JP2020037692A - Omnidirectional high chroma red structural colors - Google Patents

Abstract

To provide multilayer interference thin films that have a reduced number of layers and reflect high chroma red structural colors in an omnidirectional manner.SOLUTION: There is provided a multilayer thin film that reflects an omnidirectional high chroma red structural color. The multilayer thin film may include a reflector layer, at least one absorber layer extending across the reflector layer, and an outer dielectric layer extending across the at least one absorber layer. The multilayer thin film reflects a single narrow band of visible light when exposed to white light, and the outer dielectric layer has a thickness less than or equal to 2.0 quarter wave (QW) of a center wavelength of the single narrow band of visible light.SELECTED DRAWING: None

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part (CIP) of U.S. Patent Application Nos. 14 / 793,117, 14 / 793,123 and 14 / 793,133. U.S. Patent Applications Nos. 14 / 793,117, 14 / 793,123 and 14 / 793,133 were all filed on July 7, 2015 and filed on January 28, 2015. No. 14 / 607,933, which is incorporated herein by reference in its entirety.

  The present specification relates generally to multilayer interference thin films for exhibiting high chroma red structure colors, and more specifically, to multilayer interference thin films for exhibiting high chroma red structure colors in all directions.

  Pigments made from multilayer structures are known. In addition, pigments exhibiting or providing a high chroma omnidirectional structural color are also known. Such pigments require as many as 39 dielectric layers to achieve the desired color characteristics, and the cost of producing a multilayer pigment is proportional to the number of thin film layers. Therefore, the production of high chroma omnidirectional structural colors using multilayer thin films of dielectric material is too costly. The design of red pigments is an additional hurdle for pigments of other colors, such as blue and green. Specifically, angle-independent control to obtain red color requires higher harmonic designs, i.e., thicker dielectric layers that result in the presence of second and possibly third harmonics. Difficult. Further, the hue space in the Lab color space for dark red is very narrow, and the multilayer thin film showing red shows higher angular fluctuation.

  Therefore, there is a need for an alternative multilayer interference thin film that has a small number of layers and reflects high chroma red structural colors in all directions.

  In one embodiment, the multi-layer interference thin film reflecting the omni-directional high chroma red structural color comprises a reflector layer, at least one absorber layer extending over the reflector layer, and extending over the at least one absorber layer. And an outer dielectric layer. The outer dielectric layer has a thickness no greater than 2.0 quarter wavelength (QW) of the center wavelength of a single narrow band of visible light reflected by the multilayer thin film. A single narrow band of visible light has a visible full width at half maximum (visible FWHM) width of less than 300 nanometers (nm), a red color in the Lab color space of 0 ° to 30 °, and perpendicular to the outer surface of the outer dielectric layer. When the multilayer thin film is observed at an angle of 0 to 45 ° with respect to the direction, it has a hue shift of less than 30 ° in the Lab color space.

In another embodiment, the omnidirectional high chroma red structural color multilayer thin film for reflecting red, which has no change in appearance to the human eye when viewed at various angles, comprises a reflector layer and the reflector layer. A multilayer thin film having a dielectric absorber layer extending over the entire surface, a transparent absorber layer extending over the dielectric absorber layer, and an outer dielectric layer extending over the transparent absorber layer may be included. The outer dielectric layer has a thickness equal to or less than 2.0 QW of the central wavelength of a single narrow band of visible light reflected by the multilayer thin film. A single narrow band of visible light has a visible FWHM width of less than 200 nanometers, a red of 0-30 ° in the Lab color space, and 0-45 with respect to a direction perpendicular to the outer surface of the outer dielectric layer. When the multilayer thin film is observed at an angle of °, it has a hue shift of less than 30 ° in the Lab color space. The dielectric absorber layer is made of at least one of an oxide and a nitride, and has a thickness of 5 to 500 nm. The transparent absorber layer is made of chromium (Cr), germanium (Ge), nickel (Ni), stainless steel, titanium (Ti), silicon (Si), vanadium (V), titanium nitride (TiN), tungsten (W), molybdenum (Mo), has been made from at least one of niobium (Nb) and iron oxide _(Fe 2 _{O 3),} having a thickness of 5 to 20 nm.

