JP6816235B2 - High chroma omnidirectional structure color multilayer structure - Google Patents

Description

Cross-reference to related applications This application is a continuation-in-part (CIP) of US Patent Application Sequential No. 13 / 760,699 filed on February 6, 2013. U.S. Patent Application Sequential No. 13 / 760,699 is the CIP of U.S. Patent Application Sequential No. 13 / 021,730 filed on February 5, 2011. U.S. Patent Application Sequential No. 13 / 021,730 is a U.S. Patent Application Sequential No. 12 / 974,606 filed on December 21, 2010 (currently U.S. Patent No. 8,323,391). CIP. U.S. Patent Application Serial No. 12 / 974,606 is the CIP of U.S. Patent Application Sequential No. 12 / 388,395 filed on February 18, 2009. U.S. Patent Application Serial No. 12 / 388,395 is a U.S. Patent Application Sequential No. 11 / 837,529 (currently U.S. Patent No. 7,903,339) filed on August 12, 2007. CIP.

The present application is further the CIP of US Patent Application Sequential No. 12 / 893, 152, filed September 29, 2010. U.S. Patent Application Sequential No. 12 / 893,152 is the CIP of U.S. Patent Application Sequential No. 12 / 467,656 filed May 18, 2009.

The present application is further the CIP of US Patent Application Sequential No. 12 / 793, 772, filed June 4, 2010.

The present application is further the CIP of US Patent Application Sequential No. 13 / 57,071 filed on August 10, 2012. U.S. Patent Application Serial No. 13 / 527,071 is the CIP of U.S. Patent Application Sequential No. 13 / 021,730 filed on February 5, 2011. U.S. Patent Application Serial No. 13 / 021,730 is the CIP of U.S. Patent Application Sequential No. 12 / 793, 772 filed June 4, 2010. U.S. Patent Application Serial No. 12 / 793,772 is U.S. Patent Application Sequential No. 11 / 837,529 filed on August 12, 2007 (currently U.S. Patent No. 7,903,339). CIP.

The present application is further the CIP of US Patent Application Serial No. 13 / 014,398 filed on January 26, 2011. U.S. Patent Application Sequential No. 13/014,398 is the CIP of U.S. Patent Application Sequential No. 12 / 793, 772 filed June 4, 2010. U.S. Patent Application Sequential No. 12 / 793,772 is the CIP of U.S. Patent Application Sequential No. 12 / 686,861 filed on January 13, 2010. U.S. Patent Application Serial No. 12 / 686,861 is U.S. Patent Application Sequential No. 12 / 389,256 filed on February 19, 2009 (currently U.S. Patent No. 8,329,247). CIP.

Field of Invention The present invention relates to omnidirectional structural colors, especially to omnidirectional structural colors provided by metal and dielectric layers.

Background of the Invention Pigments formed from a multi-layer structure are known. In addition, pigments that exhibit or provide high chroma omnidirectional structural colors are also known.

However, such prior art pigments require as many as 39 thin film layers to obtain the desired color properties. It is understood that the costs associated with the production of thin film multilayer pigments are proportional to the number of layers required, and the costs associated with the production of high chroma omnidirectional structural colors using multilayer stacks of dielectric materials can be very high. Has been done. Therefore, a high chroma omnidirectional structural color that minimizes the number of thin film layers required is desirable.

Description of the Invention A high chroma omnidirectional structural color multilayer structure is provided. The structure includes a multi-layer stack. The multi-layer stack has a core layer, which may also be called a reflective layer, a dielectric layer extending over the core layer, and an absorbing layer extending over the dielectric layer. There is an interface between the dielectric layer and the absorption layer, and at the interface, there is an electric field of almost zero for the first incident electromagnetic wave length and a large electric field at the second incident electromagnetic wave length. Therefore, this interface allows high transmission of the first incident electromagnetic wave length through the interface and through the dielectric layer with reflectance from the core / reflective layer. However, this interface produces a high absorption of the second incident electromagnetic wave length. Therefore, the multi-layer stack produces or reflects light in a narrow band.

