Non-color shifting multilayer structures

Information

  • Patent Grant
  • 10788608
  • Patent Number
    10,788,608
  • Date Filed
    Tuesday, April 1, 2014
    9 years ago
  • Date Issued
    Tuesday, September 29, 2020
    3 years ago
Abstract
An omnidirectional multilayer thin film is provided. The multilayer thin film includes a multilayer stack having a first layer of a first material and a second layer of a second material, the second layer extending across the first layer. The multilayer stack reflects a narrow band of electromagnetic radiation having a full width at half maximum (FWHM) of less than 300 nanometers (nm) and a color/hue shift of less than 30 degrees when the multilayer stack is exposed to broadband electromagnetic radiation and viewed from angles between 0 and 45 degrees. In some instances, the multilayer stack has a total thickness of less than 2 microns (μm). Preferably, the multilayer thin film has a total thickness of less than 1.5 μm and more preferably less than 1.0 μm.
Description
FIELD OF THE INVENTION

The present invention is related to multilayer thin film structures, and in particular to multilayer thin film structures that exhibit a minimum or non-noticeable color shift when exposed to broadband electromagnetic radiation and viewed from different angles.


BACKGROUND OF THE INVENTION

Pigments made from multilayer structures are known. In addition, pigments that exhibit or provide a high-chroma omnidirectional structural color are also known. However, such prior art pigments have required as many as 39 thin film layers in order to obtain desired color properties.


It is appreciated that cost associated with the production of thin film multilayer pigments is proportional to the number of layers required. As such, the cost associated with the production of high-chroma omnidirectional structural colors using multilayer stacks of dielectric materials can be prohibitive. Therefore, a high-chroma omnidirectional structural color that requires a minimum number of thin film layers would be desirable.


SUMMARY OF THE INVENTION

An omnidirectional multilayer thin film is provided. The multilayer thin film includes a multilayer stack having a first layer of a first material and a second layer of a second material, the second layer extending across the first layer. The multilayer stack reflects a narrow band of electromagnetic radiation having a full width at half maximum (FWHM) of less than 300 nanometers (nm) and in some instances has a FWHM of less than 200 nm. The multilayer stack also has a color shift in the form of a center wavelength shift of less than 50 nm, preferably less than 40 nm and more preferably less than 30 nm, when the multilayer stack is exposed to broadband electromagnetic radiation and viewed from angles between 0 and 45 degrees. In the alternative, the color shift can be in the form of a hue shift of less than 30°, preferably less than 25° and more preferably less than 20°. In addition, the multilayer stack may or may not reflect a band of electromagnetic radiation in the ultraviolet (UV) range and/or reflect a band of electromagnetic radiation in the infrared (IR) range.


In some instances, the multilayer stack has a total thickness of less than 2 microns (μm). Preferably, the multilayer thin film has a total thickness of less than 1.5 μm and more preferably less than 1.0 μm.


The multilayer stack can be made from dielectric layers, i.e. the first layer and the second layer can be made from dielectric materials. In the alternative, the first layer can be a dielectric material and the second layer can be an absorbing material. The first layer has a thickness between 30-300 nm. The absorbing material can be a selective absorbing material, or in the alternative, a non-selective absorbing material. The selective absorbing material absorbs only a desired portion of the visible electromagnetic radiation spectrum and can be made from materials such as copper (Cu), gold (Au), zinc (Zn), tin (Sn), alloys thereof, and the like. In the alternative, the selective absorbing material can be made from a colorful dielectric material such as Fe2O3, Cu2O, and combinations thereof. Such a second layer made from a selective absorbing material can have a thickness between 20-80 nm.


The non-selective absorbing material/layer generally absorbs all of the visible electromagnetic radiation spectrum and can be made from materials such as chromium (Cr), tantalum (Ta), tungsten (W), molybdenum (Mo), titanium (Ti), titanium nitride, niobium (Nb), cobalt (Co), silicon (Si), germanium (Ge), nickel (Ni), palladium (Pd), vanadium (V), ferric oxide, and combinations or alloys thereof. Such a non-selective absorbing layer has a thickness between 5-20 nm.


The multilayer stack can further include a reflector layer with the first and second layers extending across the reflector layer. The reflector layer can be made from a metal such as aluminum (Al), silver (Ag), Au, platinum (Pt), Cr, Cu, Zn, Sn, and alloys thereof. Also, the reflector has a thickness between 50-200 nm.


The reflected narrow band of electromagnetic radiation characteristic of the multilayer thin film can have a generally symmetrical peak. In the alternative, the reflected narrow band of electromagnetic radiation does not have a symmetrical peak. In some instances, the multilayer thin film provides a narrow band of reflected electromagnetic radiation in the visible range by taking advantage of the non-visible UV range and/or IR range. Stated differently, the multilayer thin film can reflect a generally broad band of electromagnetic radiation; however, only a narrow band is visible. In addition, the narrow band of visible electromagnetic radiation has a very low color shift, e.g. a center wavelength shift of less than 50 nm, when the multilayer thin film is viewed from angles between 0 and 45 degrees.


The multilayer thin film can also have a low hue shift when viewed from 0 and 45 degrees. For example, the multilayer thin film can have a hue shift of less than 30 degrees when the thin film is viewed between angles of 0 and 45 degrees. In the alternative, the multilayer thin film can have a hue shift of less than 25 degrees, preferably less than 20 degrees, when the thin film is viewed between angles of 0 and 45 degrees.





BRIEF DESCRIPTION OF THE FIGURES


FIG. 1A is a schematic illustration of a dielectric layer (DL) reflecting and transmitting incident electromagnetic radiation;



FIG. 1B is a schematic illustration of a reflector layer (RL) reflecting incident electromagnetic radiation;



FIG. 1C is a schematic illustration of an absorbing layer (AL) absorbing incident electromagnetic radiation;



FIG. 1D is a schematic illustration of a selective absorbing layer (SAL) reflecting, absorbing and transmitting incident electromagnetic radiation;



FIG. 2 is a schematic illustration of reflectance and transmission of incident electromagnetic radiation by a 1st generation omnidirectional structural color multilayer thin film made from a plurality of dielectric layers;



FIG. 3 is a schematic illustration of a 1st generation omnidirectional structural color multilayer thin film made from a plurality of dielectric layers;



FIG. 4 is a graphical representation showing a comparison of the range to mid-range ratio of 0.2% for the transverse magnetic mode and transverse electric mode of electromagnetic radiation;



FIG. 5 is a graphical representation of reflectance as a function of wavelength for Case III shown in FIG. 4;



FIG. 6 is a graphical representation of the dispersion of the center wavelength in Case I, II and III shown in FIG. 4;



FIG. 7 is a schematic illustration of reflectance and absorption of incident electromagnetic radiation by a 2nd generation omnidirectional structural color multilayer thin film made from a plurality of dielectric layers and an absorbing layer;



FIG. 8 is a schematic illustration of a 2nd generation omnidirectional structural color multilayer thin film made from a plurality of dielectric layers and an absorbing layer and/or reflecting layer;



FIG. 9A is schematic illustration of a 2nd generation 5-layer omnidirectional structural color multilayer thin film made from a plurality of dielectric layers and an absorbing/reflecting layer having a chroma (C*) of 100 and a reflectance (Max R) of 60%;



FIG. 9B is a graphical representation of reflectance versus wavelength for the 2nd generation 5-layer multilayer stack thin film shown in FIG. 9A compared to a 1st generation 13-layer multilayer thin film and for viewing angles of 0 and 45 degrees;



FIG. 10 is a schematic illustration of a 3rd generation omnidirectional structural color multilayer thin film made from a dielectric layer, a selective absorbing layer (SAL) and a reflector layer;



FIG. 11A is a schematic illustration of a zero or near-zero electric field point within a ZnS dielectric layer exposed to electromagnetic radiation (EMR) having a wavelength of 500 nm;



FIG. 11B is a graphical illustration of the absolute value of electric field squared (|E|2) versus thickness of the ZnS dielectric layer shown in Figure lA when exposed to EMR having wavelengths of 300, 400, 500, 600 and 700 nm;



FIG. 12 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 normal direction to the outer surface of the dielectric layer;



FIG. 13 is a schematic illustration of a ZnS dielectric layer with a Cr absorber layer located at the zero or near-zero electric field point within the ZnS dielectric layer for incident EMR having a wavelength of 434 nm;



FIG. 14 is a graphical representation of percent reflectance versus reflected EMR wavelength for a multilayer stack without a Cr absorber layer (e.g., FIG. 1A) and a multilayer stack with a Cr absorber layer (e.g., FIG. 3A) exposed to white light;



FIG. 15A is a graphical illustration of first harmonics and second harmonics exhibited by a ZnS dielectric layer extending over an Al reflector layer (e.g., FIG. 4A);



FIG. 15B is a graphical illustration of percent reflectance versus reflected EMR wavelength for a multilayer stack with a ZnS dielectric layer extending across an Al reflector layer, plus a Cr absorber layer located within the ZnS dielectric layer such that the second harmonics shown in FIG. 8A are absorbed;



FIG. 15C is a graphical illustration of percent reflectance versus reflected EMR wavelength for a multilayer stack with a ZnS dielectric layer extending across an Al reflector layer, plus a Cr absorber layer located within the ZnS dielectric layer such that the first harmonics shown in FIG. 8A are absorbed;



FIG. 16A is a graphical illustration of electric field squared versus dielectric layer thickness showing the electric field angular dependence of a Cr absorber layer for exposure to incident light at 0 and 45 degrees;



FIG. 16B is a graphical illustration of percent absorbance by a Cr absorber layer versus reflected EMR wavelength when exposed to white light at 0 and 45° angles relative to normal of the outer surface (0° being normal to surface);



FIG. 17A is a schematic illustration of a red omnidirectional structural color multilayer stack according to an embodiment of the present invention;



FIG. 17B is a graphical illustration of percent absorbance of the Cu absorber layer shown in FIG. 10A versus reflected EMR wavelength for white light exposure to the multilayer stack shown in FIG. 10A at incident angles of 0 and 45°;



FIG. 18 is a graphical comparison between calculation/simulation data and experimental data for percent reflectance versus reflected EMR wavelength for a proof of concept red omnidirectional structural color multilayer stack exposed to white light at an incident angle of 0°;



FIG. 19 is a graphical illustration of percent reflectance versus wave length for an omnidirectional structural color multilayer stack according to an embodiment of the present invention;



FIG. 20 is a graphical illustration of percent reflectance versus wave length for an omnidirectional structural color multilayer stack according to an embodiment of the present invention;



FIG. 21 is a graphical illustration of percent reflectance versus wave length for an omnidirectional structural color multilayer stack according to an embodiment of the present invention;



FIG. 22 is a graphical illustration of percent reflectance versus wave length for an omnidirectional structural color multilayer stack according to an embodiment of the present invention;



FIG. 23 is a graphical representation of a portion of an a*b* color map using the CIELAB color space in which the chroma and hue shift are compared between a conventional paint and a paint made from pigments according to an embodiment of the present invention (Sample (b));



FIG. 24 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention;



FIG. 25 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention; and



FIG. 26 is a schematic illustration of an omnidirectional structural color multilayer stack according to an embodiment of the present invention.





