JP6437817B2 - Red omnidirectional structural color made from metal and dielectric layers - Google Patents

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part (CIP) of US Patent Application No. 13 / 913,402, filed June 8, 2013, which is also a US patent filed February 6, 2013. No. 13 / 760,699, which is a CIP of U.S. Patent Application No. 13 / 572,071 filed on August 10, 2012, which is further filed on Feb. 5, 2011. US Patent Application No. 13 / 021,730, which is further CIP of US Patent Application No. 12 / 793,772, filed June 4, 2010, which is further February 18, 2009. This is the CIP of US patent application Ser. No. 12 / 388,395, which is a further application of US patent application Ser. No. 11 / 837,529 filed Aug. 12, 2007 (US Pat. No. 7,903,339). CIP It is. U.S. Patent Application No. 13 / 021,730, filed February 5, 2011, is also filed with U.S. Patent Application No. 11 / 837,529, filed Aug. 12, 2007 (U.S. Patent No. 7,903,339). It is also a CIP. US Patent Application No. 13 / 760,699 filed February 6, 2013 is also the CIP of US Patent Application No. 12 / 467,656 filed May 18, 2009. All of these are incorporated by reference in their entirety.

  The present invention relates to an omnidirectional structural color, specifically a red omnidirectional structural color provided by a multilayer stack having an absorber layer and a dielectric layer.

  Pigments made from multilayer structures are known. In addition, pigments that exhibit or result in high chroma 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 should be understood that the cost associated with the production of thin film multilayer pigments is proportional to the number of layers required. Thus, the costs associated with producing high saturation omnidirectional structural colors using multilayer stacks of dielectric materials can be prohibitive. Therefore, a high saturation omnidirectional structural color that requires a minimum number of thin film layers should be desirable.

A multilayer laminate is provided that provides a red omnidirectional structural color. The multilayer stack includes a reflector layer, a dielectric layer extending over the reflector layer, and an absorber layer extending over the dielectric layer. The dielectric layer combined with the reflector layer reflects more than 70% of incident white light having a wavelength greater than 550 nanometers (nm). Furthermore, the absorber layer absorbs more than 70% of incident white light having a wavelength of less than approximately 550 nm. Together, the reflector layer, the dielectric layer, and the absorber layer reflect (1) a narrow band (reflection peak or band) of visible electromagnetic radiation having a center wavelength between 550 and 700 nm and a width less than 200 nm. And (2) forming an omnidirectional reflector having a color shift of less than 100 nm when the omnidirectional reflector is viewed from an angle between 0 ^o and 45 ^o . In some examples, the narrow band width of the reflected visible electromagnetic radiation is less than 175 nm, preferably less than 150 nm, more preferably less than 125 nm, and even more preferably less than 100 nm.

  The reflector layer has a thickness between 50 and 200 nm and is made from a metal such as aluminum, silver, platinum, tin, or alloys thereof.

In some examples, the dielectric layer has an optical thickness between 0.1 and 2.0 quarter wavelengths (QW) of the desired reflection center wavelength. In other examples, the dielectric layer has an optical thickness that exceeds 2.0 QW of the desired reflection center wavelength. The dielectric layer also has a refractive index greater than 1.6 and is zinc sulfide (ZnS), titanium dioxide (TiO ₂ ), hafnium oxide (HfO ₂ ), niobium oxide (Nb ₂ O ₅ ), tantalum oxide ( Ta ₂ O ₅ ), combinations thereof, and the like. The dielectric layer can also contain a colored dielectric material such as iron oxide (Fe ₂ O ₃ ), copper oxide (Cu ₂ O), combinations thereof, and the like.

The absorption layer, also referred to herein as the absorber layer, may or may not be a colored layer, a selective absorption layer. For example, non-colored layers, i.e. non-selective absorber layers, can include layers made from chromium, silver, platinum, and the like. Alternatively, the absorbent layer can be a colored layer, a selective absorber layer made of copper, gold, their alloys, such as bronze and brass. In another alternative, the colored layer, the selective absorber layer contains a colored dielectric material, such as Fe ₂ O ₃ , Cu ₂ O, combinations thereof.

  It should be understood that the selective absorber layer is selected to absorb a desired range of wavelengths in the white light spectrum and reflect another desired range of the white light spectrum. For example, the selective absorber layer absorbs electromagnetic radiation having a wavelength corresponding to violet, blue, green, yellow (eg 400-550 nm) and further corresponds to red (ie 580 infrared (IR) (IR) ) Can be designed and manufactured to reflect range).

  In some examples, the multilayer stack includes a second dielectric layer in addition to the above-described dielectric layer (ie, the first dielectric layer), the second dielectric layer extending across the absorbing layer, In addition, the absorbing layer is disposed on the side opposite to the first dielectric layer. Furthermore, other embodiments are provided having a second absorbing layer, a third dielectric layer, and the like. However, the overall thickness of the multilayer laminate disclosed herein is less than 2 microns (μm), in some instances less than 1.5 μm, and in other examples less than 1.0 μm, In still another example, it is less than 0.75 μm.