The core layer can have the complex index of refraction represented by the equation RI ₁ = n ₁ + ik ₁ , where n ₁ << k ₁ , where RI ₁ is the complex index of refraction and n ₁ is the refraction of the core layer. It is a rate, k ₁ is the extinction coefficient of the core layer, and i is √-1. In some cases, the core layer is formed from silver, aluminum, gold, or alloys thereof, preferably having a thickness between 50 nanometers (nm) and 200 nm.

The dielectric layer has a thickness of no more than twice the quarter wave (QW) of the central wavelength of the desired narrow band of reflected light. In addition, the dielectric layer can be formed from titanium oxide, magnesium fluoride, zinc sulfide, hafnium oxide, tantalum oxide, silicon oxide, or a combination thereof.

The absorbing layer has a complex refractive index whose refractive index is approximately equal to the extinction coefficient. Such materials include chromium, tantalum, tungsten, molybdenum, titanium, titanium nitride, niobium, cobalt, silicon, germanium, nickel, palladium, vanadium, iron oxide, and combinations or alloys thereof. Further, the thickness of the absorbing layer is preferably between 5 nm and 20 nm.

In some cases, the multilayer structure includes another dielectric layer that extends over the outer surface of the absorbing layer. Also, another absorption layer may be included between the core layer and the first dielectric layer. Such a structure provides a high chroma omnidirectional structural color with a minimum of two layers on the core layer.

It is a schematic diagram of a single dielectric layer on a substrate. It is a figure of the high chroma omnidirectional structure color multilayer structure according to the Example of this invention. It is a schematic diagram of the Example of this invention. It is a graph of the refractive index for the Example shown in FIG. 3 (a). It is a graph of the electric field passing through the thickness of the Example shown in FIG. 3A when the incident wavelength is 650 nm. It is a graph of the electric field over the example shown in FIG. 3A when the incident wavelength is 400 nm. It is a graph of the reflectance vs. the incident light wavelength when the dielectric layer thickness is 1.5QW for the embodiment shown in FIG. 3A when viewed at 0 ° and 45 °. It is a graph of the reflectance vs. the incident light wavelength when the dielectric layer thickness is 3QW for the embodiment shown in FIG. 3A when viewed at 0 ° and 45 °. It is a graph of the reflectance vs. the incident light wavelength when the dielectric layer thickness is 3.6QW for the example shown in FIG. 3A when viewed at 0 ° and 45 °. It is a graph of the reflectance vs. the incident light wavelength when the dielectric layer thickness is 6QW for the embodiment shown in FIG. 3A when viewed at 0 ° and 45 °. It is a graph of the comparison between the color characteristics on the a * b * color map about the target color area of the hue equal to 280. It is a graph of the Example shown in FIG. 3A, showing the absorption degree vs. the incident light wavelength for the dielectric layer (L1) and the absorption layer (L1) shown in FIG. 2A. It is a graph of the example shown in FIG. 3 (a) which shows the reflectance vs. the incident light wavelength for the example shown in FIG. 3 (a) when viewed at 0 ° and 45 °. It is a graph of the example shown in FIG. 3A showing the hue and the chroma vs. incident angle. It is a schematic diagram of another Example according to this invention. It is a graph of the refractive index for the structure shown in FIG. 7A. It is a graph of the electric field passing through the thickness of the Example shown in FIG. 7A when the incident light wavelength is 420 nm. It is a graph of the electric field over the thickness of the example shown in FIG. 7 (a) and passing through the thickness of the example shown in FIG. 7 (a) when the incident light wavelength is 560 nm. .. It is a graph of the reflectance vs. the incident light wavelength for the embodiment shown in FIG. 7A when viewed from 0 ° and 45 °. FIG. 7 is a graph of absorption vs. incident light wavelength for the layer shown in the embodiment of FIG. 7A. FIG. 7 is a graph of hue and chroma reflectance vs. incident angle for the embodiment shown in FIG. 7 (a). It is a schematic diagram of the example of 5 layers (5L) according to this invention. It is a schematic diagram of the example of 7 layers (7L) according to this invention. A single Al layer structure (Al core), an Al core + ZnS layer structure (Al core + ZnS), a five-layer structure shown in FIG. 9 (a), and a seven-layer structure shown in FIG. 9 (b). It is a graph of reflectance vs. incident light wavelength. The case of the five-layer structure shown in FIG. 8A having a dielectric layer thickness that produces the reflection of the first and second harmonics of the desired narrow band reflected light, and the case of the desired narrow band reflected light. Dielectric layer that produces only the first harmonic of the above, and the case of the five-layer structure shown in FIG. 9A and the dielectric that produces only the first harmonic of the reflected light in a desired narrow band. It is a graph of comparison between the color characteristics in the a * b * color map for the target color area of the hue equal to 80 in the case of the 7-layer structure shown in FIG. 9A having the body layer thickness. .. It is a graph of comparison between the multilayer structure of the present technology and the multilayer structure provided by the embodiment of the present invention on the a * b * color map. It is a schematic diagram of a 5-layer multilayer structure according to the embodiment of the present invention. It is a schematic diagram of the 7-layer multilayer structure according to the Example of this invention.