DETAILED DESCRIPTION OF THE INVENTION

An omnidirectional structural color is provided. The omnidirectional structural color has the form of a multilayer thin film (also referred to as a multilayer stack herein) that reflects a narrow band of electromagnetic radiation in the visible spectrum and has a small or non-noticeable color shift when the multilayer thin film is viewed from angles between 0 to 45 degrees. The multilayer thin film can be used as pigment in a paint composition, a continuous thin film on a structure and the like.


The multilayer thin film includes a multilayer stack that has a first layer and a second layer extending across the first layer. In some instances, the multilayer stack reflects a narrow band of electromagnetic radiation that has a FWHM of less than 300 nm, preferably less than 200 nm and in some instances less than 150 nm. The multilayer thin film also has a color shift of less than 50 nm, preferably less than 40 nm and more preferably less than 30 nm, when the multilayer stack is exposed to broadband electromagnetic radiation, e.g. white light, and viewed from angles between 0 and 45 degrees. Also, the multilayer stack may or may not have a separate reflected band of electromagnetic radiation in the UV range and/or the IR range.


The overall thickness of the multilayer stack is less than 2 μm, preferably less than 1.5 μm, and still more preferably less than 1.0 μm. As such, the multilayer stack can be used as paint pigment in thin film paint coatings.


The first and second layers can be made from dielectric material, or in the alternative, the first and/or second layer can be made from an absorbing material. Absorbing materials include selective absorbing materials such as Cu, Au, Zn, Sn, alloys thereof, and the like, or in the alternative colorful dielectric materials such as Fe2O3, Cu2O, combinations thereof, and the like. The absorbing material can also be a non-selective absorbing material such as Cr, Ta, W, Mo, Ti, Ti-nitride, Nb, Co, Si, Ge, Ni, Pd, V, ferric oxides, combinations or alloys thereof, and the like. The thickness of an absorbing layer made from selective absorbing material is between 20-80 nm whereas the thickness of an absorbing layer made from non-selective absorbing material is between 5-30 nm.


The multilayer stack can also include a reflector layer which the first layer and the second layer extend across, the reflector layer made from metals such as Al, Ag, Pt, Cr, Cu, Zn, Au, Sn, alloys thereof, and the like. The reflector layer typically has a thickness between 30-200 nm.


The multilayer stack can have a reflected narrow band of electromagnetic radiation that has the form of a symmetrical peak within the visible spectrum. In the alternative, the reflected narrow band of electromagnetic radiation in the visible spectrum can be adjacent to the UV range such that a portion of the reflected band of electromagnetic radiation, i.e. the UV portion, is not visible to the human eye. In the alternative, the reflected band of electromagnetic radiation can have a portion in the IR range such that the IR portion is likewise not visible to the human eye.


Whether the reflected band of electromagnetic radiation that is in the visible spectrum borders the UV range, the IR range, or has a symmetrical peak within the visible spectrum, multilayer thin films disclosed herein have a reflected narrow band of electromagnetic radiation in the visible spectrum that has a low, small or non-noticeable color shift. The low or non-noticeable color shift can be in the form of a small shift of a center wavelength for a reflected narrow band of electromagnetic radiation. In the alternative, the low or non-noticeable color shift can be in the form of a small shift of a UV-sided edge or IR-sided edge of a reflected band of electromagnetic radiation that borders the IR range or UV range, respectively. Such a small shift of a center wavelength, UV-sided edge and/or IR-sided edge is typically less than 50 nm, in some instances less than 40 nm, and in other instances less than 30 nm when the multilayer thin film is viewed from angles between 0 and 45 degrees.


Turning now to FIG. 1, FIGS. 1A-1D illustrate the basic components of an omnidirectional structural color design. In particular, FIG. 1A illustrates a dielectric layer exposed to incident electromagnetic radiation. In addition, the dielectric layer (DL) reflects a portion of the incident electromagnetic radiation and transmits a portion thereof. In addition, the incident electromagnetic radiation is equal to the transmitted portion and the reflected portion and typically the transmitted portion is much greater than the reflected portion. Dielectric layers are made from dielectric materials such as SiO2, TiO2, ZnS, MgF2, and the like.


In sharp contrast, FIG. 1B illustrates a reflective layer (RL) in which all of the incident electromagnetic radiation is reflected and essentially has zero transmittance. Reflector layers are typically made from materials such as aluminum, gold, and the like.



FIG. 1C illustrates an absorbing layer (AL) in which incident electromagnetic radiation is absorbed by the layer and not reflected or transmitted. Such an absorbing layer can be made from, for example, graphite. Also, the total incident electromagnetic radiation is absorbed and transmission and reflectance is approximately zero.



FIG. 1D illustrates a partial or selective absorbing layer (SAL) in which a portion of the incident electromagnetic radiation is absorbed by the layer, a portion is transmitted, and a portion is reflected. As such, the amount of electromagnetic radiation transmitted, absorbed, and reflected equals the amount of incident electromagnetic radiation. In addition, such selective absorbing layers can be made from material such as a thin layer of chromium, layers of copper, brass, bronze, and the like.


With respect to the present invention, three generations of design and manufacture of omnidirectional structural color thin films are disclosed.


First Generation

Referring now to FIG. 2, a schematic illustration of a multilayer thin film having a plurality of dielectric layers is shown. In addition, the reflectance and transmittance of an incident electromagnetic radiation is schematically shown. As stated above, typically transmission of the incident electromagnetic radiation is much greater than reflectance thereof and thus many layers are required.



FIG. 3 shows part of a multilayer thin film made from dielectric layers having a first index of refraction (DL1) and a second index of refraction (DL2). It should be appreciated that the double lines between the layers simply represent an interface between the different layers.


Not being bound by theory, one method or approach for designing and manufacturing a desired multilayer stack is the following.


When electromagnetic radiation impacts a material surface, waves of the radiation can be reflected from or transmitted through the material. Furthermore, when electromagnetic radiation impacts the first end 12 of the multilayer structure 10 at the angle θ0, the reflected angles the electromagnetic waves make with the surface of the high and low refractive index layers are θH and θL, respectively. Using Snell's law:

n0 Sin θ0=nL Sin θL=nH Sin θH   (1)

the angles θH and θL can be determined if the refractive indices nH and nL are known.


Regarding omnidirectional reflectivity, a necessary but not sufficient condition for the TE mode and the TM mode of electromagnetic radiation requires the maximum angle of refraction (θH,MAX) inside the first layer to be less than the Brewster angle (θB) of the interface between the first layer and the second layer. If this condition is not satisfied, the TM mode of the electromagnetic waves will not be reflected at the second and all subsequent interfaces and thus will transmit through the structure. Using this consideration:











Sin






θ

H
,
Max



=


n
0


n
H








and




(
2
)







Tan






θ
B


=


n
L


n
H






(
3
)








Thereby requiring:










n
0

<



n
H



n
L





n
H
2

+

n
L
2








(
4
)







In addition to the necessary condition represented by Equation 4, if electromagnetic radiation of wavelength λ falls on a multilayer structure with an angle θ0, and the individual bi-layers of the multilayer structure have thicknesses dH and dL with respective refractive indices nH and nL, the characteristic translation matrix (FT) can be expressed as:










F
T

=


1

1
+

ρ
T










e

i






δ
L







ρ
T



e


-
i







δ
L










ρ
T



e

i






δ
L







e


-
i







δ
L








×

1

1
-

ρ
T










e

i






δ
H







ρ
T



e


-
i







δ
H










ρ
T



e

i






δ
H







e


-
i







δ
H













(
5
)








which can also be expressed as:










F
T

=


1

1
+

ρ
T
2











e

i


(


δ
L

+

δ
H


)



-


ρ
T
2



e

-

i


(


δ
H

-

δ
L


)










-
2


i






ρ
T



e


-
i







δ
H




Sin






δ
L







2

i






ρ
T



e

i






δ
H




Sin






δ
L






e

-

i


(


δ
L

+

δ
H


)




-


ρ
T
2



e

-

i


(


δ
H

-

δ
L


)
















(
6
)








and where:










δ
H

=



2





π

λ



n
H



d
H


Cos






θ
H






(
7
)







δ
L

=



2





π

λ



n
L



d
L


Cos






θ
L






(
8
)








Cos






θ
H


=


1
-



n
o
2



Sin
2



θ
0



n
H
2










and




(
9
)







Cos






θ
L


=


1
-



n
o
2



Sin
2



θ
0



n
L
2








(
10
)








In addition,











ρ
T

=



n
HT

-

n
LT




n
HT

+

n
LT









where




(
11
)







n
HT

=

{






n
H


Cos






θ
H









n
H


Cos






θ
H











(

for





TM





and





TE





polarization





respectively

)






and






(
12
)







n
LT

=

{






n
L


Cos






θ
L









n
L


Cos






θ
L











(

for





TM





and





TE





polarization





respectively

)







(
13
)








Solving ρT explicitly for TE and TM:











ρ
TM

=




n
H


Cos






θ
L


-


n
L


Cos






θ
H






n
H


Cos






θ
L


+


n
L


Cos






θ
H










and




(
14
)







ρ
TE

=




n
H


Cos






θ
H


-


n
L


Cos






θ
L






n
H


Cos






θ
H


+


n
L


Cos






θ
L








(
15
)







A viewing angle dependant band structure can be obtained from a boundary condition for the edge, also known as the bandedge, of the total reflection zone. For the purposes of the present invention, bandedge is defined as the equation for the line that separates the total reflection zone from the transmission zone for the given band structure.


A boundary condition that determines the bandedge frequencies of the high reflectance band can be given by:

Trace |FT|=−1   (16)

Thus, from equation 3:












Cos


(


δ
H

+

δ
H


)


-


ρ
T
2



Cos


(


δ
H

-

δ
L


)





1
-

ρ
T
2



=

-
1





(
17
)








or expressed differently:











Cos
2



(



δ
H

+

δ
L


2

)


=


ρ
T
2




Cos
2



(



δ
H

-

δ
L


2

)







(
18
)








Combining equations 15 and 7, the following bandedge equation is obtained:










Cos


(


π






L
+


λ

)


=


±



ρ
T






Cos


(


π






L
-


λ

)







(
19
)








Where:











L
+

=



n
H



d
H


Cos






θ
H


+


n
L



d
L


Cos






θ
L










and


:






(
20
)







L
-

=



n
H



d
H


Cos






θ
H


+


n
L



d
L


Cos






θ
L







(
21
)








The + sign in the bandedge equation shown above represents the bandedge for the long wavelength (λlong) and the − sign represents the bandedge for the short wavelength (λshort). Recompiling equations 20 and 21:











Cos


(


π






L
+



λ
long


)


=


+



ρ
TE






Cos


(


π






L
-



λ
long


)







and









Cos


(


π






L
+



λ
Short


)


=


-



ρ
TE






Cos


(


π






L
-



λ
Short


)








(
22
)








for the TE mode, and:











Cos


(


π






L
+



λ
long


)


=


+



ρ
TM






Cos


(


π






L
-



λ
long


)







and









Cos


(


π






L
+



λ
Short


)


=


-



ρ
TM






Cos


(


π






L
-



λ
Short


)








(
23
)








for the TM mode.


