect disclosed herein. FIG. 13B is a schematic view of a red omnidirectional structural color multilayer laminate in another aspect disclosed herein. FIG. 14A is a graph showing the percent reflectance with respect to the wavelength in the embodiment shown in FIG. 13A. FIG. 14B is a graph showing the percent reflectance with respect to the wavelength in the embodiment shown in FIG. 13B. FIG. 15 is a graph showing the absorptance percentage to wavelength in the embodiment shown in FIG. 13A. FIG. 16 is a graph showing the reflectance percent vs. wavelength vs. observation angle in the embodiment shown in FIG. 13A. FIG. 17 is a graph showing the saturation and hue with respect to the observation angle in the embodiment shown in FIG. 13A. FIG. 18 is a graph showing the colors reflected by the embodiments shown in FIGS. 13A and 13B with respect to the a ^* b ^* Lab colormap. FIG. 19 is a schematic diagram of a process for producing an omnidirectional red structural color multilayer laminate in an aspect disclosed herein.

An omnidirectional high saturation red structural color pigment is provided. This omnidirectional high-saturation red structural color pigment is in the form of a multilayer laminate having a reflective core layer, a semiconductor absorber layer, and a high refractive index dielectric layer. The semiconductor absorber layer extends over the reflective core layer and, in some examples, is directly in contact with or above the reflective core layer. The high refractive index dielectric layer extends over the semiconductor absorber layer and, in some examples, is in direct contact with or above the semiconductor absorber layer. The multilayer laminate may be a symmetrical laminate, that is, the reflective core layer is a central reflective core layer adjacent to a pair of semiconductor absorber layers, and the pair of semiconductor absorber layers is one. Adjacent to a pair of high refractive index dielectric layers.

The multi-layer laminate reflects a single band of visible light with a hue of red between 0-40 °, preferably 10-30 ° on the a ^* b ^* Lab colormap. In addition, this single band hue shift of visible light is a ^* b ^* Lab color when the multilayer laminate is viewed from all angles between 0 and 45 ° perpendicular to the outer surface of the multilayer laminate. It is less than 30 °, preferably less than 20 °, more preferably less than 10 ° on the map. Therefore, the single band hue shift of reflected visible light can be within the region of 15-45 ° on the a ^* b ^* Lab color map.

The reflective core layer may be a dry deposition layer with a thickness between 50 and 200 nm, including the lower and upper limits. The term "dry deposition" means physical vapor deposition (PVD) methods, including electron beam deposition, sputtering, chemical vapor deposition (CVD), plasma CVD, and similar dry deposition methods. In some examples, the reflective core layer is made from reflective metals such as Al, Ag, Pt, Sn, Cr, combinations thereof, and the like. In another example, 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" mean copper-zinc alloys and copper-tin alloys known to those skilled in the art, respectively.

The semiconductor absorber layer may also be a dry deposition layer deposited on the reflective core layer. As another option, the reflective core layer may be deposited on the semiconductor absorber layer. The semiconductor absorber layer may have a thickness between 5 and 500 nm including the lower and upper limits, and may be made of a semiconductor material such as amorphous silicon, germanium, a combination thereof, and the like. ..

The high refractive index dielectric layer may be a wet deposited layer, where the term "high refractive index" means a refractive index greater than 1.6. The term "wet deposition" also means wet deposition methods such as sol-gel method, spin coating method, wet chemistry deposition techniques, and the like. The high refractive index dielectric layer has a thickness D according to 0.1 QW <D ≦ 4QW, where QW is a quarter wavelength thickness relative to the wavelength of interest, i.e. QW = λ _t / 4. Where λ _t is the object or desired reflection wavelength. The wavelength of interest has a predetermined hue in the range 0-40 °, preferably 10-30 ° on the a ^* b ^* Lab color map. In some examples, the wavelength of interest is between 600 and 700 nanometers, and the dielectric layer is a dielectric material such as ZnS, TiO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , these. Made from combinations and similar ones.