Detailed Description of the Invention A high chroma omnidirectional structural color multilayer structure is provided. Therefore, the multilayer structure is used as a paint pigment, a thin film that provides a desired color, and the like.

The high chroma omnidirectional structural color multilayer structure includes a core layer and a dielectric layer extending over the core layer. Further, the absorption layer extends over the dielectric layer with an interface in between. The thickness of the absorption layer and / or the dielectric layer shows that the interface between these two layers shows an electric field of almost zero at the first incident electromagnetic wave length and a large electric field at the second incident electromagnetic wave length. Designed and / or manufactured as such. The second incident electromagnetic wave length is not equal to the first incident electromagnetic wave length.

A nearly zero electric field at an interface produces a high percentage of the first incident electromagnetic wave length transmitted through it, while a large electric field produces a high percentage of the second incident electromagnetic wave length absorbed by the interface. Should be understood. Thereby, the multilayer structure reflects electromagnetic radiation in a narrow band such as a narrow reflection band of less than 400 nm, less than 300 nm or less than 200 nm. Moreover, the narrow reflection band is viewed from different angles, for example, between 0 ° and 45 °, between 0 ° and 60 ° and / or between 0 ° and 90 °. , Its central wavelength shift is very low.

The core layer is formed from a material whose complex index of refraction is much smaller than the extinction coefficient for the material. The complex index of refraction is expressed by the equation RI ₁ = n ₁ + ik ₁ , where n ₁ is the index of refraction of the core layer material, k ₁ is the extinction coefficient of the core layer material, and i is the square root of -1. Materials that meet this criterion include silver, aluminum, gold, and alloys thereof. Furthermore, the thickness of the core layer can be between 10 nm and 500 nm in some cases, between 25 nm and 300 nm in other cases, and between 50 nm and 200 nm in other cases. possible.

The dielectric layer has a thickness of no more than twice (2QW) the quarter wave of the central wavelength of the narrow reflection band. QW is defined by the following formula.

QW = λ / (4 ・ n)
Where λ is the desired wavelength to be reflected and n is the index of refraction of the dielectric layer. In addition, the dielectric layer comprises titanium oxide (eg, TiO ₂ ), magnesium fluoride (eg, MgF ₂ ), zinc sulfide (eg, ZnS), hafnium oxide (eg, HfO ₂ ), niobium oxide (eg, Nb ₂ O). ₅ ), tantalum oxide (eg, Ta ₂ O ₅ ), silicon oxide (eg, SiO ₂ ), and combinations thereof.