  These features and further features exhibited by the embodiments described below will be more fully understood in view of the following detailed description in conjunction with the drawings.

  The embodiments illustrated in the drawings are exemplary and illustrative in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of the exemplary embodiments can be understood when read in conjunction with the accompanying drawings, wherein like structures are designated by like reference numerals.

FIG. 1A illustrates a dielectric layer (D) extending across a reflector layer (R) used in the design of an omnidirectional high chroma red structural color multilayer thin film according to one or more embodiments shown and described herein. Is shown. FIG. 1B illustrates a semiconductor absorber layer (SA) extending across a reflector layer (R) used in the design of an omnidirectional high chroma red structural color multilayer thin film according to one or more embodiments shown and described herein. 3) shows a multilayer thin film having the following formula: FIG. 1C illustrates a dielectric absorber layer (R) extending across a reflector layer (R) used in the design of an omnidirectional high chroma red structural color multilayer thin film according to one or more embodiments shown and described herein. 3 shows a multi-layer thin film having DA). FIG. 2 shows reflection characteristics in the Lab color space of the multilayer thin films shown in FIGS. 1A to 1C. FIG. 3A graphically illustrates the saturation and hue values as a function of the thickness of the dielectric layer (D) for the multilayer thin film shown in FIG. 1A. FIG. 3B graphically illustrates the saturation and hue values as a function of semiconductor absorber layer (SA) thickness for the multilayer thin film shown in FIG. 1B. FIG. 3C graphically illustrates the saturation and hue values as a function of the thickness of the dielectric absorber layer (DA) for the multilayer thin film shown in FIG. 1C. FIG. 4 shows a multilayer thin film having a dielectric layer extending across a substrate layer and exposed to electromagnetic radiation at an angle θ with respect to a direction perpendicular to the outer surface of the dielectric layer. FIG. 5 graphically illustrates the value of the electric field (| electric field | ² ) as a function of layer thickness for two multilayer films exposed to light at a wavelength of 550 nm. One of the multilayer thin films includes a dielectric absorber layer extending over the reflector layer, a transparent absorber layer extending over the dielectric absorber layer, and a dielectric layer extending over the transparent absorber layer (R / DA / TA / D), and the other multilayer thin film includes a dielectric absorber layer extending over the reflector layer, and a dielectric layer extending over the dielectric absorber layer. (R / DA / D). FIG. 6 graphically illustrates the electric field (| electric field | ² ) as a function of layer thickness for (R / DA / TA / D) multilayer thin films when exposed to light at wavelengths between 550 nm and 650 nm. FIG. 7 illustrates a multilayer thin film according to one or more embodiments shown and described herein. FIG. 8 illustrates a multilayer thin film according to one or more embodiments shown and described herein. FIG. 9 shows white light on a multilayer thin film according to one or more embodiments shown and described herein, observed at 0 ° and 45 ° relative to a direction perpendicular to the outer surface of the multilayer thin film. The reflectance (%) as a function of wavelength for the case is shown graphically. FIG. 10 shows white light on a multilayer thin film according to one or more embodiments shown and described herein, observed at 0 ° and 45 ° relative to a direction perpendicular to the outer surface of the multilayer thin film. The reflectance (%) as a function of wavelength for the case is shown graphically. FIG. 11 shows a multilayer thin film according to one or more embodiments described and described herein, illuminated with white light and viewed at various angles relative to a direction perpendicular to the outer surface of the multilayer thin film. , Lab color space in a graph.

  FIG. 7 generally illustrates one embodiment of a multilayer thin film that can be an omni-directional reflector for reflecting highly saturated red structural colors. The multilayer thin film generally has a reflector layer, at least one absorber layer extending over the reflector layer, and an outer dielectric layer extending over the at least one reflector layer. The at least one absorber layer absorbs light having a wavelength generally less than 550 nm when the dielectric layer has a thickness that provides reflection of light having a wavelength in the red spectrum. The structure and properties of various multilayer thin films having omni-reflective properties to obtain high chroma red structural colors, methods of designing multilayer thin film structures, and applications in which the structures can be used are described in more detail herein. .

