Visible-light transmitting solar-heat reflective film

Abstract

It is intended to realize a sheet which is used as a windshield of a building, a vehicle or a house or adhered to window glass, so that it may reflect and shield solar radiation heat rays, which might otherwise become a thermal load on air conditioning, while retaining natural illumination from solar radiation, thereby to have such functions to transmit the visible light and to reflect the heat rays are effective for saving the energy. Provided is a visible light transmitting solar-heat reflecting film, which is made of a multi-layered film including at least one layer of a high refractive index material formed in an optically transparent base material and having a refractive index of 2.0 to 2.6 and a thickness of 10 to 325 nm, and at least one layer of a low refractive index material having a refractive index of 1.8 or less and a thickness of 10 to 325 nm. The solar-heat reflecting film has an average optical transmittance of 60% or more to a light of a wavelength of 400 to 700 nm, and sacrifices the reflectivities of wavelengths near 1115 nm and 1385 nm, at which the energy density on the earth surface is the minimum, due to the absorptions by the water vapor of the atmosphere in the heat ray contained in the solar radiation, thereby improving the average reflectivity for the heat ray of a wavelength of 800 to 1040 nm of a relatively high energy density, to 80% or more, and the average reflectivity for the heat ray of a wavelength of 1150 to 1300 nm, to 50% or more.

Dependencies are inferred from the claim text.