An approximate solution of the bandedge can be determined by the following expression:

L=nHdH Cos θH−nLdL Cos θL˜0   (24)

This approximate solution is reasonable when considering a quarter wave design (described in greater detail below) and optical thicknesses of the alternating layers chosen to be equal to each other. In addition, relatively small differences in optical thicknesses of the alternating layers provide a cosine close to unity. Thus, equations 23 and 24 yield approximate bandedge equations:












λ
long



(

θ
0

)


=



π







L
+



(

θ
0

)





Cos

-
1







ρ
TE



(

θ
0

)











and










λ
Short



(

θ
0

)


=


π







L
+



(

θ
0

)





Cos

-
1




(

-




ρ
TE



(

θ
0

)





)








(
25
)








for the TE mode and:












λ
long



(

θ
0

)


=


π







L
+



(

θ
0

)





Cos

-
1







ρ
TM



(

θ
0

)












and








λ
Short



(

θ
0

)


=


π







L
+



(

θ
0

)





Cos

-
1




(

-




ρ
TM



(

θ
0

)





)








(
26
)








for the TM mode.


Values for L+ and ρTM as a function of incident angle can be obtained from equations 7, 8, 14, 15, 20 and 21, thereby allowing calculations for λlong and λshort in the TE and TM modes as a function of incident angle.


The center wavelength of an omnidirectional reflector (λc), can be determined from the relation:

λc=2(nHdH Cos θH+nLdL Cos θL)   30)

The center wavelength can be an important parameter since its value indicates the approximate range of electromagnetic wavelength and/or color spectrum to be reflected. Another important parameter that can provide an indication as to the width of a reflection band is defined as the ratio of range of wavelengths within the omnidirectional reflection band to the mid-range of wavelengths within the omnidirectional reflection band. This “range to mid-range ratio” (η) is mathematically expressed as:










η
TE

=

2





λ
long
TE



(


θ
0

=

90

°


)


-


λ
Short
TE



(


θ
0

=

0
0


)






λ
long
TE



(


θ
0

=

90
0


)


+


λ
Short
TE



(


θ
0

=

0
0


)









(
31
)








for the TE mode, and:










η
TM

=

2





λ
long
TM



(


θ
0

=

90

°


)


-


λ
Short
TM



(


θ
0

=

0
0


)






λ
long
TM



(


θ
0

=

90
0


)


+


λ
Short
TM



(


θ
0

=

0
0


)









(
32
)








for the TM mode. It is appreciated that the range to mid-range ratio can be expressed as a percentage and for the purposes of the present invention, the term range to mid-range ratio and range to mid-range ratio percentage are used interchangeably. It is further appreciated that a ‘range to mid-range ratio’ value provided herein having a ‘%’ sign following is a percentage value of the range to mid-range ratio. The range to mid-range ratios for the TM mode and TE mode can be numerically calculated from equations 31 and 32 and plotted as a function of high refractive index and low refractive index.


It is appreciated that to obtain the narrow omnidirectional band that the dispersion of the center wavelength must be minimized. Thus, from equation 30, the dispersion of the center wavelength can be expressed as:













Δλ
c

=




λ
c






θ
0

=

0
0






-

λ
c







θ
0

=

90
0











=



2


(




n
H



d
H


1

+



n
L



d
L


1

-



n
H



d
H




1
-


n
0
2


n
H
2





-



n
L



d
L




1
-


n
0
2


n
L
2






)









(
34
)








where:










Δλ
c

=



λ
0

4



F
c






(
35
)








and Fc, the center wavelength dispersion factor can be expressed as:










F
c

=

(

2
-

1


1
-


n
0
2


n
H
2





-

1


1
-


n
0
2


n
L
2






)





(
36
)







Given the above, a multilayer stack with a desired low center wavelength shift (Δλc) can be designed from a low index of refraction material having an index of refraction of nL and one or more layers having a thickness of dL and a high index of refraction material having an index of refraction of nH and one or more layers having a thickness of dH.


In particular, FIG. 4 provides a graphical representation of a comparison of the range to midrange ratio of 0.2% for the transverse magnetic mode and transverse electric mode of electromagnetic radiation plotted as a function of high refractive index versus low refractive index. As shown in the figure, three cases are illustrated in which Case I refers to a large difference between the transverse magnetic mode and the transverse electric mode, Case II refers to a situation for a smaller difference between the transverse magnetic mode and transverse electric mode, and Case III refers to a situation for a very small difference between the transverse magnetic mode and transverse electric mode. In addition, FIG. 5 illustrates a percent reflectance versus wavelength for reflected electromagnetic radiation for a case analogous with Case III.


As shown in FIG. 5, a small dispersion of the center wavelength for a multilayer thin film corresponding to Case III is shown. In addition, and with reference to FIG. 6, Case II provides a shift in the center wavelength of less than 50 nm (Case II) when a multilayer thin film structure is viewed between 0 and 45 degrees and Case III provides a center wavelength shift of less than 25 nm when the thin film structure is exposed to electromagnetic radiation between 0 and 45 degrees.


Second Generation

Referring now to FIG. 7, an illustrative structure/design according to a second generation is shown. The multilayer structure shown in FIG. 7 has a plurality of dielectric layers and an underlying absorbing layer. In addition, none of the incident electromagnetic radiation is transmitted through the structure, i.e. all of the incident electromagnetic radiation is reflected or absorbed. Such a structure as shown in FIG. 7 allows for the reduction of the number of dielectric layers that are needed in order to obtain a suitable amount of reflectance.


For example, FIG. 8 provides a schematic illustration of such a structure in which a multilayer stack has a central absorbing layer made from Cr, a first dielectric material layer (DL1) extending across the Cr absorbing layer, a second dielectric material layer (DL2) extending across the DL1 layer, and then another DL1 layer extending across the DL2 layer. In such a design, the thicknesses of the first dielectric layer and the third dielectric layer may or may not be the same.


In particular, FIG. 9A shows a graphical representation of a structure in which a central Cr layer is bounded by two TiO2 layers, which in turn are bounded by two SiO2 layers. As shown by the plot, the layers of TiO2 and SiO2 are not equal in thickness to each other. In addition, FIG. 9B shows a reflectance versus wavelength spectrum of the 5-layer structure shown in FIG. 9A and compared to a 13-layer structure made according to the first generation design. As illustrated in FIG. 9B, a shift in the center wavelength of less than 50 nm, and preferably less than 25 nm is provided when the structures are viewed a 0 and 45 degrees. Also shown in FIG. 9B is the fact that a 5-layer structure according to the second generation essentially performs equivalent to a 13-layer structure of the first generation.


Third Generation

Referring to FIG. 10, a third generation design is shown in which an underlying reflector layer (RL) has a first dielectric material layer DL1 extending thereacross and a selective absorbing layer SAL extending across the DL1 layer. In addition, another DL1 layer may or may not be provided and extend across the selective absorbing layer. Also shown in the figure is an illustration that all of the incident electromagnetic radiation is either reflected or selectively absorbed by the multilayer structure.


Such a design as illustrated in FIG. 10 corresponds to a different approach that is used for designing and manufacturing a desired multilayer stack. In particular, a zero or near-zero energy point thickness for a dielectric layer is used and discussed below.


For example, FIG. 11A is a schematic illustration of a ZnS dielectric layer extending across an Al reflector layer. The ZnS dielectric layer has a total thickness of 143 nm, and for incident electromagnetic radiation with a wavelength of 500 nm, a zero or near-zero energy point is present at 77 nm Stated differently, the ZnS dielectric layer exhibits a zero or near-zero electric field at a distance of 77 nm from the Al reflector layer for incident EMR having a wavelength of 500 nm In addition, FIG. 11B provides a graphical illustration of the energy field across the ZnS dielectric layer for a number of different incident EMR wavelengths. As shown in the graph, the dielectric layer has a zero electric field for the 500 nm wavelength at 77 nm thickness, but a non-zero electric field at the 77 nm thickness for EMR wavelengths of 300, 400, 600 and 700 nm.


Regarding calculation of a zero or near-zero electric field point, FIG. 12 illustrates a dielectric layer 4 having a total thickness ‘D’, an incremental thickness ‘d’ and an index of refraction ‘n’ on a substrate or core layer 2 having a index of refraction ns is shown. Incident light strikes the outer surface 5 of the dielectric layer 4 at angle θ relative to line 6, which is perpendicular to the outer surface 5, and reflects from the outer surface 5 at the same angle. Incident light is transmitted through the outer surface 5 and into the dielectric layer 4 at an angle θF relative to the line 6 and strikes the surface 3 of substrate layer 2 at an angle θs.


For a single dielectric layer, θsF and the energy/electric field (E) can be expressed as E(z) when z=d. From Maxwell's equations, the electric field can be expressed for s polarization as:

Ē(d)={u(z), 0, 0}exp (ikαy)|z=d   (37)

and for p polarization as:











E




(
d
)


=



{

0
,

u


(
z
)


,


-

α


ɛ
~



(
z
)






v


(
z
)




}



exp


(

i





k





α





y

)







z
=
d







(
38
)








where






k
=


2

π

λ






and λ is a desired wavelength to be reflected. Also, α=ns sin θs where ‘s’ corresponds to the substrate in FIG. 5 and {tilde over (ε)}(z) is the permittivity of the layer as a function of z. As such,

|E(d)|2=|u(z)|2 exp (2ikαy)|z=d   (39)

for s polarization and













E


(
d
)




2

=



[





u


(
z
)




2

+





α

n




v


(
z
)





2


]



exp


(

2

i





k





α





y

)







z
=
d







(
40
)








for p polarization.