FIG. 5 is a schematic representation of zero or near zero electric field points in a ZnS dielectric layer exposed to electromagnetic radiation (EMR) having a wavelength of 500 nm. Shows the relationship between the square of the absolute value of the electric field (| E | ² ) and the thickness of the ZnS dielectric layer shown in FIG. 1A when exposed to EMR having wavelengths of 300, 400, 500, 600, and 700 nm. It is a graph. 1 is a schematic illustration of a dielectric layer extending over a substrate or reflector layer and exposed to electromagnetic radiation at an angle θ relative to a direction perpendicular to the outer surface of the dielectric layer. FIG. 4 is a schematic illustration of a ZnS dielectric layer with a Cr absorber layer located at zero or near an electric field point in the ZnS dielectric layer with respect to an incident EMR having a wavelength of 434 nm. Relationship between reflectance (%) and reflected EMR wavelength for multilayer laminates without Cr absorber layer (eg, FIG. 1A) and multilayer laminates with Cr absorber layer (eg, FIG. 3A) exposed to white light It is a graph which shows. 2 is a graph showing first and second high harmonics exhibited by a ZnS dielectric layer (eg, FIG. 1A) extending over an Al reflector layer. Reflectivity for a multilayer stack having a ZnS dielectric layer extending across an Al reflector layer and a Cr absorber layer positioned within the ZnS dielectric layer to absorb the second harmonic shown in FIG. 5A It is a graph which shows the relationship between% and the EMR wavelength reflected. Reflectivity for a multilayer stack having a ZnS dielectric layer extending across an Al reflector layer and a Cr absorber layer located within the ZnS dielectric layer to absorb the first harmonic shown in FIG. 5A It is a graph which shows the relationship between% and a reflective EMR wavelength. It is a graph which shows the relationship between the square of the electric field which shows the angle dependence of the electric field of a Cr absorber layer, and the thickness of a dielectric material layer when exposed to incident light at 0 ^o and 45 ^o . Shows the relationship between the% absorbance by the Cr absorber layer and the reflected EMR wavelength when exposed to white light at angles of 0 ^o and 45 ^o to the normal to the outer surface (0 ^o is perpendicular to the surface). It is a graph. 1 is a schematic representation of a red omnidirectional structural color multilayer stack according to an embodiment of the present invention. 7B is a graph showing the relationship between the absorbance% of the Cu absorber layer shown in FIG. 7A and the reflected EMR wavelength when the multilayer laminate shown in FIG. 7A is exposed to white light at incident angles of 0 ^o and 45 ^o . . FIG. 6 is a graph showing a comparison of calculation / simulation data and experimental data of the relationship between reflectance% and reflected EMR wavelength of a red omnidirectional structural color multilayer laminate for proof of concept exposed to white light at an incident angle of 0 ^o. . 1 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention. 1 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention. 1 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention. 1 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention. 2 is a scanning electron microscope (SEM) image of flakes or pigments having a multilayer laminate structure according to an embodiment of the present invention. It is a SEM image of the cross section of each flake shown in FIG. Designed according to an embodiment of the present invention are manufactured, it is a schematic illustration of coated panel using a pigment having an orange having a hue of 36 ^o on a color map shown in FIG. 15D. 15D is a schematic illustration of a panel designed and manufactured in accordance with an embodiment of the present invention and painted with a pigment having a dark red color having a hue of 26 ^o on the color map shown in FIG. 15D. 15D is a schematic illustration of a panel designed and manufactured in accordance with an embodiment of the present invention and painted with a pigment having a bright pink color with a hue of 354 ^o on the color map shown in FIG. 15D. It is an a ^* b ^* color map using the CIELAB color space. It is the schematic of the 11-layer design goods used for the pigment of the paint represented by FIG. 1 is a schematic diagram of a seven-layer laminate according to an embodiment of the present invention. 1 is a schematic diagram of a seven-layer laminate according to an embodiment of the present invention. 1 is a schematic diagram of a seven-layer laminate according to an embodiment of the present invention. 1 is a schematic diagram of a seven-layer laminate according to an embodiment of the present invention. 15 is a graph showing a portion of an a ^* b ^* color map using the CIELAB color space, comparing saturation and hue shift between a conventional paint and the paint used to paint the panel shown in FIG. 15B. is there. It is a graph which shows the relationship between a reflectance and a wavelength about the 7-layer design goods by embodiment of this invention. It is a graph which shows the relationship between a reflectance and a wavelength about the 7-layer design goods by embodiment of this invention.

  A multilayer laminate is provided that provides an omnidirectional structural color, eg, a red omnidirectional structural color. As such, this multilayer laminate has applications as paint pigments, thin films that achieve desired colors, and the like.