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

Referring to FIG. 1, a design having a first dielectric material layer DL ₁ with an underlayer reflector layer (RL) extending over it and a selective absorption layer SAL extending over DL ₁ layer , Shown. In addition, another DL ₁ layer may or may not be provided and spread over the selective absorption layer. The figure also also shows that all incident electromagnetic radiation is either reflected by the multi-layer structure or selectively absorbed.

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

For example, FIG. 2A is a schematic view of a ZnS dielectric layer extending over the Al reflector core layer. The ZnS dielectric layer has a total thickness of 143 nm, and for incident electromagnetic radiation having a wavelength of 500 nm, an energy point of zero or near zero exists at 77 nm. In other words, the ZnS dielectric layer exhibits an electric field of zero or near zero at a distance of 77 nm from the Al reflector layer for incident electromagnetic radiation (EMR) having a wavelength of 500 nm. In addition, FIG. 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 with a thickness of 77 nm for wavelengths of 500 nm, whereas for EMR wavelengths of 300, 400, 600, and 700 nm, the electric field with a thickness of 77 nm is zero. Absent.

With respect to the calculation of zero or near zero electric field points, FIG. 3 shows a total thickness “D”, an incremental thickness “d”, and a refractive index “n” on a substrate or core layer 2 having a refractive index n _s. The dielectric layer 4 having the above is shown. The incident light hits the outer surface 5 of the dielectric layer 4 at an angle θ with respect 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 at an angle θ _F with respect to the line 6 into the dielectric layer 4, and hits the surface 3 of the base material layer 2 at an angle θ _s .

In a single dielectric layer, θ _s = θ _F , and the energy / electric field (E) can be represented as E (z), in which case z = d. From Maxwell's equation, the electric field is about s polarization:

Can be expressed as, about p-polarized light:

In the equation, k = 2π / λ, where λ is the wavelength desired to be reflected. Further, α = n _s sin θ _s , where “s” corresponds to the base material of FIG.

Is the permittivity of the layer as a function of z. Therefore, regarding s polarization,

And about p-polarized light

Is.

It is understood that the fluctuation of the electric field along the Z direction of the dielectric layer 4 can be estimated by the calculation of the unknown parameters u (z) and v (z), where it is shown as follows. Can:

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

And the following relational expression:
For s polarization, 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 = ncosθ _F (8)
For p-polarized light, q = n / cosθ _F (9)
φ = k · n · dcos (θ _F ) (10)
By using, u (z) and v (z) can be

Can be expressed as. Therefore, about s polarization:

And here, φ = k · n · dcos (θ _F ), and about p-polarized light:

And here:
α = n _s sinθ _s = nsinθ _F (15)
q _s = n _s / cosθ _s (16) and q _s = n / cosθ _F (17)
Is.

Therefore, in the simple situation where θ _F = 0, or vertically incident light, φ = k · n · d and α = 0:

This makes it possible to solve the equation with respect to the thickness "d", that is, with respect to the position or location in the dielectric layer where the electric field is zero.

Here, with reference to FIG. 4, equation 19 was used to calculate zero or near zero electric field points in the ZnS dielectric layer shown in FIG. 2A when exposed to EMR having a wavelength of 434 nm. The zero or near zero electric field point was calculated to be 70 nm (unlike 77 nm for a wavelength of 500 nm). Further, a Cr absorber layer having a thickness of 15 nm was inserted at a thickness or distance of 70 nm from the Al reflector core layer to obtain a ZnS—Cr interface having an electric field of zero or near zero. 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 a wavelength of 434 nm is absorbed. In other words, the Cr-ZnS interface has an electric field of zero or near zero with respect to light having a wavelength of 434 nm, so light at 434 nm passes through this interface. However, the Cr-ZnS interface does not have an electric field of zero or near zero for light that does not have a wavelength of 434 nm, so such light is 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 passes through the Cr-ZnS interface. However, it is also understood that such narrow band reflected light, such as 434 ± 10 nm, nevertheless provides a vivid structural color to the human eye.