For the absorbent layer, a material having a refractive index generally equal to the extinction coefficient for the material is used. Materials that meet this criterion include chromium, tantalum, tungsten, molybdenum, titanium, titanium nitride, niobium, cobalt, silicon, germanium, nickel, palladium, vanadium, iron oxide, and / or alloys or combinations thereof. In some cases, the thickness of the absorbent layer is between 5 nm and 50 nm, in other cases the thickness is between 5 nm and 20 nm.

Field with the desired thickness over the thin film structure with respect to the dielectric layer, without being bound by theory, FIG. 1, on the substrate or core layer 2 having a refractive index n _s, and the total thickness "D", increased It is a schematic diagram of the dielectric layer 4 having a thickness "d" and a refractive index "n". The incident light hits the outer surface 5 of the dielectric layer 4 at a certain angle θ with respect to the line 6 perpendicular to the surface, and is reflected from the outer surface 5 at the same angle. The incident light passes through the outer surface 5 and is transmitted through the dielectric layer 4 into the dielectric layer 4 at an angle θ _F with respect to the line 6 and hits the surface 3 of the substrate layer 2 at an angle θ _s as shown in the figure.

In the case of a single dielectric layer, θ _s = θ _F , and the electric field (E) can be represented as E (z) when z = d. From Maxwell's equations, the electric field can be expressed as follows for s-polarized light.

The p-polarized light can be expressed as follows.

In the equation, k = 2π / λ, where λ is the desired wavelength to be reflected. Further, α = n _s sin θ _s , and “s” in the equation corresponds to the substrate in FIG. 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 unknown parameters u (z) and v (z). In that case,

Can be shown. Boundary condition u | _{z = 0} = 1, v | _{z = 0} = q _s ,
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 polarization, q = ncosθ _F (8)
For p-polarized light, q = n / cosθ _F (9)
φ = k · n · d cos (θ _F ) (10)
U (z) and v (z) can be expressed as follows by using the relation.

and

Therefore, for s polarization with φ = k · n · d cos (θ _F ),

And about p polarization

And during the ceremony

Is. Therefore, in the case of simple states such as θ _F = 0 or vertical incident, φ = k · n · d, and α = 0,

As a result, when the electric field is zero, the thickness "d" to be solved is obtained.
The multilayer structure of the present invention includes a five-layer structure having a central core layer having a pair of dielectric layers on opposite sides of the core layer and a pair of absorbing layers extending over the outer surface of the dielectric layer. obtain. It includes a seven-layer multilayer structure in which another pair of dielectric layers extends over the outer surfaces of the two absorbing layers. The first five-layer structure described above includes different seven-layer structures including a pair of absorption layers extending between the opposing surfaces of the core layer and the dielectric layer. Further, with respect to the above 7-layer structure, a 9-layer multilayer structure in which yet another pair of absorption layers extends between the opposing surface of the core layer and the dielectric layer is included.

Here, with reference to FIG. 2, an example of a high chroma omnidirectional structural color multilayer structure is schematically shown by reference numeral 10. The multilayer structure 10 has a core or a reflective layer 100, and the dielectric layer 110 extends over the outer surface 102 of the reflective layer 100. Further, the absorption layer 120 extends over the dielectric layer 110 with an interface 112 sandwiched between them. As shown in FIG. 2, incident light is sent to the multilayer structure 10 and hits the multilayer structure 10. The reflected light is reflected from the multilayer structure 10.

A particular embodiment is shown in FIG. 3 (a) with reference to FIG. In this embodiment, the core layer 100 is made of aluminum, the dielectric layer 110 is made of ZnS, and the absorption layer 120 is made of chromium. FIG. 3B provides a graph showing the refractive indexes of the aluminum core layer 100, the ZnS dielectric layer 110, and the chromium absorbing layer 120. Further, FIG. 3B also shows the thickness of the dielectric layer 110 (60 nm) and the absorption layer 120 (5 nm).