  The multilayer stack that provides this omnidirectional structural color includes a reflector layer and a dielectric layer that extends across the reflector layer. The reflector layer and dielectric layer reflect more than 70% of incident white light having a wavelength greater than 550 nm. The thickness of the dielectric layer is predetermined so that more than 70% of the reflected incident white light is at a wavelength greater than or between 550 nm, 560 nm, 580 nm, 600 nm, 620 nm, 640 nm, 660 nm, 680 nm Please understand that you can. In other words, the thickness of the dielectric layer so that a specific color having the desired hue, saturation, and / or lightness on the map of the Lab color system is reflected and observed by the human eye. Can be selected and produced.

In some examples, the multilayer stack has a hue between 315 ^o and 45 ^{o in} the lab color space. The multilayer laminate has a hue shift of less than saturation and 30 ^o greater than 50. In other examples, the saturation is greater than 55, preferably greater than 60, and more preferably greater than 65, and / or the hue shift is less than 25 ^o , preferably less than 20 ^o , more preferably less than 15 ^o , Still more preferably, it is less than 10 ^° .

  An absorbing layer that absorbs more than 70% of the incident white light extends across the dielectric layer for all wavelengths substantially less than the wavelength corresponding to the desired reflection wavelength of the dielectric layer. For example, if the dielectric layer has a thickness that reflects more than 70% of the incident white light having a wavelength greater than 600 nm, the absorbing layer extending across the dielectric layer has an incident white light having a wavelength less than approximately 600 nm. Absorbs more than 70%. Thus, a sharp reflection peak having a wavelength in the red color space is obtained. In some examples, the reflector and dielectric layers reflect more than 80% of incident white light having a wavelength greater than 550 nm, and in other examples more than 90%. Also, in some examples, the absorber layer absorbs more than 80% of wavelengths less than about the wavelength corresponding to the desired reflection wavelength of the dielectric layer, and in other examples more than 90%.

  It should be understood that the term “approximately” in this context refers to ± 20 nm in some examples, ± 30 nm in other examples, ± 40 nm in yet other examples, and ± 50 nm in yet other examples.

The reflector layer, the dielectric layer, and the absorber layer reflect a narrow band of electromagnetic radiation (hereinafter referred to as the reflection peak or reflection band), and the central wavelength between 550 nm and the visible IR edge of the EMR spectrum. And an omnidirectional reflection having a reflection band having a width of less than 200 nm and a color shift of less than 100 nm when the omnidirectional reflector is exposed to white light and viewed from an angle between 0 ^o and 45 ^o Form the body. This color shift can be in the form of a shift in the center wavelength of the reflection band, or alternatively in the form of a shift in the UV side ridge of the reflection band. For the purposes of the present invention, the width of the reflection band of electromagnetic radiation is defined as the width of the reflection band at one half of the reflection height of the maximum reflection wavelength in the visible spectrum. Furthermore, the narrow band of reflected electromagnetic radiation, ie the “color” of the omnidirectional reflector, has a hue shift of less than 25 ^° . In some examples, the reflector layer has a thickness between 50 and 200 nm and is made of or contains a metal such as aluminum, silver, platinum, tin, alloys thereof.

  For a dielectric layer that extends across the reflector layer, the dielectric layer has an optical thickness between 0.1 QW and 2.0 QW. In some examples, the dielectric layer has an optical thickness between 0.1 QW and 1.9 QW, while in other examples, the dielectric layer has a thickness between 0.1 QW and 1.8 QW. In yet another example, the dielectric layer is less than 1.9 QW, eg, less than 1.8 QW, less than 1.7 QW, less than 1.6 QW, less than 1.5 QW, less than 1.4 QW, less than 1.3 QW, less than 1.2 QW Or an optical thickness of less than 1.1 QW. Alternatively, the dielectric layer has an optical thickness greater than 2.0QW.

The dielectric layer has a refractive index greater than 1.60, 1.62, 1.65, or 1.70, for example, ZnS, TiO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , these It can be made from dielectric materials such as combinations. In some examples, the dielectric layer is a colored layer, a selective dielectric layer made of a colored dielectric material, such as Fe ₂ O ₃ , Cu ₂ O, for example. For purposes of the present invention, the term “colored dielectric material” or “colored dielectric layer” refers to a dielectric material or dielectric that transmits only a portion of incident white light while reflecting another portion of white light. Refers to the body layer. For example, the colored dielectric layer can transmit electromagnetic radiation having a wavelength between 400 nm and 600 nm and can reflect wavelengths above 600 nm. As such, the colored dielectric material or colored dielectric layer has an orange, red, and / or reddish orange appearance.

In addition to the dielectric layer, the omni-directional reflector can include a selective absorber layer having a thickness between 5 and 200 nm. In some instances, a colored absorber layer replaces or replaces the absorber layer. Similar to the above description, the selective absorber layer absorbs light having a wavelength related to violet, blue, yellow, green, and the like, and corresponds to orange, red, and / or reddish orange. Can be reflected. In some examples, the colored absorber layer contains or is made of a colored metal such as copper, gold, alloys thereof, such as bronze, brass. In yet another example, the colored absorber layer may contain or be made of a colored dielectric material, such as Fe ₂ O ₃ , Cu ₂ O.