The result of the Cr absorber layer in the multilayer laminate of FIG. 4 is shown in FIG. 5 in which the reflectance percentage with respect to the reflected EMR wavelength is shown. A narrow reflection peak is present at about 400 nm, but a much wider peak is present at about 550 + nm, as indicated by the dashed line corresponding to the ZnS dielectric layer shown in FIG. 4 without the Cr absorber layer. To do. In addition, a significant amount of reflected light is still present in the 500 nm wavelength region. 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 in the figure, there is a sharp peak at about 434 nm, and a sharp decrease in reflectance for wavelengths above 434 nm is obtained by the Cr absorber layer. It is understood that the sharp peaks represented by the solid lines appear visually as clear / structural colors. FIG. 5 also shows where the reflection peak or bandwidth is measured, i.e., the bandwidth is specified by 50% reflectance of the maximum reflection wavelength, which is the full width at half maximum (FWHM). Also known as.

With respect to the omnidirectional behavior of the multilayer laminate 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. It is understood that this is sufficient for the "blue" color, but further consideration is needed for the occurrence of the "red" color. Angle independence for red, for example, because a thicker dielectric layer is required, and as a result, higher harmonic design, i.e. the presence of second and in some cases third harmonics, is unavoidable. Is difficult to control. Also, the dark red hue space is very narrow. Therefore, the red multilayer laminate has higher angular variation.

To overcome the high angular variability for red, the present application discloses a unique and novel design / structure that results in angle-independent red. For example, FIG. 6A shows a dielectric layer showing primary and second harmonics with respect to incident white light when the outer surface of the dielectric layer is observed from 0 and 45 ° with respect to the normal of the outer surface. Is shown. As shown graphically, the thickness of the dielectric layer gives a low angular dependence (small Δλ _c ), but such multilayers are blue (first harmonic) and red (second harmonic). It has a combination of waves) 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 reflection peak and the dispersion or shift (Δλ _c ) of that central wavelength when the sample is observed from 0 and 45 °. An example is also shown.

Referring here to FIG. 6B, the second harmonics shown in FIG. 6A are absorbed by the Cr absorber layer at an appropriate dielectric layer thickness (eg 72 nm) to give a clear blue color. Further, FIG. 6C shows that a red color is obtained by absorbing the first harmonic with Cr absorbers having different dielectric layer thicknesses (eg, 125 nm). However, FIG. 6C also shows that the use of Cr absorber layers can result in greater angular dependence than desired by the multilayer laminate, i.e. greater than desired Δλ _c .

The relatively large shift of λ _c for red compared to blue means that the dark red hue space is very narrow and that the Cr absorber layer absorbs wavelengths associated with non-zero electric fields, ie. It is understood that this is due to the fact that the electric field does not absorb light when it is at or near zero. Therefore, FIG. 7A shows that different incident angles have different zero or non-zero electric field points with respect to the light wavelength. The result of such factors is the angle-dependent absorption shown in FIG. 7B, i.e., the difference between the 0 ° and 45 ° absorption curves. Therefore, in order to further improve the design and angle-independent performance of the multilayer laminate, for example, an absorber layer that absorbs blue light is used regardless of whether the electric field is zero or not.

In particular, FIG. 8A shows a multilayer laminate in which a Cu absorber layer extends over the dielectric ZnS layer instead of the Cr absorber layer. The results of using such a "colored" or "selective" absorber layer are shown in FIG. 8B, which shows that the 0 ° and 45 ° absorption curves in the multilayer laminate shown in FIG. 8A are very "more". It shows that it is "closely" organized. Therefore, a comparison between FIGS. 8B and 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 concept-proven multilayer laminate was designed and manufactured. In addition, the calculation / simulation results and actual experimental data for the concept proof sample were compared. In particular, as shown in the plot of the graph of FIG. 9, a clear red color is generated (wavelengths above 700 nm are usually invisible to the human eye), and experimental light obtained from calculation / simulation and actual samples. The data were in very good agreement. In other words, the calculations / simulations can and / or simulate the results of the multi-layer laminate design and / or prior art multi-layer laminate in one or more embodiments disclosed herein. Used for.

