Wavelength-selective absorptive material, infrared sensor, wavelength-selective light source, and radiation cooling system
Provided is a wavelength-selective absorptive material which includes, in the following order: a base material; a reflective layer; and a high refractive index layer having a refractive index n of 3.0 or more with respect to infrared light having a wavelength range of 8 μm to 13 μm, having a thickness d of 30 nm to 1,000 nm, and containing a binder and flat metal particles; and an infrared absorptive layer having a maximum absorption wavelength in a wavelength range of 8 μm to 13 μm, in which a product n×d of the refractive index n and the thickness d is more than 1,000 and less than 4,875.
1. A wavelength-selective absorptive material comprising, in the following order:
a base material;
a reflective layer;
a high refractive index layer having a refractive index n of 3.0 or more with respect to infrared light having a wavelength range of 8 μm to 13 μm, having a thickness d of 30 nm to 1,000 nm, and containing a binder and flat metal particles A; and
an infrared absorptive layer having a maximum absorption wavelength in the wavelength range of 8 μm to 13 μm,
wherein a product n×d of the refractive index n and the thickness d is more than 1,000 and less than 4,875.
2. The wavelength-selective absorptive material according to claim 1 , wherein the infrared absorptive layer contains particles B having a maximum absorption wavelength in the wavelength range of 8 μm to 13 μm.
3. The wavelength-selective absorptive material according to claim 2 , wherein the particles B have a reststrahlen band, which results from phonon oscillation, in the wavelength range of 8 μm to 13 μm.
4. The wavelength-selective absorptive material according to claim 2 , wherein the particles B include a SiO 2 particle, a SiC particle, or a SiN particle.
5. The wavelength-selective absorptive material according to claim 2 , wherein a volume content proportion of the particles B is 1% by volume to 50% by volume with respect to an entire infrared absorptive layer.
6. The wavelength-selective absorptive material according to claim 1 , wherein a value obtained by dividing an average particle size of the flat metal particles A by an average thickness thereof is 5 or more, principal planes of the flat metal particles A are plane-oriented in a range of 0° to 30° with respect to a surface of the high refractive index layer, a volume fraction of the flat metal particles A in the high refractive index layer is 30% by volume or more, and the flat metal particles A are laminated in two or more layers.
7. The wavelength-selective absorptive material according to claim 1 , wherein the flat metal particles A contain at least silver.
8. The wavelength-selective absorptive material according to claim 1 , wherein a shape of a principal plane of each flat metal particle A is a polygonal shape of a hexagonal shape or a higher polygonal shape, or a circular shape.
9. An infrared sensor comprising:
the wavelength-selective absorptive material according to claim 1 .
10. A wavelength-selective light source comprising:
the wavelength-selective absorptive material according to claim 1 .
11. A radiation cooling system comprising:
the wavelength-selective absorptive material according to claim 1 .