  The multilayer thin film structures described herein may be used to omnidirectionally reflect wavelengths in the red spectrum of visible light over a range of incident or viewing angles. The terms "electromagnetic radiation", "electromagnetic radiation" and "light" are used interchangeably herein to refer to light of various wavelengths incident on a multilayer thin film structure, and that such light is It will be appreciated that it may have wavelengths in the ultraviolet (UV), infrared (IR) and visible portions.

1A-1C and FIG. 2 show various types of layers extending across the reflector layer in achieving the desired hue level in the red region of the visible light spectrum when plotted or shown in the Lab color space. Effectiveness has been demonstrated. FIG. 1A shows a ZnS dielectric layer extending over the reflector layer, FIG. 1B shows a Si semiconductor absorber layer extending over the reflector layer, and FIG. 1C shows Fe ₂ O extending over the reflector layer. ₃ shows an O ₃ dielectric absorber layer. Simulations of reflections from each of the multilayer thin films shown in FIGS. 1A-1C were performed as a function of various thicknesses for the dielectric layer, semiconductor absorber layer, and dielectric absorber layer. The simulation results were plotted in the Lab color space, also known as the a ^* b ^* color map, and are shown in FIG. Each data point shown in FIG. 2 represents a dielectric layer for the multilayer thin film shown in FIG. 1A, a semiconductor absorber layer for the multilayer thin film shown in FIG. 1B, or a dielectric layer for the multilayer thin film shown in FIG. 1C. It provides saturation and hue depending on the specific thickness of the body absorber layer.

Hue is sometimes referred to as the angle of a given data point to the positive a ^* axis. The hue value gives the degree of the color indicated by the object, for example, red, green, blue, etc., and the chroma value gives the degree of "brightness" of the color. As shown in FIG. 2, the multilayer thin film shown in FIG. 1A provides a lower chroma than the multilayer thin films shown in FIGS. 1B to 1C. Accordingly, FIGS. 1A-1C and FIG. 2 show that if high chroma colors are desired, an absorber layer, such as a semiconductor layer or a dielectric absorber layer, may be used as a first layer extending over the reflector layer. Has proved to be more favorable.

3A to 3C show the saturation and the hue as a function of the layer thickness. Specifically, FIG. 3A graphically illustrates the saturation and hue as a function of the thickness of the ZnS dielectric layer extending over the Al reflector layer shown in FIG. 1A. FIG. 3B shows the saturation and hue as a function of the thickness of the Si semiconductor absorber layer extending over the Al reflector layer shown in FIG. 1B. FIG. 3C shows the saturation and hue values as a function of the thickness of the Fe ₂ O ₃ dielectric absorber layer extending over the Al reflector layer shown in FIG. 1C. The dotted lines in FIGS. 3A-3C correspond to desired hue values of 10-30 ° in the Lab color space. FIGS. 3A-3C show that higher saturation values in the 10-30 ° hue range are achieved in the case of multilayer thin films where the semiconductor or dielectric absorber layer extends over the reflector layer. Is shown. In embodiments, the outer dielectric layer extends over the absorber layer, for example, a semiconductor absorber layer or a dielectric absorber layer.

  In embodiments, an additional transparent absorber layer extends between the absorber layer and the outer dielectric layer. The location of the transparent absorber layer is selected to enhance the absorption of light at wavelengths below 550 nm but reflect light at wavelengths of about 650 nm.

  In embodiments, FIG. 4 and the following discussion provide a method of calculating the thickness at zero or near-zero electric field at a given wavelength of light. For the purposes of this specification, the term "near zero"

Is defined as FIG. 4 shows a multilayer thin film comprising a substrate layer 2 having a refractive index n _s and a dielectric layer 4 having a total thickness “D”, an incremental thickness “d” and a refractive index “n”. Is shown. The base layer 2 can be a core layer or a reflector layer of a multilayer thin film. 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 θ. The incident light passes through the outer surface 5 and enters the dielectric layer 4 at an angle θ _F with respect to the line 6 and impinges on the surface 3 of the substrate layer 2 at an angle θ _s . For a single dielectric layer, θ _s = θ _F and the energy / electric field (E) can be expressed as E (z) when z = d.