FIG. 10 is a plot of the percent reflectance for the reflected EMR wavelength in another omnidirectional reflector design when exposed to white light from angles 0 and 45 ° to the direction perpendicular to the outer surface of the reflector. Shown. As shown from this plot, at wavelengths below 550 nm, both the 0 ° and 45 ° curves have very low reflectance, eg less than 10%, obtained by this omnidirectional reflector. 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 on the right side (IR side) of the curve represents the IR portion of the reflection band provided by the reflector.

The sharp increase in reflectance provided by the omnidirectional reflector is the UV-sided edge of each curve extending from the low reflectance portion at wavelengths below 550 nm to the high reflectance portion, eg> 70. Characterized by%. The straight portion 200 at the UV side end is tilted at an angle (β) greater than 60 ° with respect to the x-axis and has a length L and a tilt of 1.4 which is approximately 40 on the reflectance axis. This straight line portion may be tilted at an angle of more than 70 ° with respect to the x-axis, and β may be more than 75 °. Also, the reflection band has a visible FWHM of less than 200 nm, in some examples a visible FWHM of less than 150 nm, and in others 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 a 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 beyond this the reflection provided by the omnidirectional reflector is invisible to the human eye at the end of the IR spectral range. It is understood to mean the width of. By this method, the designs and multilayers of the invention disclosed herein provide vivid or structural colors by using the invisible IR portion of the electromagnetic radiation spectrum. In other words, the omnidirectional reflectors disclosed herein are visible in a narrow band, despite the fact that the reflector can reflect a much wider band of electromagnetic radiation extending into the IR region. The invisible IR portion of the electromagnetic radiation spectrum is utilized to provide light.

Referring now to FIG. 11, a plot of percent reflectance with respect to wavelength in another 7-layer design omnidirectional reflector when exposed to white light from angles 0 and 45 ° with respect to the surface of the reflector. Is shown. In addition, definitions or characterization of omnidirectional properties provided by the omnidirectional reflectors disclosed herein are also provided. In particular, when the reflection band provided by the reflectors of the present invention has a maximum value, i.e. a peak, as shown in the figure, each curve has a central wavelength defined as the wavelength that indicates or causes maximum reflectance ( It has λ _c ). The term maximum reflected wavelength may be used for λ _c .

As shown in FIG. 11, when the outer surface of the omnidirectional reflector is observed from an angle of 45 °, for example, the outer surface is tilted 45 ° with respect to the human eye looking at the surface (λ _c). (45 ^o )), the shift or displacement of λ _c compared to when the surface is observed at an angle of 0 °, i.e., perpendicular to the surface ((λ _c (0 ^o ))). This shift of λ _c (Δλ _c ) provides a measure of the omnidirectional properties of the omnidirectional reflector. Of course, a zero shift, i.e., a completely omnidirectional reflector if no shift occurs. However, the omnidirectional reflector disclosed herein can provide a Δλ _c of less than 50 nm, which, to the human eye, causes the surface of the reflector to change color. It appears as if it were not, and therefore, from a practical point of view, this reflector is omnidirectional. In some examples, the omnidirectional reflectors disclosed herein are less than 40 nm Δλ _c. In another example, it is less than 30 nm Δλ _c , in yet another example it is less than 20 nm Δλ _c , and in yet another example it is less than 15 nm Δλ _c . Such a shift of Δλ _c is identified by a plot of the actual reflectance to wavelength in the reflector and / or, as another option, by modeling the reflector if the material and layer thickness are known. be able to.

Another definition or characterization of the omnidirectional property of the reflector can be identified by a shift of the side edge with respect to a set of angular reflection bands. For example, with reference to FIG. 11, the UV for reflections from the same reflector observed from 45 ° at the UV side edge ( _SUV (0 ^o )) for reflections from omnidirectional reflectors observed from 0 °. The shift or displacement (ΔS _UV ) compared to the side edge ( _SUV (45 ^o )) provides a measure of the omnidirectional properties of the omnidirectional reflector. It is understood that the shift at the UV side edge (ΔS _UV ) may be measured and / or done in the visible FWHM.