3 (c) and 3 (d) provide a graph of an electric field (| E | ² (unit:%)) as a function of the thickness of the multilayer structure shown in FIG. 3 (a). As shown in FIGS. 3 (c) and 3 (d), when the wavelength is 650 nm, a relatively large electric field exists at the interface between the ZnS dielectric layer and the chromium absorbing layer. In contrast, when the incident wavelength is 400 nm, the electric field is almost zero at the interface between the ZnS dielectric layer and the chromium absorbing layer. For the purposes of this disclosure, the phrase "nearly zero" is defined as less than 25% | E | ² in some cases and 10% | E | ² in other cases. In yet other cases it is defined as less than 5%.

From the graphs shown in FIGS. 3 (c) and 3 (d), it is understood that the wavelength in the 400 nm region passes through the interface 112, while the wavelength in the 650 nm region is absorbed at the interface 112. .. Therefore, electromagnetic radiation in the 400 nm range passes through the interface 112, through the ZnS dielectric layer 110, is reflected from the core layer 100, and the reflected electromagnetic radiation then passes through the dielectric layer 110, the interface 112, and the absorption layer 120. By transmitting, a narrow band of reflected electromagnetic radiation is created by the multilayer structure 10. This provides a narrow band of reflected light and thus produces a structural color.

With respect to the omnidirectional action of the multilayer structure 10, the thickness of the dielectric layer 110 is designed or set so that only the first harmonic of the reflected light is provided. In particular, with reference to FIG. 4, FIG. 4 (a) shows the reflection characteristics of the multilayer structure 10 when viewed from 0 ° and 45 °. The dielectric layer 110 has a thickness of 1.5 QW with a desired wavelength of 400 nm, which is equal to 67 nm. The refractive index n of the ZnS dielectric material is given as follows.

n ≒ 2.2
As shown in FIG. 4 (a) and different from FIGS. 4 (b) to 4 (d), only the first harmonic of the reflected narrow band of electromagnetic radiation is provided. Specifically, if the dielectric layer thickness is greater than 2QW, there will be a second harmonic, a third harmonic, and a fourth harmonic. Therefore, the thickness of the dielectric layer 110 is important to provide omnidirectional structural color.

Here, with reference to FIG. 5, a comparison of color characteristics for a multilayer structure can be considered using an a * b * color map that uses the CIELAB color space. It is understood that the CIELAB color space is an opposite color space with dimensions L * for lightness and a * and b * for opposite color dimensions, based on the XYZ color space coordinates of the non-linearly compressed CIE space. The a * axis is perpendicular to the b * axis and forms a chromaticity plane. The L * axis is perpendicular to the chromaticity plane. The L * axis combined with the a * and b * axes perfectly represents the color attributes of interest such as purity, hue and brightness. Using non-professional language, very colorful stimuli (colors) appear bright and intense to the human eye, while less colorful stimuli appear dull, closer to gray. If there is no "colorfulness", the color is "neutral" gray, and an image without colorfulness is typically referred to as a grayscale image or grayscale image. In addition, color can be indicated by three attributes: colorfulness (also known as chroma or saturation), lightness (also known as brightness), and hue.

The color map shown in FIG. 5 has a targeted color area of hue equal to (b * / a *) inverse tangent = 280. The lines shown in this figure correspond to the change in color when viewed from between 0 ° and 80 °. In addition, these lines correspond to the first and second harmonics associated with the dielectric layer thicknesses of 1.67QW and 3QW, respectively. As shown in the figure, the lines corresponding to the first harmonic and the dielectric layer thickness of 1.67 QW correspond to the lower angular shifts in hue and thus the desired total of larger multilayer structures. Corresponds to the action of direction.