It is appreciated that variation of the electric field along the Z direction of the dielectric layer 4 can be estimated by calculation of the unknown parameters u(z) and v(z) where it can be shown that:











(



u




v



)


z
=
d


=


(




cos





φ





(

i


/


q

)


sin





φ






i





q





sin





φ




cos





φ




)




(



u




v



)



z
=
0

,
substrate







(
41
)








Naturally, ‘i’ is the square root of −1. Using the boundary conditions u|z=0=1, v|z=0=qs, and the following relations:

qs=ns cos θs for s-polarization   (42)
qs=ns/cos θs for p-polarization   (43)
q=n cos θF for s-polarization   (44)
q=n/cos θF for p-polarization   (45)
φ=k·n·d cos (θF)   (46)

u(z) and v(z) can be expressed as:















u


(
z
)






z
=
d



=



u




z
=
0






cos





φ

+
v





z
=
o




(


i
q


sin





φ

)









=




cos





φ

+



i
·

q
s


q


sin





φ











and




(
47
)











v


(
z
)






z
=
d



=




i





q





u





z
=
0






sin





φ

+
v





z
=
0




cos





φ









=




i





q





sin





φ

+


q
s


cos





φ









(
48
)








Therefore:
















E


(
d
)




2

=




[



cos
2


φ

+



q
s
2


q
2




sin
2


φ


]



e

2

i





k





αγ









=




[



cos
2


φ

+



n
s
2


n
2




sin
2


φ


]



e

2

i





k





αγ










(
49
)








for s polarization with φ=k·n·d cos (θF), and:
















E


(
d
)




2

=



[



cos
2


φ

+



n
s
2


n
2




sin
2


φ

+



α
2

n



(



q
s
2



cos
2


φ

+


q
2



sin
2


φ


)



]







=



[



(

1
+



α
2



q
s
2


n


)



cos
2


φ

+


(



n
s
2


n
2


+



α
2



q
2


n


)



sin
2


φ


]








(
50
)








for p polarization where:









α
=



n
s


sin






θ
s


=

n





sin






θ
F







(
51
)








q
s

=


n
s


cos






θ
s









and




(
52
)







q
s

=

n

cos






θ
F







(
53
)







Thus for a simple situation where θF=0 or normal incidence, φ=k·n·d, and α=0:

















E


(
d
)




2






for





s


-


polarization

=







E


(
d
)




2






for





p


-


polarization







=



[



cos
2


φ

+



n
s
2


n
2




sin
2


φ


]







=




[



cos
2



(

k
·
n
·
d

)


+



n
s
2


n
2





sin
2



(

k
·
n
·
d

)




]



(
55
)









(
54
)








which allows for the thickness ‘d’ to be solved for, i.e. the position or location within the dielectric layer where the electric field is zero.


Referring now to FIG. 13, Equation 55 was used to calculate that the zero or near-zero electric field point in the ZnS dielectric layer shown in FIG. 11A when exposed to EMR having a wavelength of 434 nm is at 70 nm (instead of 77 nm for a 500 nm wavelength). In addition, a 15 nm thick Cr absorber layer was inserted at a thickness of 70 nm from the Al reflector layer to afford for a zero or near-zero electric field ZnS—Cr interface. Such an inventive structure allows light having a wavelength of 434 nm to pass through the Cr—ZnS interfaces, but absorbs light not having a wavelength of 434 nm Stated differently, the Cr—ZnS interfaces have a zero or near-zero electric field with respect to light having a wavelength of 434 nm and thus 434 nm light passes through the interfaces. However, the Cr—ZnS interfaces do not have a zero or near-zero electric field for light not having a wavelength of 434 nm and thus such light is absorbed by the Cr absorber layer and/or Cr—ZnS interfaces and not reflected by the Al reflector layer.


It is appreciated that some percentage of light within +/−10 nm of the desired 434 nm will pass through the Cr—ZnS interface. However, it is also appreciated that such a narrow band of reflected light, e.g. 434+/−10 nm, still provides a sharp structural color to a human eye.


The result of the Cr absorber layer in the multilayer stack in FIG. 13 is illustrated in FIG. 14 where percent reflectance versus reflected EMR wavelength is shown. As shown by the dotted line, which corresponds to the ZnS dielectric layer shown in FIG. 13 without a Cr absorber layer, a narrow reflected peak is present at about 400 nm, but a much broader peak is present at about 550+ nm. In addition, there is still a significant amount of light reflected in the 500 nm wavelength region. As such, a double peak that prevents the multilayer stack from having or exhibiting a structural color is present.


In contrast, the solid line in FIG. 14 corresponds to the structure shown in FIG. 13 with the Cr absorber layer present. As shown in the figure, a sharp peak at approximately 434 nm is present and a sharp drop off in reflectance for wavelengths greater than 434 nm is afforded by the Cr absorber layer. It is appreciated that the sharp peak represented by the solid line visually appears as sharp/structural color. Also, FIG. 14 illustrates where the width of a reflected peak or band is measured, i.e. the width of the band is determined at 50% reflectance of the maximum reflected wavelength, also known as full width at half maximum (FWHM).


Regarding omnidirectional behavior of the multilayer structure shown in FIG. 13, the thickness of the ZnS dielectric layer can be designed or set such that only the first harmonics of reflected light is provided. It is appreciated that this is sufficient for a “blue” color, however the production of a “red” color requires additional considerations. For example, the control of angular independence for red color is difficult since thicker dielectric layers are required, which in turn results in a high harmonic design, i.e. the presence of the second and possible third harmonics is inevitable. Also, the dark red color hue space is very narrow. As such, a red color multilayer stack has a higher angular variance.


In order to overcome the higher angular variance for red color, the instant application discloses a unique and novel design/structure that affords for a red color that is angular independent. For example, FIG. 15A illustrates a dielectric layer exhibiting first and second harmonics for incident white light when an outer surface of the dielectric layer is viewed from 0 and 45 degrees. As shown by the graphical representation, low angular dependence (small Δλc) is provided by the thickness of the dielectric layer, however, such a multilayer stack has a combination of blue color (1st harmonic) and red color (2nd harmonic)and thus is not suitable for a desired “red only” color. Therefore, the concept/structure of using an absorber layer to absorb an unwanted harmonic series has been developed. FIG. 15A also illustrates an example of the location of the reflected band center wavelength (λc) for a given reflection peak and the dispersion or shift of the center wavelength (Δλc) when the sample is viewed from 0 and 45 degrees.


Turning now to FIG. 15B, the second harmonic shown in FIG. 15A is absorbed with a Cr absorber layer at the appropriate dielectric layer thickness (e.g. 72 nm) and a sharp blue color is provided. More importantly for the instant invention, FIG. 15C illustrates that by absorbing the first harmonics with the Cr absorber at a different dielectric layer thickness (e.g. 125 nm) a red color is provided. However, FIG. 15C also illustrates that the use of the Cr absorber layer can result in more than desired angular dependence by the multilayer stack, i.e. a larger than desired Δλc . It is appreciated from FIGS. 15B and 15C that there is an outer dielectric layer extending over the CR absorber layer.


It is appreciated that the relatively large shift in λc for the red color compared to the blue color is due to the dark red color hue space being very narrow and the fact that the Cr absorber layer absorbs wavelengths associated with a non-zero electric field, i.e. does not absorb light when the electric field is zero or near-zero. As such, FIG. 16A illustrates that the zero or non-zero point is different for light wavelengths at different incident angles. Such factors result in the angular dependent absorbance shown in FIG. 16B, i.e. the difference in the 0° and 45° absorbance curves. Thus in order to further refine the multilayer stack design and angular independence performance, an absorber layer that absorbs, e.g. blue light, irrespective of whether or not the electric field is zero or not, is used.


In particular, FIG. 17A shows a multilayer stack with a Cu absorber layer instead of a Cr absorber layer extending across a dielectric ZnS layer. The results of using such a “colorful” or “selective” absorber layer is shown in FIG. 17B which demonstrates a much “tighter” grouping of the 0° and 45° absorbance lines for the multilayer stack shown in FIG. 17A. As such, a comparison between FIG. 16B and FIG. 16B illustrates the significant improvement in absorbance angular independence when using a selective absorber layer rather than non-selective absorber layer.


Based on the above, a proof of concept multilayer stack structure was designed and manufactured. In addition, calculation/simulation results and actual experimental data for the proof of concept sample were compared. In particular, and as shown by the graphical plot in FIG. 18, a sharp red color was produced (wavelengths greater than 700 nm are not typically seen by the human eye) and very good agreement was obtained between the calculation/simulation and experimental light data obtained from the actual sample. Stated differently, calculations/simulations can and/or are used to simulate the results of multilayer stack designs according to one or more embodiments of the present invention and/or prior art multilayer stacks.


A list of simulated and/or actually produced multilayer stack samples is provided in the Table 1 below. As shown in the table, the inventive designs disclosed herein include at least 5 different layered structures. In addition, the samples were simulated and/or made from a wide range of materials. Samples that exhibited high chroma, low hue shift and excellent reflectance were provided. Also, the three and five layer samples had an overall thickness between 120-200 nm; the seven layer samples had an overall thickness between 350-600 nm; the nine layer samples had an overall thickness between 440-500 nm; and the eleven layer samples had an overall thickness between 600-660 nm













TABLE 1






Ave. Chroma

Max.




(0-45)
Δh (0-65)
Reflectance
Sample Name



















 3 layer
90
2
96
3-1


 5 layer
91
3
96
5-1


 7 layer
88
1
92
7-1



91
3
92
7-2



91
3
96
7-3



90
1
94
7-4



82
4
75
7-5



76
20
84
7-6


 9 layer
71
21
88
9-1



95
0
94
9-2



79
14
86
9-3



90
4
87
9-4



94
1
94
9-5



94
1
94
9-6



73
7
87
9-7


11 layer
88
1
84
11-1 



92
1
93
11-2 



90
3
92
11-3 



89
9
90
11-4 









Turning now to FIG. 19, a plot of percent reflectance versus reflected EMR wavelength is shown for an omnidirectional reflector when exposed to white light at angles of 0 and 45° relative to the surface of the reflector. As shown by the plot, both the 0° and 45° curves illustrate very low reflectance, e.g. less than 20%, provided by the omnidirectional reflector for wavelengths greater than 500 nm However, the reflector, as shown by the curves, provides a sharp increase in reflectance at wavelengths between 400-500 nm and reaches a maximum of approximately 90% at 450 nm It is appreciated that the portion or region of the graph on the left hand side (UV side) of the curve represents the UV-portion of the reflection band provided by the reflector.


The sharp increase in reflectance provided by the omnidirectional reflector is characterized by an IR-sided edge of each curve that extends from a low reflectance portion at wavelengths greater than 500 nm up to a high reflectance portion, e.g. >70%. A linear portion 200 of the IR-sided edge is inclined at an angle (β) greater than 60° relative to the x-axis, has a length L of approximately 50 on the Reflectance-axis and a slope of 1.2. In some instances, the linear portion is inclined at an angle greater than 70° relative to the x-axis, while in other instances β is greater than 75°. Also, the reflection band has a visible FWHM of less than 200 nm, and in some instances a visible FWHM of less than 150 nm, and in other instances a visible FWHM of less than 100 nm In addition, the center wavelength λc for the visible reflection band as illustrated in FIG. 19 is defined as the wavelength that is equal-distance between the IR-sided edge of the reflection band and the UV edge of the UV spectrum at the visible FWHM.