Of course, zero shift, that is, no shift at all (ΔS _UV = 0 nm), characterizes the reflector as a completely omnidirectional reflector. However, the omnidirectional reflectors disclosed herein can provide a ΔS _UV of less than 50 nm, as if the surface of the reflector did not change color to the human eye. Therefore, from a practical point of view, this reflector is omnidirectional. In some examples, the omnidirectional reflectors disclosed herein can provide ΔS _UVs below 40 nm, in other examples ΔS _UVs less than 30 nm, and in yet other examples. It is a ΔS _UV of less than 20 nm, and in yet another example, a ΔS _UV of less than 15 nm. Such ΔS _UV shifts are identified by a plot of the actual reflectance for wavelengths in the reflector and / or, as an alternative, by modeling the reflector if the material and layer thickness are known. can do.

The shift of 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, eg, Δθ ₁ ), and in some cases the hue. The shift is 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 more (see, eg, Δθ ₂ ). The hue shift associated 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. That is understood.

A schematic diagram of the omnidirectional multilayer laminate in another aspect disclosed herein is shown by reference numeral 10 in FIG. 13A. The multi-layer laminate 10 has a first layer 110 and a second layer 120. The reflector layer 100 may be included if desired. Examples of materials for the reflector layer 100, which may also be referred to as the reflector core layer, are, but are not limited to, Al, Ag, Pt, Cr, Cu, Zn, Au, Sn, and alloys thereof. Can be mentioned. Therefore, the reflector layer 100 may be a metal reflector layer, but this is not a requirement. In addition, the typical thickness of the core reflector layer is in the range between 30 and 200 nm.

A pair of symmetrical layers may be present on either side of the reflector layer 100, i.e., the reflector layer 100 is such that the reflector layer 100 is sandwiched between the pair of first layers. It may have another first layer located on the opposite side of the one layer 110. In addition, another second layer 120 may be placed on the opposite side of the reflector layer 100 to provide a five-layer structure. Therefore, it should be understood that the discussion of multi-layer laminates provided herein also includes the possibility of mirror image structures for one or more central layers. Therefore, FIG. 13A can be a half view of a five-layer multilayer laminate.

In contrast to the embodiments discussed above, the first layer 110 may be an absorber layer, eg, a semiconductor absorber layer having a thickness between 5 and 500 nm including the lower and upper limits. .. The semiconductor absorber layer 110 may be made of amorphous Si or Ge and, as shown in FIG. 14A, is generally electromagnetic so that wavelengths less than 550 to 575 nm have reflectance less than 15-20%. It may absorb radiation. The second layer 120 reflects a wavelength of more than 575-600 nm, which corresponds to a hue between 0-40 °, preferably between 10-30 ° on the a ^* b ^* Lab color space map. It may be a high refractive index dielectric layer having a thickness obtained by. In addition, the saturation for the visible light reflection band is greater than 70, preferably greater than 80, more preferably greater than 90 or greater. The reflection spectra of the multilayer laminate shown in FIG. 13A and having the layer thicknesses listed in Table 1 below are shown graphically in FIG. 14A for observation angles of 0 ° and 45 °. As shown in the figure, the shift of the center wavelength is less than 50 nm, preferably less than 30 nm, and even more preferably less than 20 nm. In addition, it is understood that the UV side of the reflection band is also a very small shift. Combined 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 perceived by the human eye.

Another aspect of the omnidirectional high-saturation red structural color in the form of a multi-layer laminate is shown by reference numeral 12 in FIG. 13B. Aspect 12 is similar to Aspect 10 shown in FIG. 13A, but extends over an additional absorber layer 112 extending over the high refractive index dielectric layer 120 and a second absorber layer 112. There is an additional high refractive index dielectric layer 122 present. The absorber layer 112 may be the same as or different from the absorber layer 110, that is, the layer 112 may be made of amorphous Si, Ge, or the like. Further, the second dielectric layer 122 may be the same as or different from the first dielectric layer 120. In FIG. 13B, the reflector layer 100 is sandwiched between the layers 110, 120, 112, 22 shown in the figure and another set of layers 110, 120, 112, 122 arranged opposite to them. It is understood that it can be a half-figure of a 9-layer laminate that is a central or core reflector layer.

