| CPC G02B 1/10 (2013.01) [B60R 1/001 (2013.01); G02B 13/14 (2013.01)] | 17 Claims |

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1. A far-infrared ray transmission member comprising:
a base material configured to transmit far-infrared rays; and
a functional film that is formed on the base material, and comprises a low refractive index layer comprising an oxide as a principal component and having a refractive index equal to or smaller than 1.5 with respect to light at a wavelength of 10 μm,
wherein:
a thickness of the far-infrared ray transmission member is equal to or larger than 1.5 mm;
an optical thickness n1d1 of the low refractive index layer, as a product of a thickness d1 and a refractive index n1 with respect to light at a wavelength of 10 μm, is equal to or larger than 0.1 μm and equal to or smaller than 2.5 μm;
the low refractive index layer comprises MgO as a principal component, and a content of MgO is equal to or larger than 50 mass % and equal to or smaller than 100 mass % with respect to the entire low refractive index layer; and
the far-infrared ray transmission member is mounted on a vehicle.
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