It is appreciated that the term “visible FWHM” refers to the width of the reflection band between the IR-sided edge of the curve and the edge of the UV spectrum range, beyond which reflectance provided by the omnidirectional reflector is not visible to the human eye. In this manner, the inventive designs and multilayer stacks disclosed herein use the non-visible UV portion of the electromagnetic radiation spectrum to provide a sharp or structural color. Stated differently, the omnidirectional reflectors disclosed herein take advantage of the non-visible UV portion of the electromagnetic radiation spectrum in order to provide a narrow band of reflected visible light, despite the fact that the reflectors may reflect a much broader band of electromagnetic radiation that extends into the UV region.


Turning now to FIG. 20, a generally symmetrical reflection band provided by a multilayer stack according to an embodiment of the present invention and when viewed at 0° and 45° is shown. As illustrated in the figure, the reflection band provided by the multilayer stack when viewed at 0° has a center wavelength (λc(0°)) shifts less than 50 nm when the multilayer stack is viewed at 45° (λc(45°)), i.e. Δλc(0-45°)<50 nm In addition, the FWHM of both the 0° reflection band and the 45° reflection band is less than 200 nm.



FIG. 21 shows a plot of percent reflectance versus reflected EMR wavelength for another omnidirectional reflector design when exposed to white light at angles of 0 and 45° relative to the surface of the reflector. Similar to FIG. 19, and as shown by the plot, both the 0° and 45° curves illustrate very low reflectance, e.g. less than 10%, provided by the omnidirectional reflector for wavelengths less than 550 nm However, the reflector, as shown by the curves, provides a sharp increase in reflectance at wavelengths between 560-570 nm and reaches a maximum of approximately 90% at 700 nm It is appreciated 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 the reflector.


The sharp increase in reflectance provided by the omnidirectional reflector is characterized by a UV-sided edge of each curve that extends from a low reflectance portion at wavelengths below 550 nm up to a high reflectance portion, e.g. >70%. A linear portion 200 of the UV-sided edge is inclined at an angle (β) greater than 60° relative to the x-axis, has a length L of approximately 40 on the Reflectance-axis and a slope of 1.4. In some instances, the linear portion is inclined at an angle greater than 70° relative to the x-axis, while in other instances β is greater than 75°. Also, the reflection band has a visible FWHM of less than 200 nm, and in some instances a visible FWHM of less than 150 nm, and in other instances a visible FWHM of less than 100 nm In addition, the center wavelength λc for the visible reflection band as illustrated in FIG. 18 is defined as the wavelength that is equal-distance between the UV-sided edge of the reflection band and the IR edge of the IR spectrum at the visible FWHM.


It is appreciated that the term “visible FWHM” refers to the width of the reflection band between the UV-sided edge of the curve and the edge of the IR spectrum range, beyond which reflectance provided by the omnidirectional reflector is not visible to the human eye. In this manner, the inventive designs and multilayer stacks disclosed herein use the non-visible IR portion of the electromagnetic radiation spectrum to provide a sharp or structural color. Stated differently, the omnidirectional reflectors disclosed herein take advantage of the non-visible IR portion of the electromagnetic radiation spectrum in order to provide a narrow band of reflected visible light, despite the fact that the reflectors may reflect a much broader band of electromagnetic radiation that extends into the IR region.


Referring now to FIG. 22, a plot of percent reflectance versus wavelength is shown for another seven-layer design omnidirectional reflector when exposed to white light at angles of 0 and 45° relative to the surface of the reflector. In addition, a definition or characterization of omnidirectional properties provided by omnidirectional reflectors disclosed herein is shown. In particular, and when the reflection band provided by an inventive reflector has a maximum, i.e. a peak, as shown in the figure, each curve has a center wavelength (λc) defined as the wavelength that exhibits or experiences maximum reflectance. The term maximum reflected wavelength can also be used for λc.


As shown in FIG. 22, there is shift or displacement of λc when an outer surface of the omnidirectional reflector is observed from an angle 45°(λc(45°)), e.g. the outer surface is tiled 45° relative to a human eye looking at the surface, compared to when the surface is observed from an angle of 0°((λc(0°)), i.e. normal to the surface. This shift of λc (Δλc) provides a measure of the omnidirectional property of the omnidirectional reflector. Naturally a zero shift, i.e. no shift at all, would be a perfectly omnidirectional reflector. However, omnidirectional reflectors disclosed herein can provide a Δλc of less than 50 nm, which to the human eye can appear as though the surface of the reflector has not changed color and thus from a practical perspective the reflector is omnidirectional. In some instances, omnidirectional reflectors disclosed herein can provide a Δλc of less than 40 nm, in other instances a Δλc of less than 30 nm, and in still other instances a Δλc of less than 20 nm, while in still yet other instances a Δλc of less than 15 nm Such a shift in Δλc can be determined by an actual reflectance versus wavelength plot for a reflector, and/or in the alternative, by modeling of the reflector if the materials and layer thicknesses are known.


Another definition or characterization of a reflector's omnidirectional properties can be determined by the shift of a side edge for a given set of angle refection bands. For example, and with reference to FIG. 19, a shift or displacement of an IR-sided edge (ΔSIR) for reflectance from an omnidirectional reflector observed from 0° (SIR(0°)) compared to the IR-sided edge for reflectance by the same reflector observed from 45° (SIR(45°)) provides a measure of the omnidirectional property of the omnidirectional reflector. In addition, using ΔSIR as a measure of omnidirectionality can be preferred to the use of Δλc , e.g. for reflectors that provide a reflectance band similar to the one shown in FIG. 19, i.e. a reflection band with a peak corresponding to a maximum reflected wavelength that is not in the visible range (see FIGS. 19 and 21). It is appreciated that the shift of the IR-sided edge (ΔSIR) is and/or can be measured at the visible FWHM.


With reference to FIG. 21, a shift or displacement of a UV-sided edge (ΔSIR) for reflectance from an omnidirectional reflector observed from 0° (SUV(0°)) compared to the IR-sided edge for reflectance by the same reflector observed from 45° (SUV(45°)) provides a measure of the omnidirectional property of the omnidirectional reflector. It is appreciated that the shift of the UV-sided edge (ΔSUV) is and/or can be measured at the visible FWHM.


Naturally a zero shift, i.e. no shift at all (ΔSi=0 nm; i=IR, UV), would characterize a perfectly omnidirectional reflector. However, omnidirectional reflectors disclosed herein can provide a ΔSL of less than 50 nm, which to the human eye can appear as though the surface of the reflector has not changed color and thus from a practical perspective the reflector is omnidirectional. In some instances, omnidirectional reflectors disclosed herein can provide a ΔSi of less than 40 nm, in other instances a ΔSi of less than 30 nm, and in still other instances a ΔSi of less than 20 nm, while in still yet other instances a ΔSi of less than 15 nm Such a shift in ΔSi can be determined by an actual reflectance versus wavelength plot for a reflector, and/or in the alternative, by modeling of the reflector if the materials and layer thicknesses are known.


The shift of an omnidirectional reflection can also be measured by a low hue shift. For example, the hue shift of pigments manufactured from multilayer stacks according an embodiment of the present invention is 30° or less, as shown in FIG. 23 (see Δθ1), and in some instances the hue shift is 25° or less, preferably less than 20°, more preferably less than 15° and still more preferably less than 10°. In contrast, traditional pigments exhibit hue shift of 45° or more (see Δθ2).


In summary, a schematic illustration of an omnidirectional multilayer thin film according to an embodiment of the present invention in which a first layer 110 has a second layer 120 extending thereacross is shown in FIG. 24. An optional reflector layer 100 can be included. Also, a symmetric pair of layers can be on an opposite side of the reflector layer 100, i.e. the reflector layer 100 can have a first layer 110 oppositely disposed from the layer 110 shown in the figure such that the reflector layer 100 is sandwiched between a pair of first layers 110. In addition, a second layer 120 can be oppositely disposed the reflector layer 100 such that a five-layer structure is provided. Therefore, it should be appreciated that the discussion of the multilayer thin films provided herein also includes the possibility of a minor structure with respect to one or more central layers. As such, FIG. 24 can be illustrative of half of a five-layer multilayer stack.


The first layer 110 and second layer 120 can be dielectric layers, i.e. made from a dielectric material. In the alternative, one of the layers can be an absorbing layer, e.g. a selective absorbing layer or a non-selective absorbing layer. For example, the first layer 110 can be a dielectric layer and the second layer 120 can be an absorbing layer.



FIG. 25 illustrates half of a seven-layer design at reference numeral 20. The multilayer stack 20 has an additional layer 130 extending across the second layer 120. For example, the additional layer 130 can be a dielectric layer that extends across an absorbing layer 110. It is appreciated from FIG. 25 that layer 130 is an outer dielectric layer, i.e. there is not another layer extending over layer 130 and layer 130 can be the same or a different material as layer 110. In addition, layer 130 can be added onto the multilayer stack 20 using the same or a different method that used to apply layers 100, 110 and/or 120 such as with a sol gel process.



FIG. 26 illustrates half of a nine-layer design at reference numeral 24 in which yet an additional layer 105 is located between the optional reflector layer 100 and the first layer 110. For example, the additional layer 105 can be an absorbing layer 105 that extends between the reflector layer 100 and a dielectric layer 110. A non-exhaustive list of materials that the various layers can be made from are shown is shown in Table 2 below.