  The position of the absorber layer is such that a zero or near-zero energy interface exists between the absorber layer and the dielectric layer. In other words, the dielectric layer has a thickness such that a zero or near zero energy field is located at the dielectric layer-absorber layer interface. It should be understood that the thickness of the dielectric layer in the presence of zero or near zero energy field is a function of the incident EMR wavelength. Furthermore, wavelengths that correspond to zero or near-zero electric fields will be transmitted through the dielectric layer-absorber layer interface, whereas wavelengths that do not correspond to zero or near-zero electric fields at that interface will not pass through it. I want you to understand that. Thus, the thickness of the dielectric layer is such that the desired wavelength of incident white light is transmitted through the dielectric layer-absorber layer interface, reflected from the reflector layer, and then transmitted back through the dielectric layer-absorber layer interface. Designed and manufactured to. Similarly, the thickness of the dielectric layer is manufactured so that unwanted wavelengths of incident white light are not transmitted through the dielectric layer-absorber layer interface.

  Given the above, wavelengths that do not correspond to the desired zero or near-zero electric field interface are absorbed by the absorber layer and are therefore not reflected. In this way, a desirable “sharp” color, also known as structural color, is provided. Furthermore, the thickness of the dielectric layer is such that a desired first harmonic and / or second harmonic harmonic reflection occurs to give the surface a red color that also has an omnidirectional appearance.

  The multi-layer stack can include a second dielectric layer in addition to the dielectric layer described above (also known as the first dielectric layer), which second dielectric layer extends across the absorber layer. . Further, the second dielectric layer is disposed on the opposite side of the dielectric layer first described for the absorber layer.

  FIG. 1A is a schematic diagram of a ZnS dielectric layer extending across an Al reflector layer with respect to the thickness of the dielectric layer and the electric field point at or near zero. The ZnS dielectric layer has a total thickness of 143 nm and there is an energy point at or near zero for incident electromagnetic radiation having a wavelength of 500 nm 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 EMR having a wavelength of 500 nm. In addition, FIG. 1B provides a graph showing the energy field across the ZnS dielectric layer for a number of different incident EMR wavelengths. As shown in this graph, the dielectric layer has a zero electric field for a wavelength of 500 nm at a thickness of 77 nm, but at a thickness of 77 nm for EMR wavelengths of 300, 400, 600, and 700 nm. Has a non-zero electric field.

  Without being bound by theory, the calculation of the thickness of zero or near zero energy points for a dielectric layer, such as that shown in FIG. 1A, is discussed below.

Referring to Figure 2, shows on the refractive index substrate or core layer 2 having an n _s, the total thickness "D", the incremental thickness "d", and a dielectric layer 4 having a refractive index "n". Incident light strikes the outer surface 5 of the dielectric layer 4 at an angle θ with respect to a line 6 perpendicular to the outer surface 5 and is reflected from the outer surface 5 at the same angle. Incident light passes through the outer surface 5, enters 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 the case of 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
And for p-polarized light,
Can be expressed as
Where k = 2π / λ, where λ is the desired wavelength to be reflected. Α = n _s sin θ _s (where “s” corresponds to the substrate in FIG. 1), and
Is the dielectric constant of the layer as a function of z. So for s-polarized light,
For p-polarized light,
It is.

It should be understood that the variation of the electric field along the Z direction of the dielectric layer 4 can be estimated by calculating the unknown parameters u (z) and v (z). However, the fluctuation is
Can be shown with

Of course, “i” is the square root of −1. boundary condition
And relations,
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 = n cos θ _F (8)
For p-polarized light, q = n / cos θ _F (9)
φ = k · n · dcos (θ _F ) (10)
U (z) and v (z) using
as well as
Can be expressed as

Therefore, for s-polarized light
However, φ = k · n · cos (θ _F ) and p-polarized light
However,
It is.

Thus, for a simple situation of θ _F = 0, ie normal incidence, φ = k · n · d and α = 0, ie
This makes it possible to solve the equation for the thickness “d”, that is, for the position or location in the dielectric layer where the electric field is zero.

  Referring now to FIG. 3, using Equation 19, there is a zero or near zero electric field point at 70 nm in the ZnS dielectric layer shown in FIG. 1A when exposed to EMR having a wavelength of 434 nm. (Instead of 77 nm for 500 nm) was calculated. Furthermore, a Cr absorber layer having a thickness of 15 nm was inserted at a thickness of 70 nm from the Al reflector layer to give a ZnS-Cr interface with an electric field of zero or near zero. Such a structure of the present invention allows light having a wavelength of 434 nm to pass through the Cr—ZnS interface, but absorbs light having no wavelength of 434 nm. In other words, the Cr-ZnS interface has an electric field of zero or near zero for light having a wavelength of 434 nm, so that 434 nm light 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, and thus such light is absorbed by the Cr absorber layer and / or the Cr—ZnS interface. , Not reflected by the Al reflector layer.

  It should be understood that a certain percentage of light within the desired 434 nm +/− 10 nm range will pass through the Cr—ZnS interface. However, it should also be understood that such a narrow band of reflected light, eg 434 nm +/− 10 nm, also provides a clear structural color to the human eye.

