Optical body, window material, and roll screen
An optical body includes a first optical transparent layer having quadrangular pyramid-shaped depressions, a wavelength-selective reflecting layer formed on the depressions and selectively reflecting light of a specific wavelength band, and a second optical transparent layer formed on the wavelength-selective reflecting layer. When (θ, ϕ) is taken as the incident angle (θ: angle between perpendicular line relative to second optical transparent layer acting as incident surface and light incident on incident surface; ϕ: angle between specific straight line within incident surface and component resulting from projection of incident light on incident surface), with respect to incident light that is incident on the incident surface from different ϕ directions at θ=60°, the optical body has an average reflection angle of reflected light to the same quadrant as the incident light of 30° or more.
1. An optical body comprising:
a first optical transparent layer having a surface in which quadrangular pyramid-shaped depressions having ridges that rhombically intersect are formed;
a wavelength-selective reflecting layer that is formed on the depressions and selectively reflects light of a specific wavelength band; and
a second optical transparent layer formed on the wavelength-selective reflecting layer, wherein
when (θ, ϕ) is taken as an incident angle, where:
θ is an angle between a perpendicular line relative to the second optical transparent layer acting as an incident surface and incident light that is incident on the incident surface; and
ϕ is an angle between a specific straight line within the incident surface and a component resulting from projection of the incident light on the incident surface,
with respect to incident light that is incident on the incident surface from different directions at θ=60°, an average reflection angle of reflected light to the same quadrant as the incident light is 30° or more, and
wherein equations (1) shown below,
25°≤θ1≤45° and θ2≤15° (1)
are satisfied when:
an intersection angle of the ridges that rhombically intersect is taken to be θ1; and
an angle between a principal axis of each of the depressions that passes through a lowermost point of the depression and a center of mass of a rhombic open surface of the depression and the perpendicular line is taken to be θ2.
2. The optical body according to claim 1 , wherein
the wavelength-selective reflecting layer includes at least an amorphous high refractive index layer and a metal layer.
3. The optical body according to claim 1 , wherein
the light of a specific wavelength band is principally light of a wavelength of 780 nm to 2100 nm.
4. The optical body according to claim 1 , wherein
the ridges have a pointed shape, and
when a height difference between the ridges that rhombically intersect is taken to be ΔX, 0.2 μm<ΔX is satisfied.
5. The optical body according to claim 1 , wherein
the ridges have a spherical shape, and
when a curvature radius of the spherical shape is taken to be Sr and a height difference between the ridges that rhombically intersect is taken to be ΔX, ΔX=0 and 0.3 μm≤Sr≤10 μm are satisfied.
6. A window material comprising the optical body according to claim 1 .
7. A roll screen comprising the optical body according to claim 1 .