  It is known 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), where it can be shown as follows:

FIG. 5 shows a multi-layer thin film with zero or near zero electric field at the interface between the transparent absorber layer and the outer dielectric layer, indicated by the vertical line slightly to the right of 200 nm on the X-axis. The electric field as a function of the layer thickness for the embodiment is shown by the solid line. The multilayer thin film providing the electric field represented by the solid line in FIG. 5 comprises an Al reflector layer (R) having a thickness of 100 nm and a Fe ₂ O ₃ dielectric absorber having a thickness of 199 nm extending over the Al reflector layer R. Layer (DA), a 14 nm thick Cr transparent absorber layer (TA) extending across the Fe ₂ O ₃ dielectric absorber layer DA, and a 30 nm thick outer ZnS dielectric extending across the transparent absorber layer And a layer (D). The structure of the multilayer thin film that results in the electric field represented by the solid line in FIG. 5 can be described as D / DA / TA / D as shown in the figure. The term "transparent absorber layer" refers to an absorber layer having a thickness such that light passes through the layer. For comparison, the multilayer thin film providing the electric field represented by the dashed line in FIG. 5 has a 100 nm thick Al reflector layer (R) and a 200 nm thick dielectric absorber extending over the Al reflector layer R. It has a body layer DA and an outer ZnS dielectric layer (D) with a thickness of 30 nm extending over the dielectric absorber layer DA (R / DA / D). As shown in FIG. 5, the electric field higher than the electric field existing at the interface between the dielectric absorber layer and the transparent absorber layer in the case of the R / DA / TA / D multilayer thin film is R / DA / T. At the interface between the dielectric absorber layer and the outer dielectric layer in the case of a multilayer thin film. Therefore, in the case of the R / DA / TA / D multilayer thin film, a larger amount of light having a wavelength of 550 nm reaches (not reflected) and is absorbed by the R / DA / TA / D multilayer thin film than in the case of the R / DA / T multilayer thin film. . Also, the electric field at the interface between the outer dielectric layer and air in the case of the R / DA / TA / D multilayer thin film is more than the electric field at the interface between the outer dielectric layer and air in the case of the R / DA / T multilayer thin film. Is lower. Therefore, the light having a wavelength of 550 nm is reflected on the outer surface of the outer dielectric multilayer of the R / DA / TA / D multilayer thin film more than the amount reflected on the outer surface of the outer dielectric layer of the R / DA / T multilayer thin film. The amount is smaller.

FIG. 6 shows the electric field as a function of layer thickness for R / DA / TA / D multilayer thin films exposed to 550 nm wavelength light and 650 nm wavelength light. The multilayer thin film has the same structure and material as the R / DA / TA / D multilayer thin film described above with reference to FIG. 5, that is, an Al reflector layer (R) having a thickness of 100 nm and extending over the Al reflector layer R. A 199 nm thick Fe ₂ O ₃ dielectric absorber layer (DA), a 14 nm thick Cr transparent absorber layer (TA) extending over the Fe ₂ O ₃ dielectric absorber layer DA, and a transparent absorber A 30 nm thick outer ZnS dielectric layer (D) extending across the layers. As shown in FIG. 6, the electric field at the interface between the dielectric absorber layer and the transparent absorber layer, indicated by a vertical line located slightly below 200 nm on the X axis, is: The light with a wavelength of 550 nm (solid line) is much smaller than the light with a wavelength of 650 nm (dotted line). Therefore, the dielectric absorber layer absorbs light having a wavelength of 550 nm much more than light having a wavelength of 650 nm, and reflects light having a wavelength of 650 nm much more than light having a wavelength of 550 nm.