  The result of the Cr absorber layer in the multilayer laminate in FIG. 3 is shown in FIG. 4 showing the relationship between the reflectance% and the reflected EMR wavelength. As shown by the dotted line corresponding to the ZnS dielectric layer shown in FIG. 3 without the Cr absorber layer, a narrow reflection peak is present at about 400 nm, but a much broader peak is present at about 550+ nm. In addition to this, there is still a significant amount of reflected light in the 500 nm wavelength region. As such, there are double peaks that prevent the multilayer stack from having or exhibiting a structural color.

  In contrast, the solid line in FIG. 4 corresponds to the structure shown in FIG. 3 where the Cr absorber layer is present. As shown in the figure, there is a sharp peak at approximately 434 nm, and the Cr absorber layer provides a sharp decrease in reflectivity for wavelengths above 434 nm. It can be seen that the sharp peak represented by the solid line is visible as a sharp / structural color. FIG. 4 also shows where the reflection peak or band width is measured. That is, the width of the band is measured at 50% reflectivity of the maximum reflection wavelength, also known as the full width at half maximum (FWHM).

  With regard to the omnidirectional behavior of the multilayer structure shown in FIG. 3, the thickness of the ZnS dielectric layer can be designed or set to provide only the first harmonic of the reflected light. This is sufficient for the “blue” color, but it turns out that additional care is needed to produce the “red” color. For example, red angle-independent control requires a thicker dielectric layer, which in turn leads to sophisticated harmonic designs, i.e. difficult to avoid due to the presence of second and possible third harmonics. It is. The dark red hue space is very narrow. Thus, the red multilayer stack has a higher angular variation.

In order to overcome the higher red angle variation, this application discloses a unique and novel design / structure that gives a red color that is not affected by the angle. For example, FIG. 5A shows a dielectric layer that exhibits first and second harmonics for incident white light when the outer surface of the dielectric layer is viewed from 0 ^o and 45 ^o . As this graph shows, the low angular dependence (small Δλ _c ) is caused by the thickness of the dielectric layer, but such multilayer stacks are blue (first harmonic) and red (second harmonic). ) And therefore not suitable for the desired “red only” color. Therefore, a concept / structure has been developed that uses the absorber layer to absorb unwanted harmonic sequences. FIG. 5A also shows an example of the position of the reflection band center wavelength (λ _c ) for a given reflection peak and the dispersion or deviation (Δλ _c ) of the center wavelength when the sample is viewed from 0 ^o and 45 ^o. .

Referring now to FIG. 5B, the second harmonic shown in FIG. 5A is absorbed by the Cr absorber layer at the appropriate dielectric layer thickness (eg, 72 nm), resulting in a clear blue color. More importantly for the present invention, FIG. 5C shows that red is obtained by absorbing the first harmonic with a Cr absorber layer at another dielectric layer thickness (eg, 125 nm). Show. However Figure 5C also relates to the use of Cr the absorber layer further exceeds the desired angle dependence by the multilayer stack, indicating that cause significant △ lambda _c ie exceeding the desired △ lambda _c.

The relatively large shift in red λ _c compared to blue is that the dark red hue space is very narrow, and that the Cr absorber layer absorbs wavelengths associated with non-zero electric fields, ie the electric field is zero or zero. It can be seen that the Cr absorber does not absorb light when the value is close to. As such, FIG. 6A shows that the zero point or non-zero point is different for different wavelengths of light. Such factors cause the difference between the angle-dependent absorbances shown in FIG. 6B, that is, the absorbance curves of 0 ^o and 45 ^o . Therefore, in order to further refine the design of the multilayer stack and the performance unaffected by the angle, an absorber layer that absorbs, for example, blue is used regardless of whether the electric field is zero or not.

Specifically, FIG. 7A shows a multilayer stack in which a Cu absorber layer extends over a dielectric ZnS layer instead of a Cr absorber layer. The result of using such a “colored” or “selective” absorber layer is shown in FIG. 7B. This figure shows a much “no gap” arrangement of the 0 ^o and 45 ^o absorbance lines for the multilayer stack shown in FIG. 7A. As such, the comparison between FIGS. 6B and 7B shows a significant improvement in the angular dependence of absorbance when using a selective absorber layer rather than a non-selective absorber layer.

  Based on the above, a multilayer laminate structure for proof of concept was designed and manufactured. In addition, the results of calculations / simulations and actual experimental data for proof-of-concept samples were compared. Specifically, and as shown by the graph plot in FIG. 8, a bright red color is produced (wavelengths above 700 nm are generally not visible to the human eye), and calculations / simulations and experiments obtained from actual samples Very good agreement was obtained with the optical data from In other words, calculation / simulation can be used to simulate the results of a multilayer laminate design and / or prior art multilayer laminate according to one or more embodiments of the present invention, and / Or simulated.