The reflection spectrum of the multilayer laminate shown in FIG. 13B having the layer thickness shown in Table 2 below is shown in FIG. 14B. As shown in this figure, the wavelength shift at which a reflectance of 70% is shown is relatively small between observation angles of 0 and 45 ° perpendicular to the outer surface of the multilayer laminate. For example, the wavelength shift can be 50 nm, preferably 30 nm, more preferably 20 nm. Again, this shift in the visible spectrum occurs as a color shift that is not perceived by the human eye. As another option, omnidirectional characteristics are indicated or described by a low or small shift (ΔS _UV ) at the UV side of the reflection spectrum shown in the figure.

FIG. 15 shows absorption for wavelength in the design shown in FIG. 13A. As shown in this figure, the multilayer laminate 10 absorbs more than 80% of the visible light spectrum at wavelengths up to approximately 550 nm. In addition, aspect 10 absorbs more than 40% of all wavelengths up to 600 nm. Therefore, the combination of the absorption layer 110 and the dielectric layer 120 has a visible reflection band having a hue between 0 and 40 °, preferably between 10 and 30 ° in the a ^* b ^* Lab color space, that is, red. Provides the reflection wavelength of the spectrum.

FIG. 16 shows a graph showing the case of the tenth aspect as a function of the reflectance percentage, the reflected wavelength, and the observation angle. As shown in this 3D contour plot, the reflectance is very low, i.e. less than 20%, at wavelengths between 400 and 550 to 575 nm and at observation angles between 0 and 45 to 50 °. However, at a wavelength of approximately 600 nm, a sharp increase in percent reflectance is seen.

Another method or technique for describing the omnidirectional properties of the multilayer laminates of the invention disclosed herein is a plot of saturation and hue with respect to an observation angle, as shown in FIG. FIG. 17 shows the reflection characteristics of the embodiment shown in FIG. 13A, where the hue for an angle between 0 and 45 ° is between 20-30 and the change or shift is less than 10 °. is there. In addition, the saturation is between 80 and 90 for all observation angles between 0 and 45 °, where the saturation (C ^* ) is.

Defined as, a ^* and b ^* are the coordinates on the Lab color space or map with respect to the color reflected by the multilayer stack when exposed to wideband electromagnetic radiation such as white light.

FIG. 18 shows or plots the hues of the embodiments shown in FIGS. 13A (denoted as “A”) and 13B (denoted as “B”) on the a ^* b ^* Lab color space map. Regions between 15-40 ° are also shown on the map. It is understood that these two points are shown for the case of an observation angle of 0 ° with respect to the direction perpendicular to the outer surface of the multilayer laminate. In addition, it is also understood that at an observation angle of 0-45 °, the hue in the case of the embodiments shown in FIGS. 13A and 13B does not deviate from the hue region of 15-40 °. In other words, these embodiments exhibit a low hue shift, eg, a shift of less than 30 °, preferably less than 20 °, and even more preferably less than 10 °. Furthermore, the embodiments shown in FIGS. 13A and 13B may be designed to provide a single band of visible light with hues between 0 and 40 ° and to be plotted on FIG. Is also understood, preferably a single band of visible light having a hue between 10 and 30 °.

Here, with reference to FIG. 19, the process for producing an omnidirectional high saturation red structural color is schematically shown by reference numeral 20. Process 20 includes dry deposition of the reflective core layer in step 202, followed by dry deposition of the semiconductor absorber layer on the dry deposition reflective core layer in step 210. Then, in step 220, a high refractive index dielectric layer is wet-deposited on the dry-deposited semiconductor absorber layer. It is understood that steps 210 and 220 may be repeated to create additional layers on top of the dry sedimentary reflective core layer. In addition, the dry sedimentary reflective core layer may be deposited on the semiconductor absorber layer as well as the wet sedimentary dielectric layer.