FIG. 7 illustrates a multilayer thin film 10 that reflects an omnidirectional high chroma red structural color according to embodiments disclosed herein. The multilayer thin film 10 includes a reflector layer 110, at least one absorber layer 120 extending over the reflector layer 110, and an outer dielectric layer 130 extending over at least one absorber layer 120. In embodiments, the "outer dielectric layer" has an outer free surface, i.e., an outer surface that is not in contact with the absorber layer or other dielectric layers that are not part of the protective coating. The second at least one absorber layer and the second outer dielectric layer may be a reflector such that the reflector layer 110 is a core layer sandwiched between a pair of absorber layers and a pair of outer dielectric layers. It can be located on the other side of layer 110. Such a multilayer thin film having a core layer sandwiched between a pair of absorber layers and a pair of outer dielectric layers can be referred to as a five-layer multilayer thin film. The reflector layer can have a thickness of 5 to 200 nm and is at least one of "gray metallic" materials, such as Al, Ag, Pt, Sn, for example, Au, Cu, brass, etc. at least one, or those prepared from combinations of the at least one, for example, Fe 2 _{O 3,} chromatic dielectric material such as _TiN of the "chromatic metal (colorful metallic)" material be able to. The at least one absorber layer 120 can have a thickness of 5 to 500 nm and at least one absorber metal material such as, for example, Cr, Cu, Au, brass, etc., and at least one such as Fe ₂ O ₃ , TiN, etc. It can be made of one chromatic dielectric material, for example at least one semiconductor absorber material such as amorphous Si, Ge, or a combination thereof. The outer dielectric layer may have a thickness of less than 2QW of a narrow wavelength center wavelength (eg, 650 nm) of visible light reflected by the multilayer thin film. Outer dielectric layer may be, for example, ZnS, those made from a dielectric material having a refractive index greater than 1.6, such as MgF _2.

FIG. 8 illustrates a multilayer thin film 10 that reflects an omnidirectional high chroma red structural color according to embodiments disclosed herein. The multilayer thin film 10 includes a reflector layer 110, an absorber layer 122 extending over the reflector layer 110, a transparent absorber layer 124 extending over the absorber layer 122, and an outer layer extending over the transparent absorber layer 124. And a dielectric layer 130. The absorber layer 122 can be a metal absorber layer, a dielectric absorber layer, or a semiconductor absorber layer. The second absorber layer and the second transparent absorber so that the reflector layer 110 is a core layer sandwiched between a pair of absorber layers, a pair of transparent absorber layers, and a pair of outer dielectric layers. It can be seen that the layer and the second outer dielectric layer can be located on the other side of the reflector layer 110. Such a multilayer thin film comprising a pair of absorber layers, a pair of transparent absorber layers and a core layer sandwiched between a pair of outer dielectric layers can be referred to as a seven-layer multilayer thin film. The reflector layer may have a thickness of 5 to 200 nm and may be at least one of "grey metal" materials, for example Al, Ag, Pt, Sn, etc., e.g. at least one of metal "material can be, for example Fe 2 _{O 3,} at least one of chromatic dielectric material, such as _TiN, or those made from these combinations. The absorber layer 120 may have a thickness of 5 to 500 nm, and may include at least one absorber metal material such as Cr, Cu, Au, and brass, for example, a dielectric absorber such as Fe ₂ O ₃ and TiN. It can be made from a material, for example at least one semiconductor absorber material such as amorphous Si, Ge, or a combination thereof. Transparent absorber layer may have a thickness of 5 to 20 nm, for example Cr, Ge, Ni, stainless steel, Ti, Si, V, TiN , W, Mo, at least one of Nb and _Fe 2 _{O 3} It can be produced from one species. The outer dielectric layer may have a thickness of less than 2QW of a narrow wavelength center wavelength (eg, 650 nm) of visible light reflected by the multilayer thin film, and the outer dielectric layer may include, for example, ZnS, MgF _2, etc. It can be manufactured from a dielectric material having a refractive index greater than 0.6.