  A list of simulated and / or actually created multilayer laminate samples is provided in Table 1 below. As shown in the table, the design product of the present invention disclosed in the present specification includes at least five different layered structures. In addition, these samples were simulated and / or made from a wide range of materials. Samples were obtained that exhibited high saturation, low hue shift, and excellent reflectance. The 3 layer and 5 layer samples also have a total thickness between 120 and 200 nm, the 7 layer sample has a total thickness between 350 and 500 nm, and the 9 layer sample has a total thickness between 440 and 500 nm. The 11-layer sample had a total thickness between 600 and 660 nm.

  With respect to the actual arrangement order of the layers, FIG. The omnidirectional reflector 10 includes a reflector layer 100, a dielectric layer 110 extending over the reflector layer 100, and an absorber layer 120 extending over the dielectric layer 110. It should be understood that another dielectric layer and another absorber layer can be placed on the opposite side of the reflector layer 100 to provide a five layer design.

  Reference numeral 20 in FIG. 10 indicates a seven-layer design in which another dielectric layer 130 extends across the absorber layer 120 such that another dielectric layer 130 is disposed opposite the dielectric layer 110 with respect to the absorber layer 120. Show half of the goods.

  FIG. 11 shows half of the nine-layer design where the second absorber layer 105 is located between the reflector layer 100 and the dielectric layer 110. Finally, FIG. 12 shows half of an 11-layer design in which another absorber layer 140 extends over the dielectric layer 130 and yet another dielectric layer 150 extends over the absorber layer 140.

FIG. 13 shows a scanning electron microscope (SEM) image of a plurality of pigments having a multilayer structure according to an embodiment of the present invention. FIG. 14 is an SEM image of one of the higher magnification pigments showing this multilayer structure. Such pigments were used to create three different red paints, which were then applied to three panels for testing. Since the actual picture of the panel appears gray / black when printed and copied, and also in black and white (back and white), FIGS. 15A-15C are schematics of the actual painted panel. On the color map shown in FIG. 15D, FIG. 15A represents an orange color with a hue of 36 ^o , FIG. 15B represents a dark red color with a hue of 26 ^o , and FIG. 15C represents a light pink color with a hue of 354 ^o . Represent. Also, the dark red panel depicted in FIG. 15B had a lightness L ^{* of} 44 and a chroma C ^* of 67.

  FIG. 15E is a schematic illustration of an 11-layer design depicting the pigments used to apply to the panels shown in FIGS. With respect to various layer thickness examples, Table 2 provides the actual thickness for each of its corresponding multilayer laminate / pigments. As the thickness values in Table 2 indicate, the total thickness of the 11-layer design is less than 2 μm and can also be less than 1 μm.

  It can be seen that 7-layer designs and 7-layer design multilayer laminates can be used to create such pigments. Examples of four types of seven-layer multilayer laminates are shown in FIGS. FIG. 16A shows (1) a reflector layer 100, (2) a pair of dielectric layers 110 extending across the reflector layer 100, and arranged facing each other on both sides, and (3) a pair of dielectric layers 110. 7 shows a seven-layer laminate having a pair of selective absorber layers 120a extending over the outer surface, and (4) a pair of dielectric layers 130 extending over the outer surface of the pair of selective absorber layers 120a.

Of course, the thickness of the dielectric layer 110 and the selective absorber layer 120a is such that the interface between the selective absorber layer 120a and the dielectric layer 110 and the interface between the selective absorber layer 120a and the dielectric layer 130 are the colors shown in FIG. The thickness is such that it shows an electric field of zero or near zero for the desired light wavelength in the pink-red-orange gamut (315 ^o <hue <45 ^o and / or 550 nm <λ _c <700 nm). Thus, the desired red light passes through layers 130-120a-110, reflects off layer 100, and returns through layers 110-120a-130. In contrast, non-red light is absorbed by the selective absorber layer 120a. Furthermore, the selective absorber layer 120a has an absorbance that is not affected by the angle with respect to non-red light, as discussed above and as shown in FIGS.

It can be seen that the thickness of the dielectric layer 100 and / or 130 is such that the reflectance of red light by the multilayer stack is omnidirectional. Omnidirectional reflection is measured or determined by the small Δλ _c of the reflected light. For example, in some examples, Δλ _c is less than 120 nm. In other examples, Δλ _c is less than 100 nm. In still other examples, Δλ _c is less than 80 nm, preferably less than 60 nm, even more preferably less than 50 nm, and even more preferably less than 40 nm.

Omnidirectional reflection can also be measured by a low hue shift. For example, the hue shift of a pigment produced from a multilayer laminate according to an embodiment of the present invention is 30 ^o or less as shown in FIG. 17 (see Δθ ₁ ), and in some examples the hue shift is 25 ^o or less, Preferably it is 20 ^o or less, more preferably 15 ^o or less, and even more preferably 10 ^o or less. In contrast, conventional pigments exhibit a hue shift of 45 ^o or more (see Δθ ₂ ).