A non-exhaustive list of materials from which dry deposition _nh dielectric layers may be formed is shown in Table 3 below.

The above examples and embodiments are for purposes of illustration only, and modifications, modifications, and the like are apparent to those skilled in the art and are further within the scope of the present invention. Therefore, the scope of the present invention is defined by the claims and all equivalents thereof.
The present invention further includes the following embodiments:
<Aspect 1>
Reflective core layer;
It has a multilayer laminate having a semiconductor absorber layer extending over the reflective core layer; and a high refractive index dielectric layer extending over the semiconductor absorber layer.
The multilayer laminate reflects a single band of visible light having a hue between 0 and 40 ° on the a ^* b ^* Lab color map, and the single band of visible light is that of the multilayer laminate. It has a hue shift within the range 0-40 ° on the a ^* b ^* Lab colormap when viewed from all angles between 0-45 ° perpendicular to the outer surface.
Omnidirectional high saturation red structural color.
<Aspect 2>
The omnidirectional high-saturation red according to aspect 1, wherein the hue is between 10 and 30 ° and the hue shift is within the range of 10 and 30 ° on the a ^* b ^* Lab color map. Structural color.
<Aspect 3>
The omnidirectional high saturation red structural color according to aspect 1, wherein the reflective core layer has a thickness between 50 and 200 nanometers including the lower and upper limits.
<Aspect 4>
The omnidirectional high-saturation red structural color according to aspect 3, wherein the reflective core layer is made of a reflective metal selected from the group consisting of Al, Ag, Pt, Sn, Cr, and combinations thereof.
<Aspect 5>
The omnidirectional high-saturation red structural color according to aspect 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>
The omnidirectional high saturation according to aspect 3, wherein the semiconductor absorber layer has a thickness between 5 and 500 nanometers including the lower and upper limits and is made of a group consisting of amorphous Si, Ge, and a combination thereof. Red structural color.
<Aspect 7>
The high refractive index dielectric layer has a thickness D according to the relational expression 0.1QW <D ≦ 4QW, QW is a quarter wavelength thickness with respect to the target wavelength, and the target wavelength is the a ^*. b ^{* The} omnidirectional high-saturation red structural color according to aspect 6, which has a predetermined hue within the range of 0 to 40 ° on the Lab color map.
<Aspect 8>
7. Aspect 7 in which the high refractive index dielectric layer is made of a dielectric material selected from the group consisting of ZnS, TiO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and combinations thereof. Omnidirectional high saturation red structural color.
<Aspect 9>
The reflective core layer is a central reflective core layer, and the semiconductor absorber layer is a pair of semiconductor absorber layers extending on both sides of the central reflective core layer, and the central reflective layer. The omnidirectional high-saturation red structural color according to aspect 8, wherein the core layer is sandwiched between the pair of semiconductor absorber layers.
<Aspect 10>
The high refractive index dielectric layer is a pair of high refractive index dielectric layers, and the central reflective core layer and the pair of semiconductor absorber layers are between the pair of high refractive index dielectric layers. The omnidirectional high-saturation red structural color according to aspect 9, which is sandwiched between.
<Aspect 11>
Dry deposition of reflective core layer;
Including dry deposition of a semiconductor absorber layer extending over the reflective core layer; and wet deposition of a high refractive index dielectric layer extending over the semiconductor absorber layer to produce a multilayer laminate. ,
The multilayer laminate reflects visible light having a hue between 15 and 40 ° on the a ^* b ^* Lab color map and is all between 0 and 45 ° perpendicular to the outer surface of the multilayer laminate. It has a hue shift within the range of 15-40 ° on the a ^* b ^* Lab color map when viewed from the angle of.
A method of producing a highly saturated red structural color in all directions.
<Aspect 12>
The method according to aspect 11, wherein on the a ^* b ^* Lab color map, the hue is between 10 and 30 ° and the hue shift is within the range of 10 and 30 °.
<Aspect 13>
The reflective core layer has a thickness between 50 and 200 nanometers, including the lower and upper limits, and is made from a reflective metal selected from the group consisting of Al, Ag, Pt, Sn, and combinations thereof. The method according to aspect 11.
<Aspect 14>
13. The method of aspect 13, 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 15>
13. The method of aspect 13, wherein the semiconductor absorber layer has a thickness between 5 and 500 nanometers, including the lower and upper limits.
<Aspect 16>
The method according to aspect 15, wherein the semiconductor absorber layer is made of a group consisting of amorphous Si, Ge, and a combination thereof.
<Aspect 17>
The high refractive index dielectric layer has a thickness D according to the relational expression 0.1QW <D ≦ 4QW, QW is a quarter wavelength thickness with respect to the target wavelength, and the target wavelength is the a ^*. b ^* The method of aspect 16, wherein the method has a predetermined hue within the range of 15-40 ° on the Lab color map.
<Aspect 18>
17. Aspect 17 in which the high refractive index dielectric layer is made of a dielectric material selected from the group consisting of ZnS, TiO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and combinations thereof. Method.
<Aspect 19>
Further comprising dry-depositing a pair of semiconductor absorber layers on both sides of the reflective core layer, the reflective core layer is sandwiched between the pair of dry-deposited semiconductor absorber layers. The method according to aspect 18.
<Aspect 20>
Further including wet deposition of a pair of high refractive index dielectric layers, the pair of dry deposited semiconductor absorber layers are sandwiched between the pair of wet deposited high refractive index dielectric layers. The method according to aspect 19.

