UV-REFLECTIVE STRUCTURAL COLOR

• US 20100290109A1
• Filed: 05/18/2009
• Published: 11/18/2010
• Est. Priority Date: 05/18/2009
• Status: Active Grant

• Current Assignee: Toyota Motor Corporation
• Original Assignee: Massachusetts Institute of Technology, Toyota Motor Corporation, Toyota Motor Engineering & Manufacturing North America Incorporated (Toyota Motor Corporation)
• Inventors: Cohen, Robert E., Kurt, Pinar, Rubner, Michael, Banerjee, Debasish, Zhang, Minjuan, Ishii, Masahiko
• Granted Patent: US 8,446,666 B2
• Time in Patent Office: Days
• US Class Current: 359/359
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 23/053 Producing by wet processes, e.g. hydrolysing titanium salts
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C09C 1/0051 comprising a stack of coating layers with alternating low and high refractive indices, wherein the first coating layer on the core surface has the low refractive index
• CPC Class Codes: C09C 2200/409 Mixed inorganic-organic coating
• CPC Class Codes: C09C 2200/505 Inorganic particles, e.g. oxides, nitrides or carbides
• CPC Class Codes: C09C 2210/20 Optical properties in the UV-range
• CPC Class Codes: G02B 5/0891 Ultraviolet [UV] mirrors apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation

Abstract

The present invention discloses a non-quarter wave multilayer structure having a plurality of alternating low index of refraction material stacks and high index of refraction material stacks. The plurality of alternating stacks can reflect electromagnetic radiation in the ultraviolet region and a narrow band of electromagnetic radiation in the visible region. The non-quarter wave multilayer structure, i.e. n_Ld_L≠n_Hd_H≠λ₀/4, can be expressed as [A 0.5qH pL(qH pL)^N 0.5qH G], where q and p are multipliers to the quarter-wave thicknesses of high and low refractive index material, respectively, H is the quarter-wave thickness of the high refracting index material; L is the quarter-wave thickness of the low refracting index material; N represents the total number of layers between bounding half layers of high index of refraction material (0.5qH); G represents a substrate and A represents air.

Claims

1. A multilayer structure comprising:

a plurality of alternating layers of a low index of refraction material and a high index of refraction material;

said plurality of alternating layers of said low index of refraction material and said high index of refraction material reflecting electromagnetic radiation in the ultraviolet region and a narrow band of electromagnetic radiation in the visible region.

2. The multilayer structure of claim 1, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material each have a non-quarter wave thickness.

3. The multilayer structure of claim 1, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material has a layered structure described by [A 0.5qH pL (qH pL)^N 0.5qH G], where:

A represents air;

q is a multiplier of a quarter-wave thickness of said high index of refraction material;

H is the quarter wave thickness of the high refracting index material for a given wavelength λ

₀;

p is a multiplier of a quarter-wave thickness of said low index of refraction material;

L is the thickness of the low refracting index material for said given wavelength λ

₀;

N represents the total number of layers between bounding half layers of said high index of refraction material; and

G represents a substrate.

4. The multilayer structure of claim 1, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material reflect more than 70% of said electromagnetic radiation in the ultraviolet region and more than 60% of said narrow band of electromagnetic radiation in the visible region.

5. The multilayer structure of claim 1, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material are made by a layer-by-layer process.

6. The multilayer structure of claim 5, wherein said low index of refraction material is made from SiO₂ nanoparticles and said high index of refraction material is made from TiO₂ nanoparticles.

7. The multilayer structure of claim 1, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material are in the form of a flake.

8. The multilayer structure of claim 7, wherein said flake is a pigment for a paint.

9. A multilayer structure comprising:

a plurality of alternating layers of a low index of refraction material and a high index of refraction material;

said plurality of alternating layers of said low index of refraction material and said high index of refraction material having a layered structure described by [A 0.5qH pL (qH pL)^N 0.5qH G], where;

A represents air;

q is a multiplier of a quarter-wave thickness of said high index of refraction material;

H is the quarter wave thickness of the high refracting index material for a given wavelength λ

₀;

p is a multiplier of a quarter-wave thickness of said low index of refraction material;

L is the quarter wave thickness of the low refracting index material for said given wavelength λ

₀;

N represents the total number of layers between bounding half layers of said high index of refraction material; and

G represents a substrate;

said plurality of alternating layers of said low index of refraction material and said high index of refraction material also operable to reflect electromagnetic radiation in the ultraviolet region and a narrow band of electromagnetic radiation in the visible region.

10. The multilayer structure of claim 9, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material reflect more than 70% of said electromagnetic radiation in the ultraviolet region and more than 60% of said narrow band of electromagnetic radiation in the visible region.

11. The multilayer structure of claim 9, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material are made by a layer-by-layer process.

12. The multilayer structure of claim 11, wherein said low index of refraction material is made from SiO₂ nanoparticles and said high index of refraction material is made from TiO₂ nanoparticles.

13. The multilayer structure of claim 9, wherein said plurality of alternating layers of said low index of refraction material and said high index of refraction material are in the form of a flake.

14. The multilayer structure of claim 13, wherein said flake is a pigment for a paint.

15. The multilayer structure of claim 14, wherein said paint is an ultraviolet reflective structural color.

16. A process for making a multilayer structure that is an ultraviolet-reflective structural color, the process comprising:

providing a low index of refraction material and a high index of refraction material;

fabricating a first layer from the low index of refraction material;

fabricating a second layer from the high index of refraction material adjacent to and in contact with the first layer;

the first layer and the second layer having a thickness of pL and qH, respectively, where;

L is a quarter wave thickness (λ

_o/4n_L) of the low index of refraction material for a desired reflected wavelength λ

_o;

H is a quarter wave thickness (λ

_o/4n_H) of the high index of refraction material for the same desired reflected wavelength λ

_o;

p and q are multiplies to the quarter wave thickness L and H, respectively; and

p and q satisfy the expression;

2n_LL_p cos(θ

_L)+2 n_HHq cos(θ

_H)=Mλ

where;

n_L is the index of refraction for the low index of refraction material;

n_H is the index of refraction for the high index of refraction material;

θ

_L is the angle of refraction for the low index of refraction material;

θ

_H is the angle of refraction for the high index of refraction material;

M is an integer (1, 2, 3, . . . ); and

λ

are the peaks to be reflected.

17. The process of claim 16, further including fabricating a plurality of alternating first layers and second layers.

18. The process of claim 17, wherein the plurality of alternating first layers and second layers are described by [A 0.5qH pL (qH pL)^N 0.5qH G];

where;

A represents air;

N represents the total number of layers between bounding half layers of said high index of refraction material; and

G represents a substrate.

19. The process of claim 17, wherein the plurality of first layers and second layers are fabricated using layer-by-layer processing.