With reference to FIG. 6, FIG. 6A provides a graph of absorption-to-incident electromagnetic radiation wavelengths for the dielectric layer 110 and the absorption layer 120. As shown in this figure, the absorption layer 120 has a very low absorption rate at an incident wavelength of about 400 nm and a very high absorption at an incident wavelength in the range of 600 nm to 700 nm. Moreover, there is a relatively sharp increase in absorption between 400 nm and 600-700 nm. This provides significant wavelength blocking of light passing through the dielectric layer 110 that will be reflected by the core layer 100. This significant blockage corresponds to the graph shown in FIG. 6 (b). In the graph shown in FIG. 6B, the narrow band electromagnetic radiation is reflected in the 400 nm range. FIG. 6 (b) further shows that the shift at the center wavelength (400 nm) of the electromagnetic radiation in the reflected band when viewed from 0 ° and 45 ° is very low. It is understood that the reflected electromagnetic radiation in the narrow band has a width of less than 200 nm at the position measured at 50% reflectance relative to the maximum reflectance point / wavelength. In addition, the narrow reflected band has a width of less than 100 nm when measured at 75% of maximum reflectance for wavelengths of 400 nm.

With respect to multi-layered hue and chroma, FIG. 6 (c) shows very small changes in hue and chroma as a function of incident viewing angle. In addition, chroma is maintained between 58 and 60 for all angles between 0 ° and 45 °.

Here, moving to FIG. 7, another embodiment of the present invention is shown in FIG. 7A with reference number 20. The multilayer structure 20 has a second dielectric layer 130 extending over the outer surface of the absorption layer 120. FIG. 7 (b) provides a graph of the index of refraction for the various layers of structure 20, and FIG. 7 (c) shows the electric field as a function of thickness along structure 20 when the incident wavelength is 420 nm. Finally, FIG. 7 (d) provides a graph of the electric field as a function of the thickness over the multilayer structure 20 when the incident wavelength is 560 nm. As shown in FIGS. 7 (c) and 7 (d), the electric field is almost 0 when the wavelength is 420 nm, but is relatively large or high when the wavelength is 560 nm. Therefore, the reflected electromagnetic radiation in a narrow band in all directions is provided by the multilayer structure 20.

With reference to FIG. 8, FIG. 8 (a) shows the central wavelength (400 nm) of the reflected band of electromagnetic radiation from the structure shown in FIG. 9 (a) when viewed from 0 ° and 45 °. A graph of shifts is provided. The absorption-to-incident electromagnetic radiation wavelengths for the dielectric layer 110 and the absorption layer 120 are shown in FIG. 8 (b), and the hue and chroma are shown in FIG. 8 (c) as a function of the viewing angle.

Here, with reference to FIG. 9, schematic views of the two multilayer structures are shown with reference numbers 12 and 22. The multilayer structure 12 shown in FIG. 9A is essentially the same as that of Example 10 discussed above, except that another dielectric layer 110a and an absorption layer 120a are present on opposite sides of the core layer 100. Is the same as. Further, the multilayer structure 22 shown in FIG. 9B is a multilayer structure discussed above, except for another dielectric layer 110a, an absorbing layer 120a, and a dielectric layer 130a on opposite sides of the core layer 100. It is essentially the same as 20. Thus, the core layer 100 has both outer surfaces covered by the multilayer structure.

With reference to the graph plot shown in FIG. 9 (c), only the aluminum core layer (Al core), the aluminum core layer + ZnS dielectric layer (Al core + ZnS), and the five-layer aluminum core + ZnS + chromium structure (shown in Example 12). The reflectance vs. incident electromagnetic radiation wavelength is shown for such an Al core + ZnS + Cr (5L)) and a 7-layer aluminum core + ZnS + chromium + ZnS structure (Al core + ZnS + Cr + ZnS (7L)) as shown in Example 22. As shown in this figure, the seven-layer structure 22 with a pair of dielectric layers and an absorption layer in between provides electromagnetic radiation in a narrower and better defined reflection band compared to other structures. Will be done.