Claims (11)

A method for producing a high-saturation red structural color pigment in all directions.
Dry deposition of reflective core layer;
Dry deposition of a semiconductor absorber layer extending over a reflective core layer; and wet deposition of a high refractive index dielectric layer extending over the semiconductor absorber layer;
Including the manufacture of multi-layer laminates by
The high refractive index dielectric layer has a thickness D according to the relational expression 0.1QW <D≤4QW, QW is a quarter wavelength thickness with respect to the target wavelength, and the target wavelength is a ^* b. ^* Has a default hue in the range 0-40 ° on the Lab colormap,
The multilayer laminate reflects a single band of visible light having the predetermined hue between 0 and 40 ° on the a ^* b ^* Lab color map, and the single band of visible light is the multilayer. A hue shift of 0 to 40 ° within the predetermined hue range on the a ^* b ^* Lab colormap when viewed from all angles between 0 and 45 ° perpendicular to the outer surface of the laminate. Have,
A method for producing an omnidirectional high-saturation red structural color pigment. The method of claim 1, wherein the hue is between 10 and 30 ° and the hue shift is within the range of 10 and 30 ° on the a ^* b ^* Lab color map. The method of claim 1 or 2, wherein the reflective core layer has a thickness between 50 and 200 nanometers. The method 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 method according to claim 4, wherein the reflective metal is at least one of Al, Ag, Pt, Sn, Cr, and a combination thereof. The method of claim 4, wherein the colored metal is at least one of Au, Cu, brass, bronze, and combinations thereof. The method according to any one of claims 1 to 6, wherein the semiconductor absorber layer has a thickness between 5 and 500 nanometers. The method according to any one of claims 1 to 7, wherein the semiconductor absorber layer is made of at least one of amorphous Si, Ge, and a combination thereof. Claims 1 to 8 wherein the high refractive index dielectric layer is made of a dielectric material selected from the group consisting of ZnS, TiO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and combinations thereof. The method according to any one of the above. A pair of semiconductor absorber layers are further dry-deposited on both sides of the reflective core layer, and the reflective core layer is sandwiched between the dry-deposited pair of semiconductor absorber layers. The method according to any one of claims 1 to 9. It further comprises wet-depositing a pair of high-refractive-index dielectric layers, with the dry-deposited pair of semiconductor absorber layers sandwiched between the pair of wet-deposited high-refractive-index dielectric layers. The method according to claim 10.