FIG. 9 illustrates the reflections provided by one or more embodiments disclosed herein when white light falls at angles of 0 ° and 45 ° with respect to a direction perpendicular to the outer surface of the multilayer thin film. Representative reflectance spectra are shown in the form of reflectance (%) for the light wavelength. As shown by the reflectivity spectrum, for a wavelength of 550 nm, the 0 ° and 45 ° curves both show very low reflectivity, eg, less than 10%. However, a sharp increase in reflectivity at wavelengths of 560-570 nm was observed to reach a maximum of about 90% at 700 nm. The portion or region of the graph on the right hand side (IR side) of the curve represents the IR region of the reflection band provided by the embodiment. The sharp increase in reflectivity can be attributed to a 0 ° curve (S _UV (0) extending from a low reflectivity portion at a wavelength less than 550 nm to a high reflectivity portion, for example, greater than 70%, preferably greater than 80%, more preferably greater than 90%. °)) and the UV end of the 45 ° curve (S _UV (45 °)). A measure of the degree of omnidirectionality provided by embodiments may be a shift between the S _UV (0 °) and S _UV (45 °) ends in the visible FWHM position. A zero shift between the S _UV (0 °) and S _UV (45 °) edges, ie, no shift, characterizes a completely omnidirectional multilayer film. The shift between the S _UV (0 °) edge and the S _UV (45 °) edge for the embodiments disclosed herein is less than 100 nm, preferably less than 75 nm, more preferably less than 50 nm, even more preferably less than 25 nm. In some cases, when viewed from a human viewpoint at an angle of 0 to 45 °, the human eye does not change the color of the surface of the multilayer thin film, but as if the multilayer thin film is omnidirectional. Can be seen. The linear portion 200 at the UV side end is inclined at an angle (β) of more than 60 ° with respect to the X axis, has a length L of about 40 on the axis of reflectivity, and has a slope of 1.4. . In embodiments, the linear portion is inclined at an angle greater than 70 ° with respect to the x-axis. In other embodiments, the straight portion is inclined at an angle greater than 75 °. The reflection band has a visible FWHM of less than 300 nm, preferably less than 200 nm, more preferably less than 150 nm, even more preferably less than 100 nm. The center wavelength λ _C of the visible reflection band shown in FIG. 9 is defined as a wavelength that is equidistant from the UV side end of the reflection band and the IR end of the IR spectrum in the visible FWHM. The term "visible FWHM" means the width of the reflection band between the UV end of this curve and the end of the IR spectral range beyond which reflections provided by the omni-directional reflector become invisible to the human eye. I do. The embodiments disclosed herein use the non-visible IR portion of the electromagnetic radiation spectrum to provide sharp or structural colors, i.e., the embodiments disclosed herein provide a narrow band of reflected visible light. While utilizing the non-visible IR portion of electromagnetic radiation, it should be understood that a fairly broad band of electromagnetic radiation may extend into the IR region.

Referring now to FIG. 10, the reflection spectrum of the multilayer thin film according to the embodiments disclosed herein shows a narrow visible light band with a peak in the visible spectrum. This peak is the wavelength of the maximum reflectance, and when observed perpendicularly to the outer surface of the multilayer thin film (λ _C (0 °)), the center wavelength of the reflectance curve indicated by the multilayer thin film and the peak at the outer surface of the multilayer thin film On the other hand, the center wavelength λ _C (45 °) of the reflectance curve shown by the multilayer thin film when observed at an angle of 45 ° can be defined. When the outer surface of the multilayer thin film is observed from an angle of 45 ° as compared with a case where the surface is observed from an angle of 0 ° (λ _C (0 °)), that is, a case where the surface is observed perpendicularly to the surface, for example, The shift or displacement of its λ _C (λ _C (45 °)) when the outer surface is tilted 45 ° with respect to the human eye looking at that surface is shown in FIG. The shift of λ _C (Δλ _C ) is a measure of the omni-directionality of the omni-directional reflector. Zero shift of λ _C , ie

Represents reflection from a completely omnidirectional multilayer thin film. However, the disclosed embodiments result in a [Delta] [lambda] _C of less than 100 nm, preferably less than 75 nm, more preferably less than 50 nm, and even more preferably less than 25 nm, when viewed from a human perspective at an angle of 0-45 [deg.]. In addition, to the human eye, the surface of the reflector does not change color, but it can appear as if the multilayer film is omnidirectional. The shift of Δλ _C can be determined by a reflectance versus wavelength plot determined from the multilayer film exposed to white light, or by modeling the multilayer film. The narrow band of reflected visible light shown in FIG. 10 results in a red color, and a small shift or displacement of the center wavelength when viewing the multilayer thin film at an angle of 0-45 ° has an omnidirectional red structure. It can be seen that the multi-layered thin film reflects color, that is, bright red, which does not appear to change color to the human eye when viewed at an angle of 0-45 °.