TABLE 2







Refractive Index Materials
Refractive Index Materials


(visible region)
(visible region)











Re-

Re-



fractive

fractive


Material
Index
Material
Index













Germanium (Ge)
4.0-5.0
Chromium (Cr)
3.0


Tellurium (Te)
4.6
Tin Sulfide (SnS)
2.6


Gallium Antimonite
4.5-5.0
Low Porous Si
2.56


(GaSb)

Chalcogenide glass
2.6


Indium Arsenide (InAs)
4.0
Cerium Oxide (CeO2)
2.53


Silicon (Si)
3.7
Tungsten (W)
2.5


Indium Phosphate (InP)
3.5
Gallium Nitride (GaN)
2.5


Gallium Arsenate (GaAs)
3.53
Manganese (Mn)
2.5


Gallium Phosphate (GaP)
3.31
Niobium Oxide
2.4


Vanadium (V)
3
(Nb2O3)



Arsenic Selenide
2.8
Zinc Telluride (ZnTe)
3.0


(As2Se3)

Chalcogenide glass +
3.0


CuAlSe2
2.75
Ag



Zinc Selenide (ZnSe)
2.5-2.6
Zinc Sulfate (ZnSe)
2.5-3.0


Titanium Dioxide
2.36
Titanium Dioxide
2.43


(TiO2)-solgel

(TiO2)-vacuum



Alumina Oxide (Al2O3)
1.75
deposited



Yttrium Oxide (Y2O3)
1.75
Hafnium Oxide (HfO2)
2.0


Polystyrene
1.6
Sodium Aluminum
1.6


Magnesium Fluoride
1.37
Fluoride (Na3AlF6)



(MgF2)

Polyether Sulfone (PES)
1.55


Lead Fluoride (PbF2)
1.6
High Porous Si
1.5


Potassium Fluoride (KF)
1.5
Indium Tin Oxide
1.46


Polyethylene (PE)
1.5
nanorods (ITO)



Barium Fluoride (BaF2)
1.5
Lithium Fluoride (LiF4)
1.45


Silica (SiO2)
1.5
Calcium Fluoride
1.43


PMMA
1.5
Strontium Fluoride
1.43


Aluminum Arsenate
1.56
(SrF2)



(AlAs)

Lithium Fluoride (LiF)
1.39


Solgel Silica (SiO2)
1.47
PKFE
1.6


N,N′ bis(1naphthyl)-
1.7
Sodium Fluoride (NaF)
1.3


4,4′Diamine (NPB)

Nano-porous Silica
1.23


Polyamide-imide (PEI)
1.6
(SiO2)



Zinc Sulfide (ZnS)
2.3 +
Sputtered Silica (SiO2)
1.47



i(0.015)
Vacuum Deposited
1.46


Titanium Nitride (TiN)
1.5 +
Silica (SiO2)




i(2.0) 
Niobium Oxide (Nb2O5)
2.1


Chromium (Cr)
2.5 +
Aluminum (Al)
2.0 +



i(2.5) 

i(15)


Niobium Pentoxide
2.4
Silicon Nitride (SiN)
2.1


(Nb2O5)

Mica
1.56


Zirconium Oxide (ZrO2)
2.36
Polyallomer
1.492


Hafnium Oxide (HfO2)
1.9-2.0
Polybutylene
1.50


Fluorcarbon (FEP)
1.34
Ionomers
1.51


Polytetrafluro-Ethylene
1.35
Polyethylene (Low
1.51


(TFE)

Density)



Fluorcarbon (FEP)
1.34
Nylons (PA) Type II
1.52


Polytetrafluro-
1.35
Acrylics Multipolymer
1.52


Ethylene(TFE)

Polyethylene
1.52


Chlorotrifiuoro-
1.42
(Medium Density)



Ethylene(CTFE)

Styrene Butadiene
1.52-1.55


Cellulose Propionate
1.46
Thermoplastic



Cellulose Acetate
1.46-1.49
PVC (Rigid)
1.52-1.55


Butyrate

Nylons (Polyamide)
1.53


Cellulose Acetate
1.46-1.50
Type 6/6



Methylpentene Polymer
1.485
Urea Formaldehyde
1.54-1.58


Acetal Homopolymer
1.48
Polyethylene
1.54


Acrylics
1.49
(High Density)



Cellulose Nitrate
1.49-1.51
Styrene Acrylonitrile
1.56-1.57


Ethyl Cellulose
1.47
Copolymer



Polypropylene
1.49
Polystyrene
1.57-1.60


Polysulfone
1.633
(Heat & Chemical)





Polystyrene
1.59




(General Purpose)





Polycarbornate
1.586




(Unfilled)





SnO2
2.0









Methods for producing the multilayer stacks disclosed herein can be any method or process known to those skilled in the art or one or methods not yet known to those skilled in the art. Typical known methods include wet methods such as sol gel processing, layer-by-layer processing, spin coating and the like. Other known dry methods include chemical vapor deposition processing and physical vapor deposition processing such as sputtering, electron beam deposition and the like.


The multilayer stacks disclosed herein can be used for most any color application such as pigments for paints, thin films applied to surfaces and the like.


The above examples and embodiments are for illustrative purposes only and changes, modifications, and the like will be apparent to those skilled in the art and yet still fall within the scope of the invention. As such, the scope of the invention is defined by the claims and all equivalents thereof.

Claims
  • 1. An omnidirectional structural color multilayer thin film comprising: a multilayer stack having a reflector layer, a dielectric layer extending over said reflector layer, an absorber layer extending over said dielectric layer and an outer dielectric layer extending over the absorber layer, said outer dielectric layer made from a dielectric material selected from the group consisting of ZnS and MgF2;said multilayer stack reflecting a band of visible electromagnetic radiation having a predetermined full width at half maximum (FWHM) of less than 200 nm and a predetermined color shift in the form of a hue shift of less than 30° on an a*b* color map when said multilayer stack is exposed to broadband electromagnetic radiation and viewed from angles between 0 and 45°.
  • 2. The multilayer thin film of claim 1, wherein said multilayer stack has a total thickness of less than 2 μm.
  • 3. The multilayer thin film of claim 2, wherein said total thickness of said multilayer stack is less than 1.5 μm.
  • 4. The multilayer thin film of claim 3, wherein said total thickness of said multilayer stack is less than 1.0 μm.
  • 5. The multilayer thin film of claim 1, wherein said color shift in the form of the hue shift of said reflected narrow band of visible electromagnetic radiation is less than 25° on the a*b* color map when said multilayer stack is exposed to broadband electromagnetic radiation and viewed from angles between 0 and 45°.
  • 6. The multilayer thin film of claim 1, wherein said dielectric layer has a thickness between 30-300 nm.
  • 7. The multilayer thin film of claim 1, wherein said absorber layer is a selective absorber layer.
  • 8. The multilayer thin film of claim 7, wherein said selective absorber layer is made from a material selected from the group consisting of Cu, Au, Zn, Sn, amorphous Si, crystalline Si and alloys thereof.
  • 9. The multilayer thin film of claim 7, wherein said selective absorber layer is made from a material selected from the group consisting of Fe2O3, Cu2O, amorphous Si, crystalline Si and combinations thereof.
  • 10. The multilayer thin film of claim 7, wherein said absorber layer has a thickness between 20-80 nm.
  • 11. The multilayer thin film of claim 1, wherein said absorber layer is a non-selective absorber layer.
  • 12. The multilayer thin film of claim 11, wherein said non-selective absorber layer is made from a material selected from a group consisting of Cr, Ta, W, Mo, Ti, Ti-nitride, Nb, Co, Si, Ge, Ni, Pd, V, ferric oxide, amorphous Si, crystalline Si and combinations or alloys thereof.
  • 13. The multilayer thin film of claim 11, wherein said non-selective absorber layer has a thickness between 5-30 nm.
  • 14. The multilayer thin film of claim 1, further comprising said multilayer stack reflecting a band of electromagnetic radiation in the UV range.
  • 15. The multilayer thin film of claim 1, further comprising said multilayer stack reflecting a band of electromagnetic radiation in the IR range.
  • 16. The multilayer thin film of claim 1, wherein said reflector layer is made from a metal selected from the group consisting of Al, Ag, Pt, Cr, Cu, Zn, Au, Sn, amorphous Si, crystalline Si and alloys thereof.
  • 17. The multilayer thin film of claim 16, wherein said reflector layer has a thickness between 50-200 nm.
  • 18. The multilayer thin film of claim 1, wherein said reflected narrow band of visible electromagnetic radiation has a symmetrical peak within a visible spectrum of electromagnetic radiation.
  • 19. The multilayer thin film of claim 1, wherein said reflected narrow band of visible electromagnetic radiation is bounded by a UV range of electromagnetic radiation.
  • 20. The multilayer thin film of claim 1, wherein said reflected narrow band of visible electromagnetic radiation is bounded by an IR range of electromagnetic radiation.
CROSS REFERENCE TO RELATED APPLICATIONS

The instant application is a continuation-in-part (CIP) of U.S. patent application Ser. No. 14/138,499 filed on Dec. 23, 2013, which in turn is a CIP of U.S. patent application Ser. No. 13/913,402 filed on Jun. 8, 2013, which in turn is a CIP of U.S. Patent application Ser. No. 13/760,699 filed on Feb. 6, 2013, which in turn is a CIP of Ser. No. 13/572,071 filed on Aug. 10, 2012, which in turn is a CIP of U.S. patent application Ser. No. 13/021,730 filed on Feb. 5, 2011, which in turn is a CIP of Ser. No. 12/793,772 filed on Jun. 4, 2010, which in turn is a CIP of U.S. patent application Ser. No. 12/388,395 filed on Feb. 18, 2009, which in turn is a CIP of U.S. patent application Ser. No. 11/837,529 filed Aug. 12, 2007 (U.S. Pat. No. 7,903,339). U.S. patent application Ser. No. 13/913,402 filed on Jun. 8, 2013 is a CIP of Ser. No. 13/014,398 filed Jan. 26, 2011, which is a CIP of Ser. No. 12/793,772 filed Jun. 4, 2010. U.S. patent application Ser. No. 13/014,398 filed Jan. 26, 2011 is a CIP of Ser. No. 12/686,861 filed Jan. 13, 2010 (U.S. Pat. No. 8,593,728), which is a CIP of Ser. No. 12/389,256 filed Feb. 19, 2009 (U.S. Pat. No. 8,329,247), all of which are incorporated in their entirety by reference.