FIG. 10 shows a five-layer structure having a dielectric thickness that produces a second harmonic, a five-layer structure having a dielectric thickness that produces only the first harmonic, and only the first harmonic. An a * b * color map for a 7-layer structure with a dielectric layer thickness is provided. Compared to the lines showing other structures, the lines correspond to a 7-layer structure and the first harmonic corresponds to a low hue angle shift, as shown by the dotted circles showing the target color area in the figure. To do.

Created or simulated according to an embodiment of the present invention, with a layered structure of the present technology and two five-layered structures having a dielectric layer having an optical thickness greater than 3QW (hereinafter referred to as "5 layers> 3QW"). A comparison with a 7-layer structure having at least one dielectric layer having an optical thickness of less than 2QW (hereinafter referred to as "7 layers <2QW structure") is shown on the a * b * color map in FIG. Shown. As shown in the figure, the structure of the present technology and the 5-layer> 3QW structure are significantly improved by the 7-layer <2QW structure disclosed in the present specification. Especially chroma (

) Is larger for the 7-layer <2QW structure than for the 5-layer> 3QW structure. Further, the color shift (Δθ) is about half that of the 7-layer <2QW structure (Δθ ₁ ) as compared with the 5-layer> 3QW structure (Δθ ₂ ).

Table 1 below shows the numerical data for the 5 layer> 3QW structure and the 7 layer <2QW structure. It is understood that those skilled in the art will recognize that an increase of 1 or 2 points in chroma (C *) is a significant increase because the increase of 2 points is visually recognizable to the human eye. To. Therefore, the 6.02 point increase (16.1% increase) exhibited by the 7-layer <2QW structure is special. Further, the color shift for the 7-layer <2QW structure (15 °) is about half the color shift for the 5-layer> 3QW structure (29 °). Thus, given approximately equal lightness (L *) between the two structures, the 7-layer <2QW structure provides a significant and unexpected increase in color characteristics compared to prior art structures.

Another embodiment of the high chroma omnidirectional structural color multilayer structure is schematically shown by reference number 14 in FIG. 12 (a). The multilayer structure 14 is similar to Example 10 except for the additional absorption layer 105 and absorption layer 105a between the reflection layer 100 and the dielectric layers 110 and 110a, respectively. Another embodiment is shown by reference numeral 24 in FIG. 12 (b). This example is similar to Example 20 except that absorption layers 105 and 105a are added between the reflective layer or core layer 100 and the dielectric layers 110 and 110a, respectively.

Pigments from such multi-layer structures are manufactured as coatings on the web that have a sacrificial layer and a subsequent layer of material deposited using any type of deposition method or process known to those of skill in the art. obtain. The deposition methods or processes described above include electron beam deposition, sputtering, chemical vapor deposition, sol-gel treatment, and layer-by-layer treatment. When the multi-layer structure is deposited on the sacrificial layer, free-standing flakes with a surface dimension of 20 micron order and a thickness dimension of 0.3-1.5 micron order leave the multi-layer structure with the sacrificial layer removed. It can be obtained by grinding into flakes. Once flakes are obtained, the flakes are mixed with polymeric materials such as binders, additives and basecoat resins. This prepares an omnidirectional structural color paint.

The omnidirectional structural color paint has a color shift of less than 30 ° and minimal discoloration. Such a minimal tonal shift should be understood to be omnidirectional to the human eye. The sharpness of the hue is tan ^-1 (b * / a *), and in the equation, a * and b * are the color coordinates in the rab color system.

In summary, omnidirectional structural color pigments have a reflective layer or core layer, one or two dielectric layers, and one or two absorbing layers, where the wavelength of the control is peak reflection in the visible spectrum. At least one of the dielectric layers typically has a width greater than 0.1 QW but less than 2 QW, as determined by the rate by the target wavelength. Further, the peak reflectance is for the first harmonic reflectance peak. In some cases, the width of one or more dielectric layers is greater than 0.5 QW and less than 2 QW. In other cases, the width of one or more dielectric layers is greater than 0.5 QW and less than 1.8 QW.