Both the 0 ° and 45 ° curves in FIG. 10 show very low reflectivity, eg, less than 10%, for wavelengths less than 550 nm. However, a sharp increase in reflectivity at wavelengths of 560-570 nm, which reaches a maximum of about 90% at 700 nm, is observed. It can be seen that the portion of the graph to the right (IR side) of the curve represents the IR portion of the reflection band provided by the embodiments. This sharp increase in reflectivity can be attributed to low to high reflectivity portions below 550 nm, such as high reflectivity portions above 70%, preferably above 80%, more preferably above 90%. It is characterized by the 0 ° curve (S _UV (0 °)) extending to the UV side edge of the 45 ° curve (S _UV (45 °)). The reflection band has a visible FWHM of less than 300 nm, preferably less than 200 nm, more preferably less than 150 nm, even more preferably less than 100 nm. The narrow band of reflected visible light shown in FIG. 10 results in a red color, and a small shift or displacement of the center wavelength when viewing the multilayer thin film at an angle of 0-45 ° has an omnidirectional red structure. It can be seen that the multi-layered thin film reflects color, that is, bright red, which does not appear to change color to the human eye when viewed at an angle of 0-45 °.

Referring to FIG. 11, the reflection characteristics of the multilayer thin film according to the embodiment disclosed in the present specification may be described in a Lab color space. Lab color space has an X-coordinate and ^{b *} of the Y-coordinate of ^{a *.} Figure 11 shows the reflection characteristic of the conventional paint when observed at an angle of 0 to 45 °, the hue shift is shown as [Delta] [theta] _2. By comparison, multilayer thin films according to embodiments disclosed herein result in a small hue shift (Δθ ₁ ) when observed at 0-45 °. The hue shift represented by Δθ _{1 in} FIG. 11 is less than 30 °, preferably less than 25 °, more preferably less than 20 °, and even more preferably less than 15 °. FIG. 11 also shows that the multilayer thin film according to the embodiments disclosed herein provides a hue corresponding to red, that is, a hue between θ _{1L and} θ _1H . In embodiments, the multilayer thin film provides a hue of 0-30 ° in the Lab color space, preferably 5-25 ° in the Lab color space, more preferably 10-22 ° in the Lab color space. In embodiments, a multilayer thin film according to embodiments disclosed herein has an observed color exhibited by the multilayer thin film structure when viewed at 0 and 45 °, wherein the observed color is represented by θ _1L to θ _1H. Has a hue shift within. The chroma for multilayer thin films according to embodiments disclosed herein is significantly higher than conventional paints. In embodiments, the saturation for the multilayer thin film can range from 60 to 120, preferably 80 to 110, more preferably 85 to 105.

  Multilayer films according to embodiments disclosed herein can be used as pigments, for example, paint pigments for paints used to paint objects, or as continuous films applied to objects. When used as a pigment, paint binders, fillers, and the like can be used and mixed with the pigment to provide a paint that exhibits a high chroma red structure color in all directions. The terms "substantially" and "about" may be used herein to denote the inherent degree of uncertainty that can be attributed to any quantitative comparison, value, measurement, or other expression. Note that These terms are also used to describe the degree to which quantitative expressions can vary from the stated reference without changing the basic function of the subject matter in question.

  While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Furthermore, while various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications as fall within the scope of the claimed subject matter.

Claims (20)