  FIG. 16B shows (1) a selective reflector layer 100a, (2) a pair of dielectric layers 110 extending across the reflector layer 100a, and disposed facing each other on both sides thereof, and (3) the pair of dielectric layers 110. 7 shows a seven-layer laminate having a pair of selective absorber layers 120a extending over the outer surface of the pair and (4) a pair of dielectric layers 130 extending over the outer surface of the pair of selective absorber layers 120a.

  FIG. 16C shows (1) a selective reflector layer 100a, (2) a pair of dielectric layers 110 extending across the reflector layer 100a, and disposed facing each other on both sides thereof, and (3) the pair of dielectric layers 110. 7 shows a seven-layer laminate having a pair of non-selective absorber layers 120 extending over the outer surfaces of the pair and (4) a pair of dielectric layers 130 extending over the outer surfaces of the pair of absorber layers 120.

  FIG. 16D shows (1) a reflector layer 100, (2) a pair of dielectric layers 110 extending across the reflector layer 100 and arranged facing each other on both sides thereof, and (3) the pair of dielectric layers 110. 7 shows a seven-layer stack having a pair of absorber layers 120 extending over the outer surface and (4) a pair of dielectric layers 130 extending over the outer surface of the pair of selective absorber layers 120.

Referring now to FIG. 18, the relationship between reflectance% and reflected EMR wavelength for a seven-layer omnidirectional reflector when exposed to white light at angles of 0 ^o and 45 ^o relative to the reflector surface. The graph of is shown. As this graph shows, both the 0 ^o and 45 ^o curves show very low reflectivity, eg, less than 10%, provided by the omni-directional reflector for wavelengths below 550 nm. However, as this curve shows, this reflector provides a significant increase in reflectivity at wavelengths between 560 and 570 nm, reaching a maximum of nearly 90% at 700 nm. It should be understood that the portion or region of the graph on the right hand side (IR side) of the curve represents the IR portion of the reflection band provided by this reflector.

The significant increase in reflectivity provided by this omni-directional reflector is characterized by a ridge on the UV side of each curve that extends from a low reflectivity part at wavelengths below 550 nm to a high reflectivity part, eg> 70%. . The straight line portion 200 of the UV side ridge line is inclined at an angle (β) exceeding 60 ^° with respect to the x-axis, and has a length L of approximately 40 and an inclination of 1.4 on the reflectivity axis. In some examples, the linear portion is inclined at an angle greater than 70 ^° with respect to the x axis, while in other examples β is greater 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. Further, as shown in FIG. 18, the center wavelength λ _c of the visible reflection band is defined as a wavelength that is an equal distance between the UV side ridge line of the reflection band and the IR spectrum ridge line in the visible FWHM.

  The term “visible FWHM” means the width of the reflection band between the UV side ridge of the curve and the ridge of the IR spectral range beyond which the reflectivity provided by the omni-directional reflector is invisible to the human eye It should be understood that Thus, the design of the present invention and the multilayer laminate disclosed herein use the non-visible IR portion of the electromagnetic radiation spectrum to obtain a sharp or structural color. In other words, despite the fact that the omnidirectional reflectors disclosed herein may reflect a much wider band of electromagnetic radiation that extends to the IR region, The invisible IR portion of the electromagnetic radiation spectrum is successfully used to obtain a narrow band of reflected visible light.

Referring now to FIG. 19, the relationship between% reflectance and wavelength for another 7-layer designed omnidirectional reflector when exposed to white light at angles of 0 ^o and 45 ^o relative to the reflector surface. The graph of is shown. In addition, a definition or characterization of the omnidirectional properties obtained by the omnidirectional reflector disclosed herein is provided. Specifically, and as shown in the figure, when the reflection band produced by the reflector of the present invention has the highest value or peak, each curve is defined as the center wavelength defined as the wavelength exhibiting or becoming the maximum reflectivity. (Λ _c ). The term maximum reflection wavelength for λ _c can also be used.

As shown in FIG. 19, when the outer surface of the omni-directional reflector is observed from an angle 45 ^o (λ _c (45 ^o )), that is, when the outer surface is inclined 45 ^{o with} respect to the eyes of the person viewing the surface, Compared to observing the surface from 0 ^o (λ _c (0 ^o )), that is, from an angle perpendicular to the surface, there is a shift or displacement of λ _c . This λ _c deviation (Δλ _c ) provides a measure of the omnidirectional characteristics of the omnidirectional reflector. Of course, a zero shift, i.e. no shift, should be a perfect omni-directional reflector. However, the omnidirectional reflector disclosed herein can provide a Δλ _c of less than 100 nm, as if the surface of the reflector did not change color, as if it was in the human eye. From a practical point of view, it can appear as if the reflector is omnidirectional. In some examples, the omni-directional reflectors disclosed herein have a Δλ _c of less than 75 nm, in other examples a Δλ _c of less than 50 nm, and in other examples a Δλ of less than 25 nm. _c , and in still other examples, Δλ _c of less than 15 nm can be achieved. Such deviations in Δλ _c can be represented by a graph showing the relationship between the actual reflectivity and wavelength of the reflector, and / or if the material and layer thickness are otherwise known, model the reflector. Can be determined by.