US Referenced Citations (197)
Number Name Date Kind
3247392 Thelen Apr 1966 A
3650790 Klenke et al. Mar 1972 A
3769515 Clark, Jr. Oct 1973 A
3885408 Clark, Jr. May 1975 A
3910681 Elliott et al. Oct 1975 A
3953643 Cheung et al. Apr 1976 A
4079605 Bartels Mar 1978 A
4449126 Pekker May 1984 A
4525028 Dorschner Jun 1985 A
4544415 Franz et al. Oct 1985 A
4556599 Sato et al. Dec 1985 A
4643518 Taniguchi Feb 1987 A
4673914 Lee Jun 1987 A
4705839 Martin Nov 1987 A
4714308 Sawamura et al. Dec 1987 A
4753829 Panush Jun 1988 A
4756602 Southwell et al. Jul 1988 A
4868559 Pinnow Sep 1989 A
4896928 Perilloux et al. Jan 1990 A
5007710 Nakajima et al. Apr 1991 A
5043593 Tsutsumi et al. Aug 1991 A
RE33729 Perilloux Oct 1991 E
5132661 Pinnow Jul 1992 A
5138468 Barbanell Aug 1992 A
5183700 Austin Feb 1993 A
5214530 Coombs et al. May 1993 A
5245329 Gokcebay Sep 1993 A
5279657 Phillips et al. Jan 1994 A
5283431 Rhine Feb 1994 A
5323416 Bhat et al. Jun 1994 A
5423912 Sullivan et al. Jun 1995 A
5437931 Tsai et al. Aug 1995 A
5472798 Kumazawa et al. Dec 1995 A
5491470 Veligdan Feb 1996 A
5522923 Kimura et al. Jun 1996 A
5543665 Demarco Aug 1996 A
5561420 Kleefeldt et al. Oct 1996 A
5569332 Glatfelter et al. Oct 1996 A
5569535 Phillips et al. Oct 1996 A
5570847 Phillips et al. Nov 1996 A
5571624 Phillips et al. Nov 1996 A
5653792 Phillips et al. Aug 1997 A
5691844 Oguchi et al. Nov 1997 A
5700550 Uyama et al. Dec 1997 A
5759255 Venturini et al. Jun 1998 A
5768026 Kiyomoto et al. Jun 1998 A
5850309 Shirai et al. Dec 1998 A
5889603 Roddy et al. Mar 1999 A
5982078 Krisl et al. Nov 1999 A
6049419 Wheatley et al. Apr 2000 A
6055079 Hagans et al. Apr 2000 A
6130780 Joannopoulos et al. Oct 2000 A
6150022 Coulter et al. Nov 2000 A
6156115 Pfaff et al. Dec 2000 A
6157480 Anderson et al. Dec 2000 A
6157489 Bradley, Jr. et al. Dec 2000 A
6157498 Takahashi Dec 2000 A
6164777 Li et al. Dec 2000 A
6180025 Schoenfeld et al. Jan 2001 B1
6215592 Pelekhaty Apr 2001 B1
6242056 Spencer et al. Jun 2001 B1
6243204 Bradley, Jr. Jun 2001 B1
6249378 Shimamura et al. Jun 2001 B1
6310905 Shirai Oct 2001 B1
6331914 Wood, II et al. Dec 2001 B1
6383638 Coulter et al. May 2002 B1
6387457 Jiang et al. May 2002 B1
6387498 Coulter et al. May 2002 B1
6399228 Simpson Jun 2002 B1
6433931 Fink et al. Aug 2002 B1
6451414 Wheatley et al. Sep 2002 B1
6475273 Zimmermann et al. Nov 2002 B1
6534903 Spiro et al. Mar 2003 B1
6565770 Mayer et al. May 2003 B1
6569527 Calhoun et al. May 2003 B1
6574383 Erchak et al. Jun 2003 B1
6596070 Schmidt et al. Jul 2003 B1
6618149 Stilton Sep 2003 B1
6624945 Fan et al. Sep 2003 B2
6667095 Wheatley et al. Dec 2003 B2
6686042 LeGallee Feb 2004 B1
6844976 Firon et al. Jan 2005 B1
6873393 Ma Mar 2005 B2
6887526 Arlt et al. May 2005 B1
6894838 Mizrahi et al. May 2005 B2
6903873 Joannopoulos et al. Jun 2005 B1
6913793 Jiang et al. Jul 2005 B2
6927900 Liu et al. Aug 2005 B2
6997981 Coombs et al. Feb 2006 B1
7049003 Thomsen et al. May 2006 B2
7052762 Hebrink et al. May 2006 B2
7064897 Hebrink et al. Jun 2006 B2
7098257 Rink et al. Aug 2006 B2
7106516 Lotz et al. Sep 2006 B2
7123416 Erdogan et al. Oct 2006 B1
7141297 Condo et al. Nov 2006 B2
7169472 Raksha Jan 2007 B2
7184133 Coombs et al. Feb 2007 B2
7190524 Grawert et al. Mar 2007 B2
7215473 Fleming May 2007 B2
7236296 Liu et al. Jun 2007 B2
7267386 Hesch Sep 2007 B2
7326967 Hsieh et al. Feb 2008 B2
7329967 Nozawa et al. Feb 2008 B2
7352118 Chowdhury et al. Apr 2008 B2
7367691 Lin May 2008 B2
7410685 Rosenberger et al. Aug 2008 B2
7413599 Henglein et al. Aug 2008 B2
7446142 Meisenburg et al. Nov 2008 B2
7452597 Bujard Nov 2008 B2
7483212 Cho et al. Jan 2009 B2
7638184 Yaoita et al. Dec 2009 B2
7699927 Henglein et al. Apr 2010 B2
7745312 Herner et al. Jun 2010 B2
7847342 Fukuzumi et al. Dec 2010 B2
7851580 Li et al. Dec 2010 B2
7859754 Falicoff Dec 2010 B2
7863672 Jin et al. Jan 2011 B2
7903339 Banerjee et al. Mar 2011 B2
7929730 Huang et al. Apr 2011 B2
7980711 Takayanagi et al. Jul 2011 B2
8013383 Kidoh et al. Sep 2011 B2
8257784 Grayson et al. Sep 2012 B2
8313798 Nogueira et al. Nov 2012 B2
8323391 Banerjee et al. Dec 2012 B2
8329247 Banerjee et al. Dec 2012 B2
8350314 Fukuzumi et al. Jan 2013 B2
8440014 Kitamura et al. May 2013 B2
8446666 Kurt et al. May 2013 B2
8542441 Ouderkirk et al. Sep 2013 B2
8593728 Banerjee et al. Nov 2013 B2
8599464 Park Dec 2013 B2
8619365 Harris et al. Dec 2013 B2
8736959 Grayson et al. May 2014 B2
20010022151 Sliwinski et al. Sep 2001 A1
20020030882 Vitt et al. Mar 2002 A1
20020096087 Glausch Jul 2002 A1
20020117080 Okutsu et al. Aug 2002 A1
20020129739 Yanagimoto et al. Sep 2002 A1
20030002157 Someno Jan 2003 A1
20030059549 Morrow et al. Mar 2003 A1
20040047055 Mizrahi et al. Mar 2004 A1
20040156984 Vitt et al. Aug 2004 A1
20040179267 Moon et al. Sep 2004 A1
20040191540 Jakobi et al. Sep 2004 A1
20040246477 Moon et al. Dec 2004 A1
20040252509 Lin Dec 2004 A1
20040263983 Acree Dec 2004 A1
20040265477 Nabatova-Gabain et al. Dec 2004 A1
20050126441 Skelhorn Jun 2005 A1
20050132929 Raksha et al. Jun 2005 A1
20050152417 Lin Jul 2005 A1
20050235714 Lindstrom Oct 2005 A1
20050264874 Lin Dec 2005 A1
20060006402 Hsieh et al. Jan 2006 A1
20060023327 Coombs et al. Feb 2006 A1
20060030656 Tarng et al. Feb 2006 A1
20060081858 Lin et al. Apr 2006 A1
20060145172 Su et al. Jul 2006 A1
20060155007 Huber Jul 2006 A1
20060159922 O'Keefe Jul 2006 A1
20060222592 Burda Oct 2006 A1
20070097509 Nevitt et al. May 2007 A1
20070221097 Tarng et al. Sep 2007 A1
20090046368 Banerjee et al. Feb 2009 A1
20090082659 Ham et al. Mar 2009 A1
20090153953 Banerjee et al. Jun 2009 A1
20090161220 Banerjee et al. Jun 2009 A1
20090241802 Nemoto et al. Oct 2009 A1
20090303044 Furuichi et al. Dec 2009 A1
20090321693 Ohkuma et al. Dec 2009 A1
20100064938 Voit et al. Mar 2010 A1
20100208338 Banerjee et al. Aug 2010 A1
20100209593 Banerjee et al. Aug 2010 A1
20100213485 McKenzie et al. Aug 2010 A1
20110091658 Banerjee et al. Apr 2011 A1
20110113984 Fuller, Jr. et al. May 2011 A1
20110128616 Banerjee et al. Jun 2011 A1
20110134515 Banerjee et al. Jun 2011 A1
20110214733 den Boer et al. Sep 2011 A1
20110228399 Ohnishi Sep 2011 A1
20110299154 Grayson et al. Dec 2011 A1
20120050848 Carlson et al. Mar 2012 A1
20120107584 Eibon et al. May 2012 A1
20120307369 Banerjee et al. Dec 2012 A1
20130148221 Banerjee et al. Jun 2013 A1
20130213260 Kunii Aug 2013 A1
20130250403 Maeda Sep 2013 A1
20130265668 Banerjee et al. Oct 2013 A1
20140018439 Gruner et al. Jan 2014 A1
20140111861 Banerjee et al. Apr 2014 A1
20140368918 Banerjee et al. Dec 2014 A1
20150033988 Wu et al. Feb 2015 A1
20150138641 Deist et al. May 2015 A1
20150138642 Banerjee et al. May 2015 A1
20150309231 Banerjee Oct 2015 A1
20150309232 Banerjee Oct 2015 A1
Foreign Referenced Citations (74)
Number Date Country
1527100 Sep 2004 CN
1741246 Mar 2006 CN
101027365 Aug 2007 CN
101765791 Jun 2010 CN
102132214 Jul 2011 CN
102803174 Nov 2012 CN
103502333 Jan 2014 CN
103507322 Jan 2014 CN
103874939 Jun 2014 CN
104380150 Feb 2015 CN
104619668 May 2015 CN
2106613 Aug 1971 DE
19823732 Dec 1999 DE
141143 May 1985 EP
H0246366 Feb 1990 JP
H0312605 Jan 1991 JP
H05241017 Sep 1993 JP
H06016965 Jan 1994 JP
H06118229 Apr 1994 JP
07034324 Feb 1995 JP
H07258579 Oct 1995 JP
H8-259840 Oct 1996 JP
H10202813 Aug 1998 JP
H1112489 Jan 1999 JP
H11101913 Apr 1999 JP
H11504953 May 1999 JP
2000220331 Aug 2000 JP
2000329933 Nov 2000 JP
2002080749 Mar 2002 JP
2002090522 Mar 2002 JP
2003053875 Feb 2003 JP
2003329824 Nov 2003 JP
2004505158 Feb 2004 JP
2004134743 Apr 2004 JP
2004510013 Apr 2004 JP
2004512394 Apr 2004 JP
2005513207 May 2005 JP
2005144925 Jun 2005 JP
2006506518 Feb 2006 JP
2006097426 Apr 2006 JP
3799696 Jul 2006 JP
2006193738 Jul 2006 JP
2006285196 Oct 2006 JP
2007065232 Mar 2007 JP
2007510022 Apr 2007 JP
2007133325 May 2007 JP
2007183525 Jul 2007 JP
2008038382 Feb 2008 JP
2008508404 Mar 2008 JP
2008510866 Apr 2008 JP
2008526002 Jul 2008 JP
2008191592 Aug 2008 JP
2008209520 Sep 2008 JP
2008230218 Oct 2008 JP
2008257777 Oct 2008 JP
2009427633 Feb 2009 JP
2009511725 Mar 2009 JP
2010502433 Jan 2010 JP
2010526015 Jul 2010 JP
2010191431 Sep 2010 JP
4948706 Jun 2012 JP
2013518946 May 2013 JP
2014237819 Dec 2014 JP
2015120350 Jul 2015 JP
2016027095 Feb 2016 JP
2016049777 Apr 2016 JP
9936258 Jan 1999 WO
9942892 Aug 1999 WO
0012634 Mar 2000 WO
2000022466 Apr 2000 WO
0031571 Jun 2000 WO
02054030 Jul 2002 WO
03062871 Jul 2003 WO
2015153043 Oct 2015 WO
Non-Patent Literature Citations (73)
Entry
Distributed Bragg Reflector; en.wikipedia.org/wiki/Bragg_reflector.
Kate Kaminska et al., Birefringent Omnidirectional Reflector; Applied Optics; vol. 43, No. 7; Mar. 2004.