Omnidirectional high chroma red structural color including a multilayer thin film having a reflector layer, at least one absorber layer extending over the reflector layer, and an outer dielectric layer extending over the at least one absorber layer. A multilayer interference thin film that reflects
The multilayer thin film reflects a single narrow band of visible light when exposed to white light, and the outer dielectric layer has a thickness of 2.0 QW or less of the central wavelength of the single narrow band of visible light. Having
Said single narrow band of visible light,
Visible FWHM width less than 200 nm;
A color of 0 ° to 30 ° in a Lab color space; and less than 30 ° in a Lab color space when the multilayer thin film is observed at an angle of 0 to 45 ° with respect to a direction perpendicular to the outer surface of the outer dielectric layer. Hue shift of
A multilayer interference thin film that reflects omnidirectional high-saturation red structural color.   The multilayer interference thin film according to claim 1, wherein the reflector layer has a thickness of 5 to 200 nm and is made of at least one of Al, Ag, Pt, and Sn.   The multilayer interference thin film according to claim 1, wherein the at least one absorber layer is at least one dielectric absorber layer extending between the reflector layer and the outer dielectric layer.   The multilayer interference thin film according to claim 3, wherein the at least one dielectric absorber layer is made of at least one of an oxide and a nitride. Wherein at least one dielectric absorber layer, which has been made from at least one of _Fe 2 _{O 3} and TiN, having a thickness of 5 to 500 nm, the multilayer interference thin film according to claim 1.   The multilayer interference thin film of claim 1, wherein the outer dielectric layer has a refractive index greater than 1.6. Wherein are those external dielectric layer is made of at least one of _MgF 2, ZnS and TiO _2, the multilayer interference thin film according to claim 6.   The multilayer interference thin film according to claim 7, wherein a central wavelength of a single narrow band of reflected visible light is 600 to 700 nm, and a thickness of the outer dielectric layer is less than 175 nm.   The multilayer interference thin film according to claim 1, wherein the at least one absorber layer is a dielectric absorber layer and a transparent absorber layer.   The multilayer interference thin film according to claim 9, wherein the transparent absorber layer extends over the dielectric absorber layer and is disposed between the dielectric absorber layer and the outer dielectric layer. It said dielectric absorber layer are those made from at least one of Fe ₂ O ₃ and TiN, multilayer interference thin film according to claim 9.   The multilayer interference thin film according to claim 1, wherein the dielectric absorber layer has a thickness of 5 to 500 nm. Those wherein the transparent absorber layer made Cr, Ge, Ni, stainless steel, Ti, Si, V, TiN , W, Mo, at least one of Nb and _Fe 2 _{O 3,} claim 9 2. The multilayer interference thin film according to item 1.   14. The multilayer interference thin film according to claim 13, wherein the transparent absorber layer has a thickness of 5 to 20 nm.   The single narrow band of visible light has a visible FWHM width of less than 200 nm, a color between 5 ° and 25 ° in the Lab color space, and 0-45 ° relative to a direction perpendicular to the outer surface of the outer dielectric layer. The multilayer interference thin film according to claim 1, wherein the multilayer interference thin film has a hue shift of less than 20 ° in a Lab space color map when the multilayer thin film is observed at an angle of?   The single narrow band of visible light has a visible FWHM width of less than 200 nm, a color between 10 ° and 25 ° in the Lab color space, and 0-45 ° relative to a direction perpendicular to the outer surface of the outer dielectric layer. 2. The multilayer interference thin film according to claim 1, wherein the multilayer interference thin film has a hue shift of less than 15 ° in a Lab space color map when the multilayer thin film is observed at an angle. A reflector layer, a dielectric absorber layer extending over the reflector layer, an outer dielectric layer extending over the dielectric absorber layer, and between the dielectric absorber layer and the outer dielectric layer An omnidirectional high chroma red structure color multilayer thin film including a multilayer thin film having a transparent absorber layer extending to
The multilayer thin film reflects a single narrow band of visible light when exposed to white light, and the outer dielectric layer has a thickness of 2.0 QW or less of the central wavelength of the single narrow band of visible light. The single narrow band of visible light has
Visible FWHM width less than 200 nm;
A color of 0 ° to 30 ° in a Lab color space; and less than 30 ° in a Lab color space when the multilayer thin film is observed at an angle of 0 to 45 ° with respect to a direction perpendicular to the outer surface of the outer dielectric layer. Hue shift of
Omnidirectional high-saturation red structure color multilayer thin film having   The omnidirectional high chroma red structural color multilayer thin film of claim 17, wherein the dielectric absorber layer is made of at least one of an oxide and a nitride and has a thickness of 5 to 500 nm. Said dielectric absorber layer are those made from at least one of Fe ₂ O ₃ and TiN, omnidirectional high chroma red structural color multilayer thin film of claim 18. The transparent absorber layer, Cr, has been made Ge, Ni, stainless steel, Ti, Si, V, TiN , W, Mo, at least one of Nb and _Fe 2 _{O 3, 5~} The omnidirectional high chroma red structural color multilayer thin film of claim 17 having a thickness of 20 nm.

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