Another definition or characterization of the omnidirectional characteristics of the reflector can be determined by the shift of the side edges of a given set of angular reflection bands. For example, the measure of the omnidirectional characteristic of the omnidirectional reflector is the deviation or displacement (Δ) of the UV side ridgeline of the reflectance from the omnidirectional reflector observed from 0 ^o (S _L (0 ^o )). S _L ) is obtained by comparing the deviation or displacement of the UV side ridgeline of the reflectance by the same reflector observed from 45 ^o (S _L (45 ^o )). Furthermore, using ΔS _L as a measure of omnidirectionality corresponds to a band of reflectivity similar to that shown in FIG. 18 for use of Δλ _c , ie, the maximum reflected wavelength not within the visible range. May be preferred for reflectors that provide a reflection band with a peak that (see FIG. 18). The UV side ridge shift (ΔS _L ) can be measured and / or measured in the visible FWHM.

Of course, the zero shift, ie no deviation (ΔS _L = 0 nm), should characterize a perfect omnidirectional reflector. However, the omnidirectional reflectors disclosed herein can provide a ΔS _L of less than 100 nm, as if the surface of the reflector did not change color as if it were in the human eye. Therefore, from a practical point of view, the reflector can appear as if it is omnidirectional. In some examples, the omnidirectional reflector disclosed herein has a ΔS _{L of} less than 75 nm, in other examples a ΔS _{L of} less than 50 nm, and in other examples a ΔS _{L of} less than 25 nm, In still another example, Δλ _c of less than 15 nm can be realized. Such a shift in Δλ _c is produced by a graph showing the relationship between the actual reflectivity and wavelength of the reflector and / or otherwise modeling the reflector if the material and layer thickness are known. Can be decided.

  The method of manufacturing a multilayer laminate disclosed herein can be any method or process known to those skilled in the art, or one or more methods not yet known to those skilled in the art. Common known methods include sol-gel methods, layer-by-layer methods, and wet methods such as spin coating. Other known dry methods include physical vapor deposition methods such as sputtering, chemical vapor deposition, and electron beam evaporation.

  The multilayer laminate disclosed herein can be used for most arbitrary colored coatings such as paint pigments, thin films applied to surfaces.

  The above examples and embodiments are for illustrative purposes only, and variations and modifications thereof should be apparent to those skilled in the art and still fall within the scope of the invention. Accordingly, the scope of the invention is defined by the claims and all equivalents thereof.

Claims (10)

Reflector layer,
A dielectric layer extending across the reflector layer, wherein the reflector layer and the dielectric layer reflect more than 70% of incident white light having a wavelength greater than 550 nm; and over the dielectric layer A selective absorption layer that spreads, comprising a selective absorption layer that absorbs more than 70% of the incident white light having a wavelength of less than 550 nm;
The reflector layer, the dielectric layer, and the selective absorption layer form an omnidirectional reflector, and the omnidirectional reflector has a center wavelength between 550 and 700 nm, a width of less than 200 nm, and the omnidirectional Reflecting a narrow band of visible electromagnetic radiation having a color shift of less than 60 nm when viewed from an angle between 0 and 45 ^o , said omnidirectional reflector exhibiting a red omnidirectional structural color ;
Multi-layer laminate that displays red omnidirectional structural color.   The multilayer laminate according to claim 1, wherein the reflector layer has a thickness of 50 to 200 nm. Said dielectric layer has a thickness of 30 to 300 nm, the multilayer laminate according to claim 1 or 2. The multilayer laminate according to any one of claims 1 to 3 , wherein the selective absorption layer has a thickness of 20 to 80 nm. The omnidirectional reflector has a total thickness of less than 1 [mu] m, the multilayer laminate according to any one of claims 1 to 4. The center wavelength is 30 ^o The multilayer laminate according to any one of claims 1 to 5, having a hue shift of less than 6. The multilayer laminate according to any one of claims 1 to 6, wherein the dielectric layer has an optical thickness of more than 0.1 QW and less than 3.0 QW. The dielectric layer has a refractive index greater than 1.6, and ZnS, TiO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ And a dielectric material selected from the group consisting of these, or the dielectric layer is Fe ₂ O ₃ , Cu ₂ The multilayer laminate according to any one of claims 1 to 7, comprising a colored dielectric material selected from the group consisting of O and combinations thereof. The selective absorption layer contains a colored metal selected from the group consisting of Cu, Au, Zn, Sn, and alloys thereof, or the selective absorption layer is Fe ₂ O ₃ , Cu ₂ The multilayer laminate according to any one of claims 1 to 8, comprising a colored dielectric material selected from the group consisting of O and combinations thereof. The dielectric layer further includes a second dielectric layer in addition to the dielectric layer, the second dielectric layer extends over the selective absorption layer, and the second dielectric layer is the dielectric with respect to the selective absorption layer. Placed on the opposite side of the layer,
The multilayer laminate according to any one of claims 1 to 9, wherein the reflector layer, the dielectric layer, the selective absorption layer, and the second dielectric layer form the omnidirectional reflector.