Optical element and method for manufacturing the same

1. An optical element comprising:

a first optical layer having a concavo-convex surface;

a wavelength-selective reflective layer provided on the concavo-convex surface of the first optical layer; and

a second optical layer provided on the concavo-convex surface on which the wavelength-selective reflective layer is provided so as to fill the concavo-convex surface,

wherein the wavelength-selective reflective layer includes

a metal layer,

a protective layer provided on the metal layer and containing a metal oxide as a primary component, and

a high refractive index layer provided on the protective layer and containing a metal oxide other than zinc oxide as a primary component, and

the wavelength-selective reflective layer selectively directionally reflects light in a specific wavelength band while transmitting light other than that in the specific wavelength band.

2. The optical element according to claim 1 , wherein, of light incident on an incident surface at an incident angle (θ, φ) (where, θ is an angle formed between a normal to the incident surface and incident light incident on the incident surface or reflected light emitted from the incident surface, and φ is an angle formed between a specific straight line within the incident surface and a component of the incident light or the reflected light projected on the incident surface), the optical element selectively directionally reflects light in a specific wavelength band in a direction other than a specular reflection direction (−θ,φ+180°) while transmitting light other than that in the specific wavelength band and having transparency to the light other than that in the specific wavelength band.

3. The optical element according to claim 1 , wherein the high refractive index layer contains at least one selected from the group consisting of niobium oxide, tantalum oxide, and titanium oxide.

4. The optical element according to claim 1 , wherein the protective layer contains as a primary component a metal oxide at least containing zinc oxide.

5. The optical element according to claim 4 , wherein the protective layer contains at least one metal oxide selected from the group consisting of zinc oxide (ZnO), Ga and Al-doped zinc oxide (GAZO), Al-doped zinc oxide (AZO), and Ga-doped zinc oxide (GZO).

6. The optical element according to claim 1 , wherein the metal layer contains at least one selected from the group consisting of Au, Ag, Cu, Al, Ni, Cr, Ti, Pd, Co, Si, Ta, W, Mo, and Ge.

7. The optical element according to claim 1 , wherein the protective layer has a thickness in a range of 3 to 30 nm.

8. The optical element according to claim 1 , wherein the high refractive index layer has a thickness in a range of 10 to 120 nm.

9. The optical element according to claim 1 , wherein the metal layer has a thickness in a range of 6 to 30 nm.

10. The optical element according to claim 1 , wherein the concavo-convex surface of the first optical layer is formed of one-dimensionally or two-dimensionally arranged structures.

11. The optical element according to claim 10 , wherein the structures each have a prism shape, a lenticular shape, a hemispherical shape, or a corner cube shape.

12. The optical element according to claim 1 , wherein the wavelength-selective reflective layer includes at least two repeating units laminated to each other, the repeating units each containing the metal layer, the protective layer, and the high refractive index layer.

13. The optical element according to claim 1 , further comprising another high refractive index layer between the concavo-convex surface of the first optical layer and the metal layer of the wavelength-selective reflective layer.

14. The optical element according to claim 13 , wherein the another high refractive index layer contains at least one selected from the group consisting of niobium oxide, tantalum oxide, and titanium oxide.

15. A method for manufacturing an optical element comprising:

forming a wavelength-selective reflective layer on a concavo-convex surface of a first optical layer; and

forming a second optical layer on the concavo-convex surface on which the wavelength-selective reflective layer is formed so as to fill the concavo-convex surface,

wherein the step of forming a wavelength-selective reflective layer includes the substeps of:

forming a metal layer;

forming a protective layer containing a metal oxide as a primary component on the metal layer; and

forming a high refractive index layer containing a metal oxide other than zinc oxide as a primary component on the protective layer, and

the wavelength-selective reflective layer selectively directionally reflects light in a specific wavelength band while transmitting light other than that in the specific wavelength band.

16. The method for manufacturing an optical element according to claim 15 , wherein in the substep of forming a protective layer, the protective layer is formed by a sputtering method using a target containing the metal oxide as a primary component.

17. The method for manufacturing an optical element according to claim 15 , wherein in the substep of forming a protective layer, the protective layer is formed by a sputtering method using only an inert gas as a process gas.

18. The method for manufacturing an optical element according to claim 15 , wherein the high refractive index layer contains at least one selected from the group consisting of niobium oxide, tantalum oxide, and titanium oxide.