M. Deopura et al., Dielectric Omnidirectional Visible Reflector; Optical Society of America; vol. 26, No. 15; Department of Material Science and Engineering, Massachusetts Institute of Technology; pp. 1197-1199.
Optical Coating Design Algorithm Based on the Equivalent Layers Theory; Alexander V. Tikhonravov et al; Applied Optics; vol. 45, No. 7; Mar. 2006.
Photonic Crystal; en.wikipedia.org/wiki/Photonic_crystals.
Sajeev John et al., Photonic Band Gap Materials; A Semiconductor for Light; Department of Physics, University of Toronto, p. 1-23.
Tikhonravov, et al., “Application of the Needle Optimization Technique to the Design of Optical Coatings”, Applied Optics, Optical Society of America, 1996, pp. 5493-5508, vol. 35, No. 28.
Bing-Xin Wei et al., “Detrimental Thixotropic Thinning of Filter Cake of SiO2—Al2O3 Composite Coated TiO2 and Particles Its Control”, Industrial & Engineering Chemistry Research, Sep. 27, 2011, 50, pp. 13799-13804.
Tikhonravov, Alexander V. et al., “Optical Coating Design Algorithm Based on the Equivalent Layers Theory”, Applied Optics: vol. 45, No. 7; Mar. 2006; pp. 1530-1538.
Kaminska, Kate et al., “Birefringent Omnidirectional Reflector”, Applied Optics, vol. 43, No. 7, Mar. 2004, pp. 1570-1576.
Hongqiang et al, “Disordered dielectric high reflectors with broadband from visible to infrared,” Applied Physics Letters, American Institute of Physics, Melville, NY, US, vol. 74, No. 22, dated May 31, 2009.
Xifre-Perez et al, “Porous silicon mirrors with enlarged omnidirectional band gap,” Journal of Applied Physics, American Institute of Physics, Melville, NY, US, vol. 97, No. 6, dated Mar. 9, 2005.
“Laser 2000 Gmbttp://www.laser2000.de/fileadmin/Produkdaten/SK_WEB/Datenblaetter_SEM/SEMROCK-StopLine-Notchfilter.pdf, accessed Feb. 2, 2010”.
Bendiganavale A.K., Malshe, V.C., “Infrared Reflective Inorganic Pigments”, Recent Patents on Chemical Engineering, Jan. 2008, 67-79.
D.P. Young, Jr., et al. “Comparison of Avian Responses to UV-Light Reflective Paint on Wind Turbines,” National Renewable Energy Laboratory, Subcontract Report, Jan. 2003.
Maier, E.J. “To Deal With the Invisible”: On the biological significance of ultraviolet sensitivity in birds. Naturwissenschaften 80: 476-478, 1993.
Nison, J., “Twinkle, Twinkle Little Star,” Asia Pacific Coating Journal, Feb. 2004.
Fink, Joel “A Dielectric Omnidirectional Reflector”, E.L. Thomas, Science, vol. 282, (Nov. 27, 1988).
Lin, Weihua, “Design and Fabrication of Omnidirectional Reflectors in the Visible Range” Journal of Modern Optics, vol. 52, No. 8, 1155 (2005).
Chen, Kevin M. “Si02/Ti02 Omnidirectional Reflector and Microcavity Resonator Via the Sol-Gel Method”, Appl. Phys. Lett., vol. 75, No. 24, Dec. 13, 1999.
Almedia, R.M., “Photonic Bandgap Materials and Structures by Sol-Gel Processing”, Journal of Non-Crystalline Solids, 405-499 (2003).
Deopura, M. “Dielectric Omnidirectional Visible Reflector,” Optics Letters, Aug. 1, 2001, vol. 16, No. 15.
Decourby, R.G., “Planar Omnidirectional Reflectors in Chalcogenide Glass and Polymer” Optics Express, 6228, Aug. 8, 2005.
Clement, T.J., “Improved Omnidirectional Reflectors in Chalcogenide Glass and Polymer by Using the Silver Doping Tachnique”, Optics Express, 14, 1789 (2006).
Bryant, A., “All-Silicon Omnidirectional Mirrors Based on One-Dimensional Crystals”, Appl. Phys. Lett. vol. 82, No. 19, May 12, 2003.
Chigrin, D.N., “Observation of Total Omnidirectional Reflection From a One-Dimensional Dielectric Lattice”, Appl. Phys. A. 68, 25-28 (1999).
Park, Y., “GaAs-based Near-infrared Omnidirectional Reflector”, Appl. Phys. Lett., vol. 82, No. 17, Apr. 28, 2003.
H-Y Lee, “Design and Evaluation of Omnidirectional One-Dimensional Photonic Crystals”, Journal of Appl. Phys. vol. 93, No. 2, Jan. 15, 2003.
Banerjee, Debasish, “Narrow-band Omnidirectional Structural Color”, SAE World Congress 01-1049 (2008).
Schmid, Raimund and Mronga, Norbert, “A New Generation of Sparkling Effect Pigments”, Paint & Coatings Industry; Oct. 2004, vol. 20 Issue 10, p. 118-121.
Office Action dated Sep. 5, 2018 pertaining to Japanese Patent Application No. 2014-117702.
Office Action dated Jun. 4, 2019 pertaining to Japanese Patent Application No. 2014-117702.
Office Action dated Sep. 30, 2018 pertaining to Chinese Patent Application No. 201410693385.4.
Office Action dated Apr. 22, 2019 pertaining to Chinese Patent Application No. 201410693385.4.
Office Action dated Sep. 21, 2018 pertaining to German Patent Application No. 10 2014 119 261.3.
Office Action dated Feb. 5, 2019 pertaining to Japanese Patent Application No. 2016-559529.
Office Action dated Jul. 12, 2018 pertaining to Chinese Patent Application No. 201580026216.8.
Office Action dated Apr. 1, 2019 pertaining to Chinese Patent Application No. 201580026216.8.
Office Action dated Oct. 9, 2019 pertaining to Chinese Patent Application No. 201580026216.8.
International Preliminary Report on Patentability dated Oct. 4, 2016 pertaining to PCT/US2015/018640, filed Mar. 1, 2015.
International Search Report and Written Opinion dated May 29, 2015 pertaining to PCT/US2015/018640, filed Mar. 4, 2015.
Office Action dated Nov. 2, 2018 pertaining to Chinese Patent Application No. 201510498432.4.
Office Action dated Jun. 28, 2019 pertaining to Chinese Patent Application No. 201510498432.4.
Office Action dated Dec. 3, 2019 pertaining to Chinese Patent Application No. 201510498432.4.
Office Action dated May 28, 2019 pertaining to Japanese Patent Application No. 2015-160731.
Office Action dated Mar. 20, 2018 pertaining to Japanese Patent Application No. 2015-169044.
Office Action dated Feb. 8, 2018 pertaining to German Patent Application No. 102015113535.3.
Office Action dated Sep. 4, 2018 pertaining to Chinese Patent Application No. 201510624641.9.
Office Action dated Nov. 5, 2019 pertaining to Japanese Patent Application No. 2016-014076.
Office Action dated Jul. 16, 2019 pertaining to Chinese Patent Application No. 201610040211.7.
Office Action dated Oct. 29, 2018 pertaining to Chinese Patent Application No. 201610397388.2.
Office Action dated Jun. 4, 2019 pertaining to Chinese Patent Application No. 201610397388.2.
Office Action dated May 29, 2018 pertaining to Japanese Patent Application No. 2016-113282.
Office Action dated Apr. 16, 2019 pertaining to Japanese Patent Application No. 2016-113282.
Office Action dated Oct. 29, 2018 pertaining to Chinese Patent Application No. 201610397718.8.
Office Action dated Jun. 5, 2018 pertaining to Japanese Patent Application No. 2016-113434.
Office Action dated Oct. 25, 2018 pertaining to Chinese Patent Application No. 201610395759.3.
Office Action dated Jun. 4, 2019 pertaining to Chinese Patent Application No. 201610395759.3.
Office Action dated May 29, 2018 pertaining to Japanese Patent Application No. 2016-113285.
Office Action dated Apr. 16, 2019 pertaining to Japanese Patent Application No. 2016-113285.
Office Action dated Jul. 10, 2019 pertaining to Chinese Patent Application No. 201710284783.4.
Office Action dated Sep. 18, 2018 pertaining to Japanese Patent Application No. 2017-085886.
Office Action dated Jun. 4, 2019 pertaining to Japanese Patent Application No. 2017-085886.
Office Action dated Jan. 23, 2013 pertaining to Japanese Patent Application No. 2008-208255.
Office Action dated Feb. 26, 2014 pertaining to Japanese Patent Application No. 2008-208255.
Office Action dated Sep. 30, 2014 pertaining to Japanese Patent Application No. 2008-208255.
Office Action dated Jan. 30, 2017 pertaining to Japanese Patent Application No. 2010-114777.
Office Action dated Jan. 29, 2015 pertaining to Japanese Patent Application No. 2011-126545.
Office Action dated Jun. 23, 2015 pertaining to Japanese Patent Application No. 2011-126545.
Office Action dated Jan. 27, 2014 pertaining to Japanese Patent Application No. 2011-213056.
Office Action dated Nov. 20, 2014 pertaining to Japanese Patent Application No. 2011-213056.
Office Action dated Aug. 15, 2017 pertaining to Japanese Patent Application No. 2013-167895.
Office Action dated Feb. 20, 2018 pertaining to Japanese Patent Application No. 2013-167895.
Related Publications (1)
Number Date Country
20140211303 A1 Jul 2014 US
Continuation in Parts (12)
Number Date Country
Parent 14138499 Dec 2013 US
Child 14242429 US
Parent 13913402 Jun 2013 US
Child 14138499 US
Parent 13760699 Feb 2013 US
Child 13913402 US
Parent 13572071 Aug 2012 US
Child 13760699 US
Parent 13021730 Feb 2011 US
Child 13572071 US
Parent 12793772 Jun 2010 US
Child 13021730 US
Parent 12388395 Feb 2009 US
Child 12793772 US
Parent 11837529 Aug 2007 US
Child 12388395 US
Parent 13014398 Jan 2011 US
Child 13913402 Jun 2013 US
Parent 12793772 US
Child 13014398 US
Parent 12686861 Jan 2010 US
Child 12793772 US
Parent 12389256 Feb 2009 US
Child 12686861 US