The above examples and examples are for illustrative purposes only, changes and modifications will be apparent to those skilled in the art, and they fall within the scope of the present invention. Therefore, the scope of the present invention is defined by the claims.

Claims (11)

Including a multi-layer stack, the multi-layer stack
A core layer with a thickness between 50 nm and 200 nm ,
A dielectric layer extending over the core layer and
In between the interface extend over the dielectric layer and having an absorption layer having a thickness between 5nm and 20 nm,
The interface between the dielectric layer and the absorption layer is less than 25% | E | ² at the first incident electromagnetic wave length , where the square of the absolute value of the electric field E is | E | ² %. Yes , the second incident electromagnetic wave length has a relatively large | E | ² , and the second incident electromagnetic wave length is not equal to the first incident electromagnetic wave length.
The multi-layer stack has a single narrow reflection band with a full width at half maximum (FWHM) width of less than 200 nm in the visible spectrum when viewed from an angle between 0 ° and 45 ° that results in high chroma omnidirectional structural color. With minimal color change with a color shift of less than 30 °,
The dielectric layer has a thickness of 2 quarter waves (QW) or less of the central wavelength of the narrow reflection band.
The core layer is formed from a material selected from the group consisting of silver, copper, aluminum, gold and alloys thereof.
The dielectric layer comprises at least one of TiO ₂ , MgF ₂ , ZnS, HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and a combination thereof.
The absorbent layer is formed from a material selected from at least one of chromium, tantalum, tungsten, molybdenum, titanium, titanium nitride, niobium, cobalt, silicon, germanium, nickel, palladium, vanadium, iron oxide and alloys thereof. Ru,
High chroma omnidirectional structure Color multilayer structure. The core layer has a complex index of refraction represented by the formula RI ₁ = n ₁ + ik ₁ , n1 << k ₁ , where RI ₁ is the complex index of refraction and n ₁ is of the core layer. The highly chroma omnidirectional structural color multilayer structure according to claim 1, wherein k ₁ is the extinction coefficient of the core layer and i is √-1. The core layer, silver, copper, A aluminum, and is formed from a material selected from gold or Ranaru group, high chroma omnidirectional structural color multilayered structure of claim 2. The core layer is formed, et al or the aluminum, high chroma omnidirectional structural color multilayer structure of claim 3. It said dielectric _{layer, TiO 2, MgF 2, ZnS} , HfO 2, Nb 2 O 5, and Ta ₂ O comprises at least one of the _5, high chroma omnidirectional structural color multilayer structure of claim 4. The high chroma omnidirectional structural color multilayer structure according to claim 5 , wherein the dielectric layer is ZnS. The absorption layer has a complex refractive index represented by the formula RI ₂ = n ₂ + ik ₂ , n ₂ ≈ k ₂ , in which RI ₂ is the complex refractive index, and n ₂ is the dielectric layer of the dielectric layer. The high chroma omnidirectional structural color multilayer structure according to claim 6 , wherein k ₂ is a refractive index and is an extinction coefficient of the absorption layer. The absorbing layer is, chromium, tantalum, tungsten, molybdenum, titanium, niobium, cobalt, silicon, germanium, nickel, is formed palladium, and from a material selected from at least one of vanadium, claim 7 High chroma omnidirectional structure color multilayer structure. The absorbent layer, the chromium or we formed, high chroma omnidirectional structural color multilayer structure of claim 8. The high chroma omnidirectional structural color multilayer structure according to claim 9 , further comprising another dielectric layer extending over the outer surface of the absorption layer. The high chroma omnidirectional structural color multilayer structure according to claim 10 , further comprising another absorbing layer between the core layer